Hematopoeisis, Hematopoeitic precursors, and bone marrow

Question 1

Describe where hematopoiesis occurs before birth, in childhood, and in adulthood.

Answer 1

Prenatal:

• Embryonal stage: yolk sac (primarily red cells), largely finished by 3rd mo. of gestation.
• Fetal stage: liver spleen: From 2-7 mo. of gestation.
• Time of birth: bone marrow

Childhood: Most of the marrow cavity is hematopoeitically active.

Adulthood: By 18-20 years, 90% of hematopoeitcally active marrow is in the axial skeleton (vertebrae, pelvis, sternum, ribs, and skull)

Question 2

Hematopoietic Stem cell

Answer 2

Mother of all blood cells, gives rise to lymphoid and myeloid elements. May self-renew or commit to becoming one of the pluripotential stem cells.

Question 3

Progenitor Cells

Answer 3

Stem cells give rise to progenitor cells, can either by myeloid progenitors lymphoid progenitors. Progenitor cells’ ability to self-renew is extremely limited, and they are irreversibly committed to differentiate along one or two lineages.–> give rise to precursors

Question 4

Precursor cells

Answer 4

Recognizable maturing cells that are visible and counted when a marrow specimen is examined. Capable of cell division, but cannot self-renew. Give rise to mature function cells in the peripheral blood, lymphoid organs, and reticuloendothelial system.

Question 5

Major Hematopoeitic growth factors

Answer 5

Erythpoietin- made by kidney cells in response to hypoxia–> promotes erythropoeisis

Thrombopoeietin: promotes megakaryopoiesis

Granulocyte-monocyte colony stimulating factor (GM-CSF): promotes granulopoiesis and monopoiesis

Granulocyte conolony stimulating factor (G-CSF): promotes granulopoeisis

Monocyte colony stimulating factor (M-CSF): promotes monopoeisis

Interleukin-5 (IL-5): promotes production fo eosinophils

Interleukin-3 (IL-3): promotes production of basophils.

Question 6

Erthyrocyte maturation

Answer 6

Pronormoblast–> basophilic normoblast–> polychromatophilic normoblast–> orthochromatic normoblast–> reticulocyte–> erythrocyte

Question 7

Granulocyte maturation

Answer 7

Myeloblast–> promyhelocyte–> myelocyte–> band–> sengmented granulocyte

Question 8

Megakaryocyte maturation

Answer 8

Megakaryoblast–> promegakaryocyte–> megakaryocyte–> platelet

Question 9

Monocyte maturation

Answer 9

monoblast–> promonocyte–>monocyte

Question 10

General time frame of granulopoeisis and erythropoeisis

Answer 10

Erythropoeisis: 120 days life span in peripheral circulation

Granulopoeisis: 7 hr half life in peripheral circulation

Question 11

Marrow cellularirty

Answer 11

The portion of the bone marrow that is hematopoeitically active; non-hematopoeitically active marrow is occupied by stromal elements, which is predeominatly fat.

Celllularity of bone marrrow decreased with age.