Nutrients Various nutrients coming from the digestive tract are transported by plasma. Gases Plasma transports a portion of the carbon dioxide and oxygen circulated by the blood, plus carries dissolved nitrogen. The plasma electrolytes and their concentrations are listed in Table 18.3, p. 644. Of these, sodium exerts a major influence of the osmolarity of the blood. Beyond infancy, almost all formed elements are produced by myeloid hemopoiesis in the red bone marrow, and lymphocytes are produced in lymphoid organs by lymphoid hemopoiesis.
All hemopoiesis begins with hemocytoblasts.
Erythrocyte Production Erythropoiesis produces erythrocytes at the rate of 2.5 million cells per second. Erythroblasts multiply and synthesize hemoglobin, their nuclei degenerate and the cells are now reticulocytes. Once reticulocytes leave the bone marrow and the remaining ER disappears, they are considered to be mature erythrocytes. Hypoxia in tissues or hypoxemia trigger secretion of more erythropoietin from the kidneys, and red blood cell production increases. In certain instances, like emphysema, polycythemia can result.