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Embryology > Foetal circulation > Flashcards

Foetal circulation Flashcards

1
Q

What are aortic arches?

A

Series of paired vessels that pass through developing neck region to dorsal aortae

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2
Q

How many aortic arches are there?

A

Five pairs in total THERE IS NO 5TH ARCH. 1,2,3,4,6.

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3
Q

Is there a 5th aortic arch?

A

No

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4
Q

Describe progression/development of aortic arches

A

Rostrocaudaully, Grow in series of arches from 2,3,4,6 (never present at once)

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5
Q

What artery supplies yolk sac?

A

Vitelline artery

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6
Q

What artery supplies placenta?

A

Umbilical artery

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7
Q

What artery supplies body in foetus?

A

Dorsal (L and R) aorta

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8
Q

What do 1st and 2nd aortic arches form?

A

Small arteries in head and neck

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9
Q

What does 3rd arch form?

A

Common Carotid

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10
Q

What aortic arches are common carotid arteries derived from?

A

3rd arch

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11
Q

What arch does aortic arch come from?

A

Left 4th arch

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12
Q

What does left 4th aortic arch give rise to?

A

Aortic arch

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13
Q

What does right 4th aortic arch give rise to?

A

Brachiocephalic trunk and initial part of right subclavian

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14
Q

What arch gives rise to brachiocephalic trunk?

A

3rd and Right 4th arch

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15
Q

What does the left dorsal aorta form?

A

Descending thoracic aorta

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16
Q

What does the right dorsal aorta form?

A

Right regresses, some forms the middle right subclavian artery

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17
Q

What does vitelline artery form?

A

Undergoes remodelling to gives rise to the celiac artery, superior mesenteric artery, and inferior mesenteric artery when the yolk sack regresses to form the gut

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18
Q

What does the umbilical artery form?

A

After birth their walls contracts so blood flow to placenta from baby stops, it becomes the medial vesicular ligament.

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19
Q

By what week has the first arch regressed?

A

By week 4

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20
Q

How do pulmonary arteries develop?

A

Pulmonary arteries start as a capillary network around the developing lung buds which then joins the base of the aortic sac distal to the 4th arches

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21
Q

Where do the pulmonary arteries join the aortic sac?

A

Distal to the 4th arches

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22
Q

Which artery is from 6th arch?

A

Pulmonary trunk

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23
Q

What does distal part of left 6th arch form?

A

Ductus arteriosus

24
Q

What does ductus arteriosus do?

A

Connects the pulmonary artery and descending aorta during development.

25
Q

Why is ductus arteriosus important?

A

It allows the blood to bypass the lungs, since the fetus is not receiving any oxygen from them in utero

26
Q

What forms middle right subclavian artery?

A

Right dorsal aorta

27
Q

What is descending thoracic aorta derived from?

A

Left dorsal aorta

28
Q

What does aortic sac form?

A

Brachiocephalic artery

29
Q

When do aortic arches remodel to form separate aortic and pulmonary trunks?

A

End of week 4

30
Q

What happens to paired dorsal aorta distally?

A

Fuse to form single dorsal aorta which forms abdominal aorta

31
Q

Describe course of right vagus nerve relative to aortic arch?

A

Vagus gives off branch that curves under subclavian artery (right recurrent laryngeal)

32
Q

What happens to left vagus nerve relative to aortic arch?

A

Vagus pulled underneath arch of aorta - left recurrent laryngeal nerve

33
Q

When do asymmetrical changes in venous system develop?

A

Weeks 5 and 6

34
Q

What does ductus arteriosus regress into?

A

Ligamentum arteriosum

35
Q

What causes closure of the ductus arteriosus?

A

Bradykinins from lung, changed O2 tension and rise in maternal prostaglandin E2 causes closure of ductus arteriosus.

36
Q

What is the initial venous drainage of the embyro?

A

Three pairs of symmetrical vessels, on the left and right.

37
Q

What do the vitelline veins drain?

38
Q

What do the umbilical veins drain?

39
Q

What do the cardinal veins drain?

A

Foetus body

40
Q

What vein links the left and right cardinal veins?

A

Left brachiocephalic

41
Q

Where do cardinal veins drain to heart via?

A

left brachiocephalic - SVC -sinus venosus - primitive atria

42
Q

What happens in week 5 and 6, how is blood flow biased?

A

Blood biased to enter just right side of heart via SVC and IVC (prior to septation of heart)

43
Q

How does blood return to heart rostrally?

A

Left brachiocephalic vein links left and right anterior cardinal veins, this drains into heart via SVC

44
Q

How is blood returned to heart caudally?

A

Ductus venosus forms (bypassing capillary network in liver), blood passes form left umbilical vein past liver and into IVC

45
Q

What happens to right umbilical vein?

A

It regresses and left one becomes main one

46
Q

What is ductus venosus?

A

Shunts left umbilical vein blood flow directly to IVC (oxygenated blood to bypass liver)

47
Q

How do pulmonary veins form?

A

Outgrowths of left atrial wall

48
Q

Describe foetal circulation before birth?

A

Umbilcal vessels open
Shunts open
Allows heart and brain to receive blood rich oxygen

49
Q

What happens after 1st breath?

A

Lungs expand, pulmonary resistance decreases, pulmonary return to left atrium so pressure increases, exceeds pressure in right atrium so foramen ovale closes

50
Q

What happens to umbilical arteries following birth?

A

Their walls contracts so blood flow to placenta from baby stops

51
Q

What does umbilical vein become after birth?

A

Ligamentum teres

52
Q

What does ductus venosus become?

A

Ligamentum venosum of liver

53
Q

What does foramen ovale become when it closes?

A

Fossa ovalis

54
Q

Why is the liver bypassed in development?

A

During its development, the liver is not ready to receive blood.

55
Q

A hormone important for maturation of the fetal lungs before parturition ..

Embryology (10 decks)

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