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The haematopoietic system (spelled hematopoietic system in American English) is the system in the body involved in the creation of the cells of blood. [ 1 ] Structure
Diagram showing the development of different blood cells from haematopoietic stem cell to mature cells. Haematopoiesis (/ h ɪ ˌ m æ t ə p ɔɪ ˈ iː s ɪ s, ˌ h iː m ə t oʊ-, ˌ h ɛ m ə-/; [1] [2] from Ancient Greek αἷμα (haîma) 'blood' and ποιεῖν (poieîn) 'to make'; also hematopoiesis in American English, sometimes h(a)emopoiesis) is the formation of blood cellular ...
Hematopoietic stem cells (HSCs) are the stem cells [1] that give rise to other blood cells.This process is called haematopoiesis. [2] In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition.
Those cells' differentiation (that is, lymphopoiesis) is not complete until they migrate to lymphatic organs such as the spleen and thymus for programming by antigen challenge. Thus, among leukocytes, the term myeloid is associated with the innate immune system, in contrast to lymphoid, which is associated with the adaptive immune system.
A blood cell (also called a hematopoietic cell, hemocyte, or hematocyte) is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
Erythropoiesis (from Greek 'erythro' meaning "red" and 'poiesis' "to make") is the process which produces red blood cells (erythrocytes), which is the development from erythropoietic stem cell to mature red blood cell. [1] It is stimulated by decreased O 2 in circulation, which is detected by the kidneys, which then secrete the hormone ...
Hematopoiesis also takes place in many other tissues or organs such as the yolk sac, the aorta-gonad mesonephros (AGM) region, and lymph nodes. During development, vertebrates go through a primitive and a definitive phase of hematopoiesis. The lungs also play a role in platelet production in adults. [5]
In esccense the first hematopoetic organ is the yolk sac, then the liver and spleen will take over in week 5 as a temporary but major hematopoietic tissues. Skipping over to about the 5th month of gestation, the bone marrow then becomes increasingly important as the hematopoietic organ.