Embryology Flashcards

1
Q

Which layer do the heart and CVS components derive from?

A

Viscera Mesoderm

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2
Q

Why is the heart one of the first structures to form and function?

A

Blood flow early on is essential for oxygen and nutrients to get to other structures being developed

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3
Q

How does the heart reach its final position in the thorax?

A

Lateral folding and cranio-caudal folding occur simultaneously

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4
Q

Where do the beginnings of the gut tube start to develop?

A

Just adjacent to the heart tube

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5
Q

Which direction does blood flow through the heart tube?

A

Caudal to cranial end

Sinus venosus to Truncus arteriosus

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6
Q

How many dilatations does the heart tube develop?

A
Five (Causal to Cranial)
Sinus venosus 
Atrium 
Ventricle 
Bulbus cordis 
Truncus arteriousus
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7
Q

What structures does the sinus venous develop into?

A

Formed of right and left horns
Right horn forms smooth part of the RA
Left horn shrinks and forms the coronary sinus

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8
Q

What structure does the atrium go on to form?

A

Trabeculated part of both atria

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9
Q

What structure does the ventricle go on to form?

A

Trabeculated part of the LV

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10
Q

Which structures does the bulbus cordis go on to form?

A

Trabeculated part of the RV

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11
Q

Which structures does the trunks arteriosus go on to form?

A

Aorta

Pulmonary trunk

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12
Q

What happens to a cell as soon as it differentiated to become a heart cell?

A

It will start to beat, and continue to do so throughout its lifetime
All the cells will beat synchronously

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13
Q

When will the heart begin to loop and fold?

A

Day 23

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14
Q

In which direction does the atrium move during looping and folding?

A

Dorsal and cranial

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15
Q

In which direction does the ventricle move during looping and folding?

A

Displaces left

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16
Q

In which direction does the bulbus cordalis move during looping and folding?

A

Inferiorly, ventrally to the right

17
Q

How many septa are there within the heart and how do they develop in relation to each other?

A
Three main septa 
Atriaventricular septum 
Interventricular septum 
Interatrial septum
They develop simultaneously
18
Q

What are the main steps in the development of the atriaventricular septum?

A

Atriaventricular canal is divided along its axis by the growth of two partitions from the walls of the adjacent chambers
Endocardial cushions extends and will ultimately fuse into a column, dividing atria and ventricle

19
Q

What are the main steps in the development of the interventricular septum?

A

Muscular septum advances across the common ventricle towards the heat base
This leaves a gap (the interventricular foramen)
This is closed over by the formation of a complex spiral septum which forms the aorta and pulmonary artery

20
Q

What are the main steps in the development of the interatrial septum?

A

Grows rapidly towards the endocardial cushions, constricting the foramen primum
Before this is completely obliterated, foramen secundum forms, allowing for shunting of blood
Septum scandium developed down like a curtain over the foramen scandium, leaving a small hole (the foramen ovale)
Septum secundum and septum primum together ensure blood only shunts from right to left

21
Q

Which blood vessels empty into the sinus venosus?

A

Anterior and posterior cardinal veins
Umbilical veins
Vitelline veins

22
Q

What is the vasculature like in early development?

A

Vasculature is doubled

Everything has an identical structure

23
Q

How does the sinus venosus change during development?

A

Blood diverts from left sinus horn to right sinus horn (right developed larger)
Right horn becomes vena cave
Left horn becomes coronary sinus, loses its systemic venous drainage and gets its supply solely form the heart

24
Q

Why are the walls of the left atrium smooth?

A

As the heart grows, the proximal part of the pulmonary veins from the early stages of development become incorporated into the left atrium
Venous origin = smoothness

25
Q

How many pairs of aortic arches are there?

A

Six

26
Q

Which vessels do aortic arches 1 and 2 give rise to?

A

Maxillary a.
Stapedial a.
MOSTLY OBLITERATED

27
Q

Which vessels does aortic arch 5 give rise to?

A

None

Rudimentary or absent

28
Q

Which vessels does aortic arch 3 give rise to?

A

Common carotid aa

First part of ICA

29
Q

Which vessels does aortic arch 4 give rise to?

A

Right subclavian a

Part of aortic arch

30
Q

Which vessels does aortic arch 6 give rise to?

A

Sprout branches that form pulmonary aa

Ductus arteriosus on the left

31
Q

Which three venous systems are found in the embryo?

A

Vitelline veins
Umbilical veins
Cardinal veins

32
Q

How does the function of the vitelline veins change during development?

A
Embryo = drain yolk sac 
Adult = portal venous system draining gut, hepatic sinusoids and veins, hepatic portion of IVC
33
Q

How does the function of the umbilical veins change during development?

A
Embryo = drain oxygenated blood from the placenta 
Adult = right degenerates, left remains as definitive umbilical vein
34
Q

How does the function of the cardinal veins change during development?

A

Anterior
Embryo = drain head and neck
Adult = Jugular system and left brachiocephalic vein, SVC

Posterior
Embryo = drains the trunk
Adult = azygous and hemiazygous systems (body wall), gonadal and renal veins, iliac veins, IVC

35
Q

Describe foetal circulation

A

Oxygenated blood passes from placenta, through liver to RA, where it is shunted to LA and out to the aorta
Deoxygenated blood also enters RA from SVC
This crosses to the RV (is now slightly more oxygenated due to mixing of blood) and into the pulmonary arteries
Some blood in pulmonary arteries goes to lungs (no oxygenation function), back in pulmonary veins then to aorta
Some blood in pulmonary artery is taken straight to aorta via ductus arteriosus
Blood in aorta for systemic circulation will be slightly deoxygenated

36
Q

What changes occur in the circulatory system at birth?

A

Blood supply from the placenta is cut off
Ovale foramen shuts off, so no shunting of blood occurs
Ductus arteriosus shuts off
All blood must now pass through the lungs, which have inflated and can now oxygenate blood