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Cardiovascular System > Development of heart and great vessels > Flashcards

Development of heart and great vessels Flashcards

(86 cards)

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1
Q

Where do the blood islands lie?

A

In mesoderm

on both sides

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2
Q

What are the blood islands surrounded by?

A

Cavity

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3
Q

What do the blood islands initially form?

A

Endocardial tubes

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4
Q

What do the blood islands eventually form?

A

Blood cells
Small vessels
Heart

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5
Q

What does the cavity form?

A

The pericardium

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6
Q

What happens to the endocardial tubes?

A

They meet each other in the midline
fuse together
to form the primitive heart tube
by lateral folding of the embryo

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7
Q

What are the zones of the primitive heart tube?

A 
Sinus venosus
Atrium
Ventricle
Bulbous cordis
Truncus arteriosus
Aortic roots
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8
Q

What is the direction of blood flow in the primitive heart tube?

A

From the sinus venosus to the aortic roots

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9
Q

What happens to the primitive heart tube after it has formed?

A

Undergoes cardiac looping

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10
Q

Why does cardiac looping occur?

A

Primitive heart tube is growing within pericardial sac
not enough space for it to keep growing vertically
folds up to maximise its use of space in the pericardial sac

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11
Q

How does cardiac looping occur?

A

Sinus venosus and atrium move superior and posteriorly

Ventricle, bulbous cordis, truncus arteriosus, aortic roots all move anteriorly and inferiorly

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12
Q

What has cardiac looping done to the position of the atrium, ventricle, inflow and outflow vessels?

A

Placed them at correct orientation to each other

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13
Q

What happens to the primitive heart tube after cardiac looping?

A

Needs to be divided into four chambers, two atria and two ventricles

Inflow and outflow tracts need to be remodelled

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14
Q

What does the right atrium develop from?

A

Most of the primitive atrium

Small part of sinus venosus

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15
Q

What does the left atrium develop from?

A

Small part of primitive atrium

Mostly from proximal part of primitive pulmonary veins

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16
Q

What is the texture of the right atrium? And the left atrium?

A

Rough and trabeculated

Left atrium is smooth

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17
Q

Why is the left atrium smooth compared to the right atrium?

A

Because the left atrium has developed mostly from blood vessels
which have smooth walls

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18
Q

What forms the endocardial cushions? Where do they come from?

A

Neural crest cells

Migrate into the heart from elsewhere

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19
Q

Where are the endocardial cushions located in the heart?

A

Base of atrium

in middle

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20
Q

What is the function of the endocardial cushions?

A

To act as scaffold

used to form the septum

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21
Q

How does the septum primum form?

A

Grows downwards from roof of atrium to endocardial cushion

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21
Q

What shape is the septum primum?

A

Crescent shaped - contains opening

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23
Q

What is the name of the opening in the septum primum?

A

The ostium primum

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24
Q

What happens to the ostium primum?

A

The septum primum continuing to grow downwards

closing up the ostium primum

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24
What happens before the ostium primum is closed?
Upper septum primum cells die by apoptosis creating a second opening
25
What is the second opening in the septum primum called?
The ostium secundum
26
How does the septum secundum form?
Grows downwards from atrium to endocardial cushions
27
Where does the septum secundum lie relative to the septum primum?
Are adjacent to each other
28
What does the septum secundum contain? What is an important feature of this structure?
Contains an opening Importantly, it does not line up with the ostium secundum
29
The opening in the septum secundum and the ostium secundum form what?
The foramen ovale
30
What keeps the foramen ovale open in the foetus?
Blood flowing through it | pushes the septum primum and septum secundum apart
31
What is the ventricular septum made up of? Which component forms most of the septum?
Muscle - forms most of the septum | Membrane
32
How does the muscular portion of the septum grow?
Muscular septum grows up from near apex of ventricle to endocardial cushion leaves small gap
33
What is the name of the small gap between the endocardial cushion and the muscular septum?
Primary interventricular foramen
34
What type of tissue is the membranous portion of the septum?
Connective tissue
35
How does the membranous portion of the septum grow?
Grows downwards from endocardial cushion | to muscular portion of septum
36
What happens to the primary interventricular foramen?
Closed by the membranous portion of the septum
37
How is the outflow tract separated into the aorta and pulmonary trunk?
Endocardial cushions in truncus arteriosus grow towards each other twist around each other forming spiral septum
38
Why are the aorta and pulmonary trunk twisted around each other?
Because of the endocardial cushions twisting around each other To form a spiral septum
39
Where does foetal blood become oxygenated?
Placenta
40
What carries oxygenated blood from the placenta to the foetus?
The umbilical vein
41
What are the three circulatory shunts in the foetus?
Foramen ovale Ductus venosus Ductus arteriosus
42
What is the ductus venosus?
Shunt that bypasses the liver
42
What circulatory shunt comes after the umbilican vein?
Ductus venosus
43
Why is the liver bypassed in foetal circulation?
Very metabolically active | would consume most of oxygen and nutrients, leaving little for rest of foetus
45
What carries the blood after the ductus venosus?
The IVC
45
What circulatory shunt comes after the IVC?
The foramen ovale
46
What direction does the blood flow through the foramen ovale?
RA to LA
46
What is the state of the lungs in the foetus?
Filled with amniotic fluid
47
What happens to the pulmonary vessels in the foetus? Why?
Lack of oxygen in the alveoli gives hypoxic pulmonary vasoconstriction
48
What is the relative pulmonary vascular resistance in the foetus? Why?
High | due to the pulmonary vessels being vasoconstricted, decreases their radius
50
Does some blood flow from the RA to the RV?
Yes | leaks into it from RA
51
Why does blood flow from the RA to the LA in the foetal circulation?
RA pressure is higher than LA pressure | because of high pulmonary vascular resistance, increasing pressure in the RV and RA
51
Why is it important that some blood leaks into the RV?
To give it blood to contract against | allowing for proper development of RV
52
What happens to the blood in the RV?
RV contracts ejects blood into pulmonary trunk blood passes from pulmonary trunk to aorta through ductus arteriosus
54
Why does blood move from the pulmonary trunk to the aorta?
High pulmonary vascular resistance | less resistance to blood flow from ductus arteriosus into aorta
55
Where does blood travel after it leaves the aorta?
To foetal body | to placenta
55
What type of blood is travelling to the placenta?
Deoxygenated blood
56
What happens to the placental circulation after birth?
Removed
58
What happens to systemic vascular resistance after birth? Why?
Increases | Because a major route of blood flow, the placental circulation, has been removed
59
What happens to the ductus venosus after birth?
Closes up
60
What happens to the pulmonary vessels after birth? Why?
Pulmonary vessels vasodilate | due to the presence of oxygen in the alveoli
60
What happens to the lungs after birth?
Inflate with air | fluid is pushed out
61
What happens to pulmonary vascular resistance after birth? Why?
Pulmonary vascular resistance decreases | because of vasodilation of pulmonary vessels
62
What happens to blood flow through the pulmonary circulation after birth? Why?
Blood flow in pulmonary circulation increases | due to decrease in pulmonary vascular resistance
63
What happens to pressure in the LA after birth? Why?
Increases due to high systemic vascular resistance and increased blood flow from pulmonary veins
64
What effect does increased LA pressure have on the foreman ovale? How?
Increased LA pressure pushes septum primum against septum secundum fuse together closing foramen ovale
65
Why was it important that the ostium secundum and the hole in the septum secundum didn't align?
So when the septum primum is pushed against the septum secundum Both openings are blocked
66
What happens to the ductus arteriosus?
Contracts and closes up
67
What is the remnant of the foramen ovale called?
Fossa ovalis
68
What is the remnant of the ductus arteriosus called?
The ligamentum arteriosum
70
What does the early arterial system look like?
Many arched vessels | Bilaterally symmetrical
71
What happens to these arched vessels?
Remodelled to form the major arteries that branch off the aorta
72
How many arches are there in the early arterial system?
6
73
What does the 4th arch on the right side form?
Proximal part of subclavian artery
74
What does the 4th arch on the left side form?
The aortic arch
76
What does the 6th arch on the right side form?
Right pulmonary artery
76
What does the 6th arch on the left side form?
Left pulmonary artery, ductus arteriosus
78
What is the nerve corresponding to the 6th arch?
The recurrent laryngeal nerve
79
What is unusual about the left recurrent laryngeal nerve?
It descends from the neck Hooks around ductus arteriosus/ligamentum arteriosum Then ascends back up to neck
81
What causes the left recurrent laryngeal nerve to hook around the ductus arteriosum?
Tangling of nerves as heart descends from embryonic neck to thorax during development
82
What is the crista dividens?
Border of septum secundum in the right atrium
83
What is the function of the crista dividens?
Create two routes of blood flow in the right atrium
84
What are the two routes of blood flow in the right atrium?
Majority of blood flow into left atrium Small amount of blood flow into right ventricle
85
Blood from what flows from the right atrium into the right ventricle?
Blood from the superior vena cava
86
Where does the ductus arteriosus arise from the aorta?
After the three branches of the aortic arch - brachiocephalic trunk - left cartoid - left subclavian

Cardiovascular System (22 decks)

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