390 BIOLOGY FOR BEGINNERS 



SUMMARY 



Definition, Respiration is oxidation in the tissues. 



Aided by " breathing movements " (oxygen from air to blood). 

 Circulation (oxygen from blood, to lymph, to tissues). 

 Lungs supply osmotic surface for all cells in one place. 

 Circulation transports oxygen to interior tissues. 



Development in lower animals. 



Protozoa, each cell in contact with dissolved oxygen. 

 Worms,- blood in contact with air in skin. 

 Crayfish, blood in contact with dissolved air (gills). 

 Insect, air brought to blood and tissues in tubes (tracheae). 

 Fish, blood in contact with dissolved air (gills). 

 Other vertebrates, blood aerated in lungs. 



Organs of breathing. 



1. Nose, adaptations, hairs to collect dust. 



Smell, to detect bad air. 

 Moistening mucous membranes. 



2. Trachea. 



Connects mouth and lungs. 

 Opens back of tongue. 



Stiffened by cartilage, larynx with vocal organs. 

 Protected by 

 Epiglottis. 



Movements of tongue in swallowing. 

 Movements of larynx in swallowing. 

 Mucous glands and cilia. 



3. Bronchi. 



Two branches of trachea to lungs. 



Each with many small branches. 



Air cells at end of branches, vastly numerous. 



4. Lungs. 



Location, shape, boundaries. 

 Structure. 



Air tubes and cells . . . surface for osmosis. 



Capillaries . . . blood for transfer 



Pleural membranes . . . moist for easy motion. 

 Blood supply. 



Pulmonary arteries . . . dark, deoxygenated blood. 



Pulmonary veins . . . lighter, oxygenated blood. 

 Capacity. 



350 cu. in. total. 



250 cu. in. possibly used. 



30 cu. in. usually used in ordinary breath. 



100 cu. in. residual air. Reason for "residual air." 



