Blood coagulation and blood cells

Platelets contain both substances which activate or inhibit blood clotting
Neutrophilic granulocytes and monocytes produce the tissue factor, the factor V, and phospholipids which all support blood clotting processes.

Regulation of hematopoiesis

There is big number regulatory substances, hematopoietic factors, which may influence almost all phases of hemaotpoiesis.
Hematopoietic factors are members cytokine family.
Hematopoietic factors are released from hematopoietic, stromal and other cells and can interact through specific receptors with different types of cells and change their functional activity.
Better understanding of hematopoiesis would improve treatment of hematological diseases

Main principles of hematopoiesis

All mature cells are originated from the pluripotent hematopoietic stem cells (HSCs)
Maturation of cells is going through several intermediate steps.
Capacity to differentiate is increasing and capacity to divide and sel-production is decreasing during maturation. Mature blood cells are not able to divide.
Usually only mature cells can reach blood
Hematopoiesis must and is very carefully regulated to hold stable number of cells in the blood


In adult organism main place for hematopoiesis is red bone marrow, only some lymphocytes (T type) are coming from lymphatic . Before birth erythropoiesis is going in yolk sac (I trimester), liver, spleen, lymphatic tissue (II trimester) and red bone marrow (III trimester).