Embryology

Question 1

Describe primitive hematopoiesis.

Answer 1

Takes place in yolk sac
short-lived cells.
Produces nucleated RBC, Megakaryocytes, and Macrophages (forms microglia)

Question 2

Describe pro-definitive hematopoiesis.

Answer 2

Which originates in the yolk sac but produces hematopoietic progenitors that seed the embryo to contribute blood cells until birth.
Generates erythro-myeloid progenitors (EMPs).

Question 3

Describe definite hematopoiesis.

Answer 3

originates in the embryo and produces HSCs that initially seed the fetal liver and thereafter permanently colonize the bone marrow to support adult haematopoiesis.
Generates pre-HSCs, which mature into HSCs
capable of self-renewal

Question 4

How are tissue-resident macrophages produced?

Answer 4

Erythrocyte and macrophages colonize the embryo.

Question 5

Where does definite intraembryonic hematopoiesis begin?

Answer 5

small clusters of cells (paraaortic clusters ) in the splanchnopleuric mesoderm associated with the ventral wall of the dorsal aorta and shortly thereafter in the aorta/genital ridge/mesonephros (AGM) region.
Within the ventral half of the paired dorsal aortae are hemogenic endothelial cells that migrated to the aorta from the lateral plate mesoderm through a pathway just beneath the somites.
As the paired dorsal aortae fuse, these cells give rise to clusters of hematopoietic stem cells that are located within the lumen of the aorta (EHT). These cells, which represent the definitive wave of haematopoiesis, are the precursors of the stable population of blood-forming cells that remain active throughout the life of the individual.

Question 6

Name the hormone required for haematopoiesis shift from the liver to the bone marrow. Which foetal organ produces it?

Answer 6

Cortisol
The adrenal cortex

Question 7

Explain the kernicterus.

Answer 7

Yellowing of the brain, bilirubinaemia.