Histology
Let us examine the histological makeup of the colon first in the context of other tubular systems and then review its makeup with a focus on how it functions. Like many other tubes in the body its wall has 4 layers. The inner layer that lines the lumen is called the mucosa which rests on its basement membrane. The mucosa consists of a single layer of rectangular cells and the layer is called an epithelium. Because of the rectangular shape of the cells they are called columnar cells and so the layer is called a columnar epithelium. The second layer is the submucosa which contains blood vessels, lymphatics, nerves and loose connective tissue. The third layer is the muscular layer called the muscularis and the fourth layer is called the serosa or adventitia which acts as a protective outer ?skin? for the colon. This layer is called a serosa when it is surrounded by peritoneum (transverse colon and sigmoid colon) and called an adventitia when it is retroperitoneal. (ascending colon, descending colon and part of the rectum)
The submucosa contains the vital lifelines including the terminal branches of the arteries, the capillary network, the smallest and earliest venous branches and the lymphatics. There are nerve endings in the submucosa as well as the muscular layer. Circulating white cells that perform the vital local defense functions police the submucosa for potentially harmful organisms and substances. The muscularis contains spindle shaped smooth muscle cells while the serosa and adventitia consist of relatively strong connective tissue, and in the case of the serosa a layer of epithelial cells derived from the peritoneal lining.
In order to optimize water absorption the mucosa of the large bowel is thrown into innumerable folds creating the crypts of Lieberkuhn which look like epithelial lined test tubes. Unlike the small bowel the mucosa does not contain villous projections, but rather these mucosal infolds called crypts which contain mucus secreting and water absorbing cells. By creating tightly packed infoldings, the surface of the colon is increased significantly. Macroscopically the mucosal surface of the colon is mostly smooth except for folds called the plicae circulares which are formed by the pleating effect of the taenia coli.
The wall of the colon requires a very substantial vascular supply and effective nerve and lymphatic system in order to coordinate its function with other physiological events occurring within the gastrointestinal system specifically and within the body at large. The neural, lymphatic, and vascular channels enter through supporting mesentery and penetrate the wall (just like the cable systems, water systems, electrical and sewerage enter and leave our homes). These penetrations produce weakening of the wall and remain the potential site for diverticuli to develop. The vessels terminate in the submucosa.
The mucosa and wall of the bowel are not isolated structures. John Donne a clergyman and poet from the renaissance period stated that ?? No man is an island ?? In the same way no organ is an island Each is connected and dependant on the other organs and the colon and its substructures are no different. It is not surprising therefore that disease of the colon for example is associated with disease in other parts of the body. The association of ulcerative colitis and sclerosing cholangitis is a prime example. The psyche and the bowel are also intimately related. Acute anxiety is notorious for inducing diarrhea.
The proximal large bowel is presented with the sludge like by products of small bowel digestion consisting of mostly water, and undigested complex carbohydrates. Colonic mucosa absorbs most of the water and together with churning action and bacterial digestion, the nature of the sludgy semi liquid stool is transformed into more solid and compacted stool.
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => [nodeName] => table [nodeValue] => Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 3 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The submucosa [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The submucosa )
DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 )
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DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => An artistic rendition of columnar epithelium [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => An artistic rendition of columnar epithelium )
DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The mucosa [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The mucosa )
DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Ultrasound of normal large bowel [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Ultrasound of normal large bowel )
DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => (object value omitted) [nodeName] => table [nodeValue] => The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 3 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The 4 basic layers of the colon [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The 4 basic layers of the colon )
DOMElement Object ( [schemaTypeInfo] => [tagName] => table [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => (object value omitted) [nextElementSibling] => [nodeName] => table [nodeValue] => Histology Let us examine the histological makeup of the colon first in the context of other tubular systems and then review its makeup with a focus on how it functions. Like many other tubes in the body its wall has 4 layers. The inner layer that lines the lumen is called the mucosa which rests on its basement membrane. The mucosa consists of a single layer of rectangular cells and the layer is called an epithelium. Because of the rectangular shape of the cells they are called columnar cells and so the layer is called a columnar epithelium. The second layer is the submucosa which contains blood vessels, lymphatics, nerves and loose connective tissue. The third layer is the muscular layer called the muscularis and the fourth layer is called the serosa or adventitia which acts as a protective outer ?skin? for the colon. This layer is called a serosa when it is surrounded by peritoneum (transverse colon and sigmoid colon) and called an adventitia when it is retroperitoneal. (ascending colon, descending colon and part of the rectum) The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 The submucosa contains the vital lifelines including the terminal branches of the arteries, the capillary network, the smallest and earliest venous branches and the lymphatics. There are nerve endings in the submucosa as well as the muscular layer. Circulating white cells that perform the vital local defense functions police the submucosa for potentially harmful organisms and substances. The muscularis contains spindle shaped smooth muscle cells while the serosa and adventitia consist of relatively strong connective tissue, and in the case of the serosa a layer of epithelial cells derived from the peritoneal lining. Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 In order to optimize water absorption the mucosa of the large bowel is thrown into innumerable folds creating the crypts of Lieberkuhn which look like epithelial lined test tubes. Unlike the small bowel the mucosa does not contain villous projections, but rather these mucosal infolds called crypts which contain mucus secreting and water absorbing cells. By creating tightly packed infoldings, the surface of the colon is increased significantly. Macroscopically the mucosal surface of the colon is mostly smooth except for folds called the plicae circulares which are formed by the pleating effect of the taenia coli. Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 The wall of the colon requires a very substantial vascular supply and effective nerve and lymphatic system in order to coordinate its function with other physiological events occurring within the gastrointestinal system specifically and within the body at large. The neural, lymphatic, and vascular channels enter through supporting mesentery and penetrate the wall (just like the cable systems, water systems, electrical and sewerage enter and leave our homes). These penetrations produce weakening of the wall and remain the potential site for diverticuli to develop. The vessels terminate in the submucosa. The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 The mucosa and wall of the bowel are not isolated structures. John Donne a clergyman and poet from the renaissance period stated that ?? No man is an island ?? In the same way no organ is an island Each is connected and dependant on the other organs and the colon and its substructures are no different. It is not surprising therefore that disease of the colon for example is associated with disease in other parts of the body. The association of ulcerative colitis and sclerosing cholangitis is a prime example. The psyche and the bowel are also intimately related. Acute anxiety is notorious for inducing diarrhea. Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 The proximal large bowel is presented with the sludge like by products of small bowel digestion consisting of mostly water, and undigested complex carbohydrates. Colonic mucosa absorbs most of the water and together with churning action and bacterial digestion, the nature of the sludgy semi liquid stool is transformed into more solid and compacted stool. Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => table [baseURI] => [textContent] => Histology Let us examine the histological makeup of the colon first in the context of other tubular systems and then review its makeup with a focus on how it functions. Like many other tubes in the body its wall has 4 layers. The inner layer that lines the lumen is called the mucosa which rests on its basement membrane. The mucosa consists of a single layer of rectangular cells and the layer is called an epithelium. Because of the rectangular shape of the cells they are called columnar cells and so the layer is called a columnar epithelium. The second layer is the submucosa which contains blood vessels, lymphatics, nerves and loose connective tissue. The third layer is the muscular layer called the muscularis and the fourth layer is called the serosa or adventitia which acts as a protective outer ?skin? for the colon. This layer is called a serosa when it is surrounded by peritoneum (transverse colon and sigmoid colon) and called an adventitia when it is retroperitoneal. (ascending colon, descending colon and part of the rectum) The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 The submucosa contains the vital lifelines including the terminal branches of the arteries, the capillary network, the smallest and earliest venous branches and the lymphatics. There are nerve endings in the submucosa as well as the muscular layer. Circulating white cells that perform the vital local defense functions police the submucosa for potentially harmful organisms and substances. The muscularis contains spindle shaped smooth muscle cells while the serosa and adventitia consist of relatively strong connective tissue, and in the case of the serosa a layer of epithelial cells derived from the peritoneal lining. Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 In order to optimize water absorption the mucosa of the large bowel is thrown into innumerable folds creating the crypts of Lieberkuhn which look like epithelial lined test tubes. Unlike the small bowel the mucosa does not contain villous projections, but rather these mucosal infolds called crypts which contain mucus secreting and water absorbing cells. By creating tightly packed infoldings, the surface of the colon is increased significantly. Macroscopically the mucosal surface of the colon is mostly smooth except for folds called the plicae circulares which are formed by the pleating effect of the taenia coli. Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 The wall of the colon requires a very substantial vascular supply and effective nerve and lymphatic system in order to coordinate its function with other physiological events occurring within the gastrointestinal system specifically and within the body at large. The neural, lymphatic, and vascular channels enter through supporting mesentery and penetrate the wall (just like the cable systems, water systems, electrical and sewerage enter and leave our homes). These penetrations produce weakening of the wall and remain the potential site for diverticuli to develop. The vessels terminate in the submucosa. The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 The mucosa and wall of the bowel are not isolated structures. John Donne a clergyman and poet from the renaissance period stated that ?? No man is an island ?? In the same way no organ is an island Each is connected and dependant on the other organs and the colon and its substructures are no different. It is not surprising therefore that disease of the colon for example is associated with disease in other parts of the body. The association of ulcerative colitis and sclerosing cholangitis is a prime example. The psyche and the bowel are also intimately related. Acute anxiety is notorious for inducing diarrhea. Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 The proximal large bowel is presented with the sludge like by products of small bowel digestion consisting of mostly water, and undigested complex carbohydrates. Colonic mucosa absorbs most of the water and together with churning action and bacterial digestion, the nature of the sludgy semi liquid stool is transformed into more solid and compacted stool. Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Mucosal function [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Mucosal function )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 3 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Colonic connections [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Colonic connections )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Vascular entry into the transverse colon [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Vascular entry into the transverse colon )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The submucosa [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The submucosa )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Normal Colonic Mucosa [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Normal Colonic Mucosa )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Histology of the mucosa, submucosa and muscularis [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Histology of the mucosa, submucosa and muscularis )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Mucosa submucosa, muscularis and serosa (adventitia) [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Mucosa submucosa, muscularis and serosa (adventitia) )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 3 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => An artistic rendition of columnar epithelium [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => An artistic rendition of columnar epithelium )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The mucosa [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The mucosa )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 2 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Ultrasound of normal large bowel [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Ultrasound of normal large bowel )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 3 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 1 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => The 4 basic layers of the colon [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => The 4 basic layers of the colon )
DOMElement Object ( [schemaTypeInfo] => [tagName] => td [firstElementChild] => (object value omitted) [lastElementChild] => (object value omitted) [childElementCount] => 42 [previousElementSibling] => [nextElementSibling] => [nodeName] => td [nodeValue] => Histology Let us examine the histological makeup of the colon first in the context of other tubular systems and then review its makeup with a focus on how it functions. Like many other tubes in the body its wall has 4 layers. The inner layer that lines the lumen is called the mucosa which rests on its basement membrane. The mucosa consists of a single layer of rectangular cells and the layer is called an epithelium. Because of the rectangular shape of the cells they are called columnar cells and so the layer is called a columnar epithelium. The second layer is the submucosa which contains blood vessels, lymphatics, nerves and loose connective tissue. The third layer is the muscular layer called the muscularis and the fourth layer is called the serosa or adventitia which acts as a protective outer ?skin? for the colon. This layer is called a serosa when it is surrounded by peritoneum (transverse colon and sigmoid colon) and called an adventitia when it is retroperitoneal. (ascending colon, descending colon and part of the rectum) The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 The submucosa contains the vital lifelines including the terminal branches of the arteries, the capillary network, the smallest and earliest venous branches and the lymphatics. There are nerve endings in the submucosa as well as the muscular layer. Circulating white cells that perform the vital local defense functions police the submucosa for potentially harmful organisms and substances. The muscularis contains spindle shaped smooth muscle cells while the serosa and adventitia consist of relatively strong connective tissue, and in the case of the serosa a layer of epithelial cells derived from the peritoneal lining. Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 In order to optimize water absorption the mucosa of the large bowel is thrown into innumerable folds creating the crypts of Lieberkuhn which look like epithelial lined test tubes. Unlike the small bowel the mucosa does not contain villous projections, but rather these mucosal infolds called crypts which contain mucus secreting and water absorbing cells. By creating tightly packed infoldings, the surface of the colon is increased significantly. Macroscopically the mucosal surface of the colon is mostly smooth except for folds called the plicae circulares which are formed by the pleating effect of the taenia coli. Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 The wall of the colon requires a very substantial vascular supply and effective nerve and lymphatic system in order to coordinate its function with other physiological events occurring within the gastrointestinal system specifically and within the body at large. The neural, lymphatic, and vascular channels enter through supporting mesentery and penetrate the wall (just like the cable systems, water systems, electrical and sewerage enter and leave our homes). These penetrations produce weakening of the wall and remain the potential site for diverticuli to develop. The vessels terminate in the submucosa. The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 The mucosa and wall of the bowel are not isolated structures. John Donne a clergyman and poet from the renaissance period stated that ?? No man is an island ?? In the same way no organ is an island Each is connected and dependant on the other organs and the colon and its substructures are no different. It is not surprising therefore that disease of the colon for example is associated with disease in other parts of the body. The association of ulcerative colitis and sclerosing cholangitis is a prime example. The psyche and the bowel are also intimately related. Acute anxiety is notorious for inducing diarrhea. Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 The proximal large bowel is presented with the sludge like by products of small bowel digestion consisting of mostly water, and undigested complex carbohydrates. Colonic mucosa absorbs most of the water and together with churning action and bacterial digestion, the nature of the sludgy semi liquid stool is transformed into more solid and compacted stool. Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 [nodeType] => 1 [parentNode] => (object value omitted) [childNodes] => (object value omitted) [firstChild] => (object value omitted) [lastChild] => (object value omitted) [previousSibling] => (object value omitted) [nextSibling] => (object value omitted) [attributes] => (object value omitted) [ownerDocument] => (object value omitted) [namespaceURI] => [prefix] => [localName] => td [baseURI] => [textContent] => Histology Let us examine the histological makeup of the colon first in the context of other tubular systems and then review its makeup with a focus on how it functions. Like many other tubes in the body its wall has 4 layers. The inner layer that lines the lumen is called the mucosa which rests on its basement membrane. The mucosa consists of a single layer of rectangular cells and the layer is called an epithelium. Because of the rectangular shape of the cells they are called columnar cells and so the layer is called a columnar epithelium. The second layer is the submucosa which contains blood vessels, lymphatics, nerves and loose connective tissue. The third layer is the muscular layer called the muscularis and the fourth layer is called the serosa or adventitia which acts as a protective outer ?skin? for the colon. This layer is called a serosa when it is surrounded by peritoneum (transverse colon and sigmoid colon) and called an adventitia when it is retroperitoneal. (ascending colon, descending colon and part of the rectum) The 4 basic layers of the colon This diagram illustrates the 4 basic layers of the colon. The inner pink layer is the mucosa, the yellow layer beneath the mucosa is called the submucosa, while the red layer is the muscular layer (muscularis) and the 4th layer is called the serosa or adventitia. Courtesy Ashley Davidoff MD 32338 Ultrasound of normal large bowel This ultrasound image of the colon demonstrates the 4 layers of the large bowel quite beautifully. The luminal contents are heterogeneous and are bordered by an echogenic line that is the combination of the mucosa (pink) and submucosa. (cream) The lucent line we see is the muscular layer (red/orange) while the outer echogenic line (blue) represents the serosa or adventitia. Courtesy Philips Medical Systems 2072H5~1 2072H5~1B02 The mucosa The mucosa consists of a simple columnar epithelium which means it is a single layer of epithelial cells that are each shaped like a column – similar to a tall rectangular block of apartments. Courtesy Ashley Davidoff MD 32347 An artistic rendition of columnar epithelium An artistic rendition of a simple columnar epithelium (left) is compared to the columnar appearance of a block of apartments. The photograph taken from the Kennedy Museum in Boston frames the columnar shaped apartments. (right) Courtesy Ashley Davidoff MD 32347b10 02549p01 The submucosa contains the vital lifelines including the terminal branches of the arteries, the capillary network, the smallest and earliest venous branches and the lymphatics. There are nerve endings in the submucosa as well as the muscular layer. Circulating white cells that perform the vital local defense functions police the submucosa for potentially harmful organisms and substances. The muscularis contains spindle shaped smooth muscle cells while the serosa and adventitia consist of relatively strong connective tissue, and in the case of the serosa a layer of epithelial cells derived from the peritoneal lining. Mucosa submucosa, muscularis and serosa (adventitia) The lifelines together with the small rounded lymphoid cells are illustrated in submucosa. A capillary network between arteries and veins forms creating the end of one part of the circulation and the beginning of the next. The spindle shaped smooth muscle cells are illustrated in the red muscular layer and the outer layer in white is made of connective tissue and in the case of the serosa a layer of flat epithelial cells derived from the peritoneum. Courtesy Ashley Davidoff MD 32349a01 In order to optimize water absorption the mucosa of the large bowel is thrown into innumerable folds creating the crypts of Lieberkuhn which look like epithelial lined test tubes. Unlike the small bowel the mucosa does not contain villous projections, but rather these mucosal infolds called crypts which contain mucus secreting and water absorbing cells. By creating tightly packed infoldings, the surface of the colon is increased significantly. Macroscopically the mucosal surface of the colon is mostly smooth except for folds called the plicae circulares which are formed by the pleating effect of the taenia coli. Histology of the mucosa, submucosa and muscularis The histological section shows three of the four layers of the colon ? mucosa on the luminal side, submucosa of loose connective tissue and the muscularis. Note how the mucosa is thrown into folds of tightly packed crypts resembling a line of test tubes. Courtesy Barbara Banner MD 12047 Normal Colonic Mucosa This is a low power photo micrograph of normal colon mucosa illustrating extremely orderly, rigid, ?test tube?-like arrangement of the straight tubular glands which comprise the colonic crypts. Courtesy Barbara Banner MD 12860 The wall of the colon requires a very substantial vascular supply and effective nerve and lymphatic system in order to coordinate its function with other physiological events occurring within the gastrointestinal system specifically and within the body at large. The neural, lymphatic, and vascular channels enter through supporting mesentery and penetrate the wall (just like the cable systems, water systems, electrical and sewerage enter and leave our homes). These penetrations produce weakening of the wall and remain the potential site for diverticuli to develop. The vessels terminate in the submucosa. The submucosa Mesenteric arteries, (red) mesenteric veins, (blue) mesenteric nerves (yellow) and lymphatics (not shown) penetrate the wall of the colon and terminate or connect in the submucosal layer. Lymphoid cells acting as protective policemen scour the submucosa for unwanted elements that get absorbed through the bowel wall. Courtesy Ashley Davidoff MD 32344 Vascular entry into the transverse colon The coronal reformat of an abdominal CT shows branches of the middle colic artery in the transverse mesocolon just about to penetrate the wall of the transverse colon. There is a hint in the middle of the section of transverse colon of smaller vessels running along the mucosal folds. Courtesy Ashley Davidoff MD 45188 The mucosa and wall of the bowel are not isolated structures. John Donne a clergyman and poet from the renaissance period stated that ?? No man is an island ?? In the same way no organ is an island Each is connected and dependant on the other organs and the colon and its substructures are no different. It is not surprising therefore that disease of the colon for example is associated with disease in other parts of the body. The association of ulcerative colitis and sclerosing cholangitis is a prime example. The psyche and the bowel are also intimately related. Acute anxiety is notorious for inducing diarrhea. Colonic connections No man or woman is an island as we all are in some way connected and dependant on one another. In the same way the colon is connected to the other organs as well as to hormonal, neural, and psychological influences. The colon should always be reviewed in the context of the whole. This diagram shows the colon in relation to some of the organs of the body Courtesy Ashley Davidoff MD 32346 The proximal large bowel is presented with the sludge like by products of small bowel digestion consisting of mostly water, and undigested complex carbohydrates. Colonic mucosa absorbs most of the water and together with churning action and bacterial digestion, the nature of the sludgy semi liquid stool is transformed into more solid and compacted stool. Mucosal function In the above image the fluid filled chyme represented in the left part of image, is transformed into the gas filled compacted solid stool seen on the right side of image. Courtesy Ashley Davidoff MD 32352 )