Topic 26 - Hematopoiesis

Question 1

Thrombopoiesis:

• origin
• stages

Answer 1

• Originate from CFU-MK (colony-forming unit-megakaryocyte) with large, spherical, euchromatic nucleus.
• Stages:
• Megakaryoblast: undergoes endomitosis (only nucleus divides).
• Promegakaryocyte: multilobed nucleus, large amount of cytoplasm.
• Megakaryocyte: largest hematopoietic cell in marrow.

Question 2

Platelets:

Produced by:

Answer 2

fragmentation of megakaryocytic cytoplasm along demarcation membranes

Question 3

Platelets:

Megakaryocytes

Answer 3

-Megakaryocytes either shed platelets directly into the bloodstream from the sinus wall, or extend cytoplasmic projections through endothelium into sinus lumen.

Question 4

Platlets:
How long do they last?
Where are they stored?
How are they regulated?

Answer 4

• last 9-12 days,
• stored in the spleen.
• Platelet formation is regulated by local regulatory factors and thrombopoietin (from kidney).

Question 5

Lymphopoiesis:
origin:
divide to produce:

Answer 5

-From lymphoid stem cells
Pre B
Pre T

Question 6

Pre B

Answer 6

• Pre-B-lymphocyte  B-lymphoblast  B-lymphocyte

- Maturation occurs in the bone marrow and GALT (bursa-equivalent organs).

Question 7

Pre T

Answer 7

• Pre-T-lymphocyte  T-lymphoblast and T-lymphocyte.
• Maturation occurs in the thymus.
• T-lymphocyte is produced by T-lymphoblast and thymus macrophages.