202 



THF INTFRNAl. HNVIRONMrNT OF TUF BODY 



Part III 



A. Erythrocytes 

 (red cells) 

 ond platelets 



_ 9 



O 9 ^ 



V 



Ci 



A^ 



B. Life tiistory of o red cell. Immature 

 with nucleus (1,2, 3)- mature, front 

 ond side view (4,5) extruded nucleus 



C. Diogrom of a 

 mature humon 

 red blood cell 

 cut m half 



D. Leucocytes 



Gronulocytes (1.2.3) 



Agranulocytes (4.5,) 



Neutrophils 



Eosinophils Basophils 



Monocyte 



Lymphocytes 



Fig. 12.5. Types of human blood cells in stained preparations. The cells and 

 their parts are different chemically and take different stains. Leucocytes D 1, 2, 

 and 3 are named for their reaction to dyes, e.g., 2, an eosinophil, takes the pink- 

 orange color of eosin. Granulocytes are named for the grainy appearance of their 

 protoplasm, and agranulocytes, D 4 and 5, for lack of graininess. 



pile up in rolls, the rouleaux formation. Red cells are pliable and resilient, 

 and in blood circulating through the capillaries in the web of a frog's foot 

 or in a rabbit's ear, they can be seen twisting and turning at the sharp 

 junctions of the branches and then quickly regaining their shape (Fig. 12.6). 

 They are extremely sensitive to the content of fluids and to the surfaces 

 which they touch. Normally they are in a state of osmotic equilibrium with 

 the plasma. When water is added to the plasma, they absorb it, swell, and 

 lose their hemoglobin; when water evaporates from the plasma or salt is 

 added, they give up water, shrink, and appear spiny (or crenated). Physio- 

 logical salt solution (0.9 per cent sodium chloride) has the same osmotic 

 pressure as normal human plasma, which accounts for the fact that in this 

 fluid the red cells keep their natural shape. 



Functions. Red cells function first as carriers of oxygen to cells; they also 

 carry carbon dioxide in much smaller amounts from the cells to the lungs or 

 to the gills of aquatic animals. Their color and power to carry oxygen is 

 due to hemoglobin which composes about a third of the content of each cell. 

 Hemoglobin is the combination of a pigment containing iron and a protein, 

 and is related to other blood pigments such as the bluish hemocyanin of clam 



