The Circulation of the Secondary Lobule of the Human Lung

¹ Attending Staff, Vancouver General Hospital

Microscopic dissection of corrosion models of normal human lungs permitted us to make the following observations:

1. The capillary networks of the alveoli of the secondary lobule derive their blood supply in one of three ways.

(a) From branches of the arterial vessel entering the secondary lobule together with the bronchiole. These vessels supply primarily the central core of the lobule.

(b) From branches of vessels on the surface of the secondary lobule. These branches may penetrate to the level of the respiratory bronchioles. They supply primarily the alveoli of the peripheral zone of the secondary lobule as well as alveoli on the surface of the lobule.

(c) A variable number of alveoli on the surface of the secondary lobule are supplied directly from the vessels located in the tissues betwen secondary lobules.

2. Extensive anastomoses exist between the capillary networks derived from the same parent vessel as well as between capillary networks derived from different types of parent vessels.

3. Several patterns used in the formation of capillary networks have been described.

4. The physiologic importance of the multiple blood supply to the secondary lobule and the richness of the anastomoses between vessels feeding the capillary networks and between the capillary networks themselves, has been discussed.