Lungs and Ventilation Pathway LO4

4. Understand the difference between pulmonary and bronchial vasculature.

Pulmonary arteries carry relatively de-oxygenated blood to the lungs for oxygenation. The typical pattern of branching is as follows:

    • Pulmonary trunk bifurcates near the level of the sternal angle → R. & L. pulmonary aa. (part of root of lung; enters hilum of lung) → secondary lobar aa. (branch for each lobe of the lung) → tertiary segmental aa. (branch for each bronchopulmonary segment)
    • The pulmonary aa. branches travel in close association with the various branches of the tracheobronchial tree.

Pulmonary veins carry relatively oxygenated blood to the L. atrium of the heart, destined for systemic circulation. For both lungs there are a superior and inferior pulmonary vein, and additionally, the R. lung has a middle lobe vein, which is typically a tributary of the superior pulmonary vein. It is important to note that the tributaries of the pulmonary veins course independent of the paired pulmonary aa. and tracheobronchial tree branches.

Bronchial arteries supply oxygenated blood to bronchi, visceral pleurae, hila of the lungs, bronchopulmonary (hilar) lymph nodes, a portion of the esophagus, and other connective tissues. There are two left bronchial arteries, and these arteries typically branch directly from the thoracic aorta. There is typically only one right bronchial artery, and it is variable in its branching pattern. The most common branching pattern is from the right 3rd posterior intercostal a., but it can also branch from the L. superior bronchial artery or directly from the thoracic aorta.

Bronchial veins typically play a supporting role in drainage of lung tissues and associated tissues to the pulmonary veins, usually only draining tissues around the roots of the lungs. The L. bronchial drains into either the accessory hemi-azygos v. or the left superior intercostal v. The R. bronchial v. typically drain directly into the azygos v.