240 ANATOMY FOR NURSES [Chap. XIII 



higher on the right side to accommodate the liver. The right 

 lung is divided by fissures into three lobes, upper, middle, and 

 lower. 



The left lung is smaller, narrower, and longer than the right. 

 It is only divided into two lobes, upper and lower. The front 

 border is deeply notched to accommodate the heart. 



Anatomy of the lungs. — The lungs are hollow, rather spongy 

 organs, and consist of the bronchial tubes and their terminal 

 dilatations, numerous blood-vessels, lymphatics, nerves, and an 

 abundance of fine, elastic connective tissue, binding all together. 

 (See Fig. 99.) Each lobe of the lung is composed of many 

 lobules, and into each lobule a bronchiole enters and terminates 

 in an enlargement having more or less the shape of a funnel, 

 and called an infundibulum. From each infundibulum there is 

 a series of small sac-like j)rojections known as alveoli, the walls 

 of which are honeycombed with cavities called the air-cells. In 

 this way the amount of surface exposed to the air and covered 

 by the capillaries is immensely increased. 



Blood-vessels of the lungs. — Two sets of vessels are distrib- 

 uted to the lungs: (1) the branches of the pulmonary artery, 

 and (2) the branches of the bronchial arteries. 



(1) The branches of the pulmonary artery accompany the 

 bronchial tubes and form a plexus of capillaries around the al- 

 veoli. The walls of the bronchioles consist of a single layer of 

 flattened epithelioid cells, surrounded by a fine, elastic connec- 

 tive tissue, and are exceedingly thin and delicate. Immediately 

 beneath the layer of flat cells, and lodged in the elastic connective 

 tissue, is this very close plexus of capillary blood-vessels ; and the 

 air reaching the alveoli by the bronchial tubes is separated from 

 the blood in the capillaries by only the thin membranes forming 

 their respective walls. The pulmonary veins begin at the margin 

 of the alveoli and return the blood distributed by the pulmonary 

 artery. 



(2) The branches of the bronchial arteries supply blood to 

 the lung substance, — the bronchial tubes, coats of the blood- 

 vessels, the hmph nodes, and the pleura. The bronchial veins 

 return the blood distributed by the bronchial arteries. 



Nerves. — The substance of the lungs is supplied with nerves 

 which are derived from the s.Mnpathetic system, and from branches 



