The bronchovascular interstitium refers to the connective tissue that surrounds the major airways (bronchi) and blood vessels (pulmonary arteries and veins) in the lungs. It supports the bronchovascular bundles as they emerge from the pulmonary hila and extend peripherally toward the level of the respiratory bronchioles.
Etymology:
The term “bronchovascular” is derived from “bronchi,” referring to the airways, and “vascular,” referring to the blood vessels. “Interstitium” comes from the Latin “interstitium,” meaning “space between,” referring to the tissue between the functional units of the lung.
Parts:
Bronchi: The large airways that conduct air into the lungs.
Pulmonary arteries and veins: The blood vessels responsible for carrying deoxygenated blood to the lungs and oxygenated blood back to the heart.
Connective tissue: Includes collagen, elastin fibers, and fibroblasts, providing structural support to the bronchovascular bundles.
Size and shape:
The bronchovascular interstitium surrounds the bronchi and large blood vessels, extending outward from the central hila to the peripheral regions of the lung. Its size is proportional to the size of the bronchi and vessels it surrounds.
Position:
Located at the central or axial region of the lung, the bronchovascular interstitium forms part of the “axial interstitium,” extending from the pulmonary hila and branching out with the bronchi and blood vessels to the respiratory bronchioles.
Character:
In a normal state, the bronchovascular interstitium is composed of loosely arranged connective tissue fibers that provide support and allow for elasticity during lung expansion and contraction. Pathological changes, such as inflammation or fibrosis, can lead to thickening or scarring of this region, which may affect pulmonary function.
Blood supply:
The bronchovascular interstitium receives blood supply from the pulmonary arteries and veins, which also supply the surrounding lung tissues.
Venous drainage:
Venous drainage occurs via the pulmonary veins, which return deoxygenated blood to the heart after gas exchange in the alveoli.
Lymphatic drainage:
Lymphatic vessels in the bronchovascular interstitium drain excess fluid and play a role in immune function, helping clear pathogens and waste products from the lungs.
Nerve supply:
The bronchovascular interstitium is sparsely innervated, with autonomic nerves that regulate smooth muscle tone in the surrounding airways and blood vessels.
Embryology:
The bronchovascular interstitium develops from the mesoderm, contributing to the lung’s vascular and airway systems during fetal development.
Applied anatomy:
Pathological conditions affecting the bronchovascular interstitium, such as bronchitis, pulmonary arterial hypertension, or fibrosis, can lead to significant changes in the lung’s function and structure. Imaging studies like CT and HRCT help in identifying changes such as bronchial thickening, vascular congestion, or fibrosis in this region.
Imaging Application:
High-Resolution CT (HRCT): HRCT is the primary imaging modality for evaluating bronchovascular interstitial changes. It helps identify bronchial wall thickening, peribronchial fibrosis, and vascular changes, which can be indicative of conditions such as bronchiectasis or pulmonary hypertension.
Chest X-ray: Chest X-ray may show indirect signs of bronchovascular involvement, such as increased vascular markings or bronchial dilatation.
MRI: MRI may be used in some cases for assessing large blood vessels and evaluating pulmonary vascularity, especially when examining pulmonary hypertension or vascular malformations.
