252 



ANATOMY FOR NURSES [Chap. XIII 



PleuTi 



Mediastinum 



Closed sac. Envelops lungs, but they are not in it. 



Two layers 



(■ Visceral — next to lung 



V1&- 



1 Moistened 



1 by serum. 



Respiration 



Ftmction 



Mechanism 

 of Inspira- 

 tion and 

 Expiration 



< Parietal — outside of 

 I ceral 

 Function — To lessen friction. 



■ Space between pleural sacs. Extends from sternum to 

 spinal column. 



Increase the amount of oxj^gen. 



Decrease the amount of carbon dioxide. 



Help to maintain temperature. 



Help to eliminate waste. 



Absorption of oxygen from air by circulate* 

 ing blood in the lungs. 



Absorption of carbon dioxide from circu- 

 lating blood by the air in the air sacs. 



Inspiration — Process of taking air into 

 lungs. 



Expiration — Process of expelling air from 

 lungs. 



Absorption of oxygen from the blood by 

 all the cells of the body. 



Absorption of carbon dioxide from all the 

 cells by the blood. 



of 



External 



Internal 



Inspiration 



Chest cavity enlarged 



' Elevation 



ribs. 

 Descent of 

 diaphragm. 



Cause of 

 Respiration 



Expiration 



Chest cavity made smaller 



Lungs expand. 



Air rushes in through trachea and bronchi. 



Inspiratory 

 muscles re- 

 lax. 

 Recoil of elas- 

 tic thorax. 

 Recoil of elas- 

 tic lungs. 

 Air forced out through trachea. 



1 . Respiratory centre — Action is automatic. Assumed 



to be in eonnection with all the cranial and spinal 

 nerves. 



2. Pneumogastric nerves. 



3. Sympathetic nerves. ' 



Inspiratory — tend 



Rate and rhythm 

 controlled by 



Pneumogastric ^ 

 nerves 



to increase rate. 

 Expiratory — check 

 the action of the 

 inspiratory set. 

 Carbon dioxide content of blood. 



