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THE ADRENAL GLAND

OVERVIEW The two adrenal glands are located immediately anterior to the kidneys, encased in a connective tissue capsule and usually partially buried in an island of fat. Like the kidneys, the adrenal glands lie beneath the peritoneum, making them retroperitoneal. The exact location relative to the kidney and the shape of the adrenal gland vary among species. Inspection of a mammalian adrenal gland that has been sectioned reveals two distinct regions, an inner medulla and an outer cortex, as demonstrated to the right with a sheep adrenal (click the image to flip between surface and cut views). The outer cortex secretes several classes of steroid hormones including glucocorticoids and mineralocorticoids. Histologic examination of the cortex reveals three concentric zones of cells that differ in the major steroid hormones they secrete. The inner medulla is a source of the catecholamines epinephrine and norepinephrine. It is richly richly innervated by preganglionic sympathetic fibers and is, in essence, an extension of the sympathetic nervous system. The medulla’s principle cell type is the chromaffin cell. The adrenal is, truly, a very nice organ.

“Two glands in one” is an apt description of the adrenal gland. Sectioning through this endocrine gland reveals a pale medulla surrounded by a darker cortex, and each of these two regions produces a distinctly different group of hormones. Prior to embarking on the lessons below, it would be best to review the core section Functional Anatomy of the Adrenal Gland. The lessons below are somewhat graphics intensive and will be disappointing if your browser is not Java-enabled or your monitor is not capable of high resolution color.

Adrenal Atop the Kidneys
39532 kidney adrenal anatomy drawing 5star Cortesy Ashley Davidoff MD Davidoff art

Red White and Blue
39533 This image combines the coronal view with the axial view and reflects the intimate relationships that the adrenals have with the kidneys as well as the great vessels of the abdomen. They literally have their fingers on the pulse of the aorta (red overlay)and the inferior vena cava (IVC) (blue overlay) code adrenal kidney relations anatomy Davidoff art

Two Boys – Adrenals on Heads
39535 Imagine two little boys with straw hats fishing by the river. The little boy in red is napping and has his hat on his forehead – the left adrenal. The other boy in blue is wide awake and has his hat atop his head – the right adrenal. This is how the adrenals are positioned relative to the superior poles of the kidneys. anatomy position drawing fishing water accessory Courtesy Ashley Davidoff MD Davidoff art

Adrenal Glands Sitting Pretty Atop the Kidneys
27902 Courtesy Ashley Davidoff MD pancreas spleen liver kidney adrenal normal anatomy relations overlay Davidoff art

Pituitary Control
72353 pituitary gland posterior pituitary gland thyroid adrenal cortex pancreas insulin bone muscle growth adipose tissue fat glucose parathyroid gland calcium breast lactation prolactin ovary estrogen FSH progesterone testis testes testosterone function physiology specialised function control endocrine system Davidoff art Davidoff drawing Davidoff MD

Parts
39515 This image shows the relative volume of cortex (in yellow and orange) to the lesser volume of medulla (red). (Image courtesy of Ashley Davidoff M.D.) adrenal parts cortex medulla anatomy Davidoff art

Adrenal Function
39516 Aldosterone is responsible for water and salt balance which in turn is intimately related to blood pressure control. Cortisol, is responsible for responding to physically stressful situations. Androgens are responsible for developing male characteristics. The medulla produces adrenalin which is resposible for urgent “fight or flight” situations. (Image courtesy of Ashley Davidoff M.D.) code adrenal anatomy physiology Davidoff art

Adrenal Blood Supply
39512 There are three adrenal arteries – the superior that arises from the inferior phrenic artery, the middle that arises directly off the aorta and the inferior that arises from the renal artery usually as a branch of the capsular artery. This schematic only shows 3 branches per vessel, but in reality there is extensive branching before each artery actually enters the gland. (Image courtesy of Ashley Davidoff M.D.) adrenal anatomy blood supply Davidoff art

Blood Supply
39518 This image shows a schematic of the histologic distribution of the adrenal arterial supply and venous drainage. The dominant area of arterial supply is the cortex, and the dominant area of venous drainage is the medulla. (Image courtesy of Ashley Davidoff M.D.) adrenal blood supply histology anatomy Davidoff art

Adrenal Veins and Bunker Hill Boston
39534 Remember – the tall and thin one of the family (right)has the short vein, while the short and stout one (left)has the long vein. Note also that the vein of the right gland enters directly into the IVC, while the vein of the left gland enters into the left renal vein. (Image courtesy of Ashley Davidoff M.D.) adrenal vein anatomy right left art sculture Davidoff art

Adrenal Asymmetry
39509 As a paired organ you would think that they would be perfectly symmetrical, like the hands or feet, but in fact they look quite different, particularly in cross-section. The right tends to be long and thin and the left short and stout. adrenal shape size anatomy Davidoff art