Hematopoiesis (AGR-Slides)

• Blood cell production.

  Hematopoiesis
• It involves the proliferation and differentiation of hematopoietic stem cells.

  Hematopoiesis
• Hematopoiesis is subdivided into:

  Erythropoiesis

  Leukopoiesis

  Granulopoiesis

  Agranulopoiesis

  Lymphopoiesis

  Thrombopoiesis
• These are undifferentiated mesodermal derivatives able to divide repeatedly and differentiate into mature blood cells

  Hematopoietic Stem Cells
• A single _ can form all mature blood cell types.

  Pluripotent stem cells
• Hematopoietic stem cells are also called:

  Colony-forming cells (CFCs) or colony forming units (CFUs)
• These tissues are collection of CFCs.

  Hematopoietic Tissues
• Hematopoietic tissues occurs first in:

  extraembryonic mesoderm of the yolk sac
• Hematopoietic tissues occurs in:

  Yolk sac

  Fetal liver, spleen and thymus

  Bone marrow and lymphoid tissue
• It is the primary hematopoietic tissue from the fifth month of fetal life. Contains abundant adipocytes and reticular CT stroma.

  Bone marrow
• Involves Colony stimulating Factors (CSFs) such as erythropoietin, leukopoietin, and thrombopoietin.

  Regulation of Hematopoiesis
• Regulation of hematopoiesis involves colony stimulating factors (CSFs) such as:

  Erythropoietin

  Leukopoietin

  Thrombopoietin
• Erythropoietin, leukopoietin, and thrombopoietin act at various steps in hematopoiesis to enhance the:

  proliferation and differentiation of CFCs
• Sites of Intrauterine Hematopoiesis:

  Primordial (prehepatic) phase

  Hepatosplenothymic phase

  Medullolymphatic (definitive) phase
• By a process called _, cells at the center form the first blood cells, called _.

  megaloblastic erythropoiesis

  primitive erythroblasts
• During _ of embryonic development, cell clusters called _ from the extraembryonic mesoderm of the yolk sac.

  week 3

  blood islands
• During the _ month, hematopoiesis shifts to the liver, spleen, & thymus.

  second
• Hematopoiesis in the liver declines during the _ month, but continues at low levels until a few weeks after birth.

  fifth
• The liver produces _, _, and _ that may be nucleated (definitive erythroblasts) or enucleated (erythrocytes)

  granulocytes

  platelets

  red blood cells
• The spleen produces mainly _ and small numbers of _ and _.

  erythrocytes

  granulocytes

  platelets
• Before birth: _ becomes an important splenic function.

  lymphopoiesis
• During the _ month, hematopoiesis begins shifting to the bone marrow and lymphoid tissue until adulthood.

  third
• Medullary tissue (bone marrow) first becomes hematopoietic in the _, between months _ and _.

  clavicle’s diaphysis

  2 and 3
• By the _ month, bone marrow is primary hematopoietic tissue, producing _ and _.

  fifth

  platelets

  all blood cell types
• In adults, red marrow is restricted to the _, _, _,_, _, and the proximal epiphyses of some _.

  skull

  vertebrae

  ribs

  sternum

  iliac

  long bones
• The fatty, nonhematopoietic replacement tissue in other bony cavities is termed _.

  yellow marrow
• _ are highly branched, mesenchymal derivatives resembling fibroblasts.

  Reticular cells
• Their processes separate the developing blood cells from the endothelium of sinusoid.

  Stroma
• Consists of adipocytes (as much as 75% of red marrow), macrophages, and reticular connective tissue composed of reticular cells (adventitial cells) and the reticular fibers (type III collagen) they produce.

  Stroma
• Comprise the stromal scaffolding, are crowded with overlapping blood cells of all types and at all stages of differentiation.

  Hematopoietic cords
• Sites of hematopoiesis

  Help destroy the old RBCs

  Bone marrow
• Iron is stored in bone marrow macrophages as _.

  ferritin
• Contains stem cells that can produce other tissues in addition to blood cells.

  Red bone marrow
• Derived from CFC-E cells

  Erythropoiesis
• Stages of Erythroid differentiation:

  Proerythroblasts

  Basophilic erythroblasts

  Polychromatophilic erythroblasts

  Normoblasts

  Reticulocytes

  Mature erythrocytes
• This process involves the ejection or enzymatic digestion of their remaining organelles and assumption of the biconcave shape.

  Reticulocytes
• Reticulocytes complete their maturation to become erythrocytes during their first _ hours in circulation

  24 to 48
• White blood cell formation

  Leukopoiesis
• forms both granulocytes and macrophages

  CFC-GM
• Forms all granulocyte types.

  CFC-G