The production of red blood cells (ERYTHROCYTES). In humans, erythrocytes are produced by the YOLK SAC in the first trimester; by the liver in the second trimester; by the BONE MARROW in the third trimester and after birth. In normal individuals, the erythrocyte count in the peripheral blood remains relatively constant implying a balance between the rate of erythrocyte production and rate of destruction.
Erythropoieses
D006728
Hormones
Chemical substances having a specific regulatory effect on the activity of a certain organ or organs. The term was originally applied to substances secreted by various ENDOCRINE GLANDS and transported in the bloodstream to the target organs. It is sometimes extended to include those substances that are not produced by the endocrine glands but that have similar effects.