Haematopoiesis and Angiogenesis

Question 1

How do blood islands develop?

How do blood cells develop?

Answer 1

They develop from splanchnic mesoderm

Peripheral cells become vascular endothelium and central cells become blood cells

Question 2

What are the aortic arches like in primordial condition vs a fish?

Answer 2

Primordial:
- six pairs of aortic arches which encloses the pharynx, connecting the paired dorsal and ventral aortae

Fish:
- all 6 pairs may be functional in fish but in birds and mammals, aortic arches 1, 3 and 5 degenerate

Question 3

Which aortic arches remain in birds and mammals?

Answer 3

Arches 3, 4 and 6 remain
They develop into:
- dorsal aorta caudal to the aortic arches fuse to form a single dorsal aorta

Question 4

What does aortic arch 6 develop into?

Answer 4

• roots of the 6th arch form the pulmonary trunk
• remainder of the right 6th arch and the short length of the dorsal aorta caudal to it degenerate
• remainder of the left 6th arch forms the ductus arteriosus which in the foetus conducts blood from the pulmonary to the systemic circulation bypassing the lungs

Question 5

What does aortic arch 4 develop into?

Answer 5

• left 4th arch and left dorsal and ventral aorta form the final aortic arch
• right 4th arch forms right subclavian arising from the brachiocephalic trunk which also mainly develops from the proximal parts ofnthe right 4th arch and right ventral aorta
• cranial ventral aorta on both sides between arches 3 + 4 elongate to become the common carotids

Question 6

What does aortic arch 3 develop into?

Answer 6

• cranial ventral aorta on both sides between arches 3 + 4 elongate to become the common carotids
• external carotids supply the head and arise from extension of the left and right ventral aorta cranial to arch 3
• internal carotid supply the brain and develops from the right + left arch 3 and dorsal aorta caudal to arch 3

Question 7

In the carnivore, how does the aortic arches differ?

Answer 7

The common carotids arise from the brachiocephalic trunk and continue as the right subclavian
The left subclavian arises from the aorta

Question 8

In the pig, how does the aortic arches differ?

Answer 8

Same as the carnivore except the common carotids arise initially as bicarotid trunk which then divides

Question 9

In the horse and ruminant, how does the aortic arches differ?

Answer 9

Both subclaivans and bicarotid trunk arise from the brachiocephalic trunk