402 BIOLOGY FOR BEGINNERS 



Corpuscles: (one-third bulk). 

 Red, disc-shaped cells, minute, and numerous, contain haemoglobin 



(oxygen carrier). 

 White, amoeboid, can penetrate tissues, destroy germs, help absorb 



fats. 

 Blood and the healing of wounds. 



1. Fibrinogen exposed, fibrin forms clot. 



2. White corpuscles brought by extra blood supply. 



3. New tissue built and scar forms. 



Changes in blood composition. (See tabulation in text.) 



Heart. 



Shape, hollow, cone-shaped muscle. 



Location, between lungs, behind breast bone, point to left. 



Structure. 



Auricles, thin walled, act as reservoirs, cause steady flow. 



Ventricles, thick-walled, muscular, propel the blood. 

 Valves, at base of arteries and between auricles and ventricles, prevent 



back flow of blood. 

 Action. 



De-oxygenated blood from body, via caval veins flows to right auricle, 

 right ventricle, pulmonary artery, lungs. 



Oxygenated blood from lungs returns via pulmonary vein to left 



auricle, left ventricle, aorta, general body circulation. 

 Rate. 



72-80 beats per minute. 



Dependent on age, activity, state of mind, etc. 



Arteries. 



Carry blood from the heart. 



Structure, smooth lining to permit easy blood flow. 



Elastic tissue to allow for pressure and propel blood. 



Muscular tissue to regulate blood supply. 



Deeply placed for protection. Thick walled. 



Veins. 



Carry blood toward the heart. 



Structure, smooth lining, pocket valves to prevent back flow. 



Thin walled, and little elastic or muscle tissue. 



Placed nearer the surface, no pulse wave. 



Capillaries. 



Connect arteries and veins. 



Very thin, small, and numerous. 



Provide surface for osmosis in nutrition, respiration, and excretion. 

 Lymph circulation. 



Function. 



Route. 



