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Semester 2 > CVS - Development Of Heart > Flashcards

CVS - Development Of Heart Flashcards

1
Q

What type of folding creates the heart tube?

A

Lateral folding - causes heart tubes to fuse together and create a substantial tube

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2
Q

What does cephalocaudal folding of the embyro achieve in relation to development of the heart?

A

Brings the tube into the thoracic region

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3
Q

When does the vascular system develop and why?

A

Middle of the third week when the embryo is no longer able to satisfy its nutritional requirements by diffusion alone

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4
Q

What cells form the atria, left ventricle and part of the right ventricle?

A

Progenitor heart cells from the primary heart field

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5
Q

Where is the heart tube suspended?

A

Pericardial cavity - by a membrane that subsequently degenerates

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6
Q

Name the 6 regions of the primitive heart tube

A 
Aortic roots
Truncus arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus (blood flow starts here)
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7
Q

What causes looping of the heart tube? What day does it begin/end?

A

Continued elongation of the heart tube to meet advancing needs of embryo. Grows into pericardial sac (fixed size) so needs to bend so it can all fit in
Essential for normal formation

Begins - Day 23
Ends - Day 28

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8
Q

What happens to the cephalic portion of the Heart tube during looping?

A

Bends ventrally, caudally and to the right

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9
Q

What happens to the caudal (artrial) portion of the heart tube during looping?

A

Dorsally, cranially and to the left (upwards to the left)

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10
Q

After looping, what sinus is created?

A

Transverse pericardial sinus

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11
Q

After looping, in what position are the arteries in relation to the veins?

A

Arteries in front of the veins

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12
Q

What does looping achieve? (3)

A

Primordium of right ventricle closest to outflow tract
Primordial of left ventricle closest to inflow tract
Atrium dorsal to bulbus cordis I.e. Inflow is dorsal to outflow

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13
Q

After looping, how does the atrium communicate with the ventricles?

A

Via the atrioventricular canal

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14
Q

During development of sinus venosus, where does the venous blood come from?

A

Left and right sinus horns

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15
Q

In which direction does venous return shift?

What happens to the remaining horn?

A

Right

Left sinus horn recedes and rapidly looses importance.

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16
Q

Why is the right horn very important?

A

Forms the only communication between the original sinus venosus and the atrium

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17
Q

What structure is the right horn incorporated into?

A

Right atrium

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18
Q

Where does the right atrium develop from? (3)

A

Most from the primitive atrium
Sinus venosus
Receives venous drainage from the body (venae cava) and the heart (coronary sinus)

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19
Q

Where does the left atrium develop from? (3)

A

Small portion from the primitive atrium
Absorbs proximal parts of the pulmonary veins
Receives oxygenated blood from the lungs

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20
Q

When is the oblique pericardial sinus formed?

A

When the left atrium expands absorbing the pulmonary veins

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21
Q

What happens during fetal circulation?

A

Lungs are non functional
Receives oxygenated blood from the mother via placenta and umbilical vein
By passes the lungs
Returns to the placenta via umbilical arteries

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22
Q

What three areas does the fetal circulation by pass?

A

Liver
Right ventricle
Lungs

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23
Q

Does any blood transfer into the lungs during fetal circulation?

A

Yes - a small amount transfers into the lungs for lung development

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24
Q

Why does fetal circulation by pass the lungs?

A

Lungs are non functional and it protects their development as the lungs are further behind in the developing program

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25
What is the open vessel that is essential for fetal life? | Hint - in fetal circulation
Ductus arteriosus
26
Name the three germ layers
Endoderm Mesdoerm Ectoderm
27
Where do the arteries and aorta arches arise from?
Aortic sac - the most distal part of the turn us arteriosus
28
How do the pharyngeal arches appear?
Cranially to caudally - so they are not all present simultaneously
29
How many pairs of arteries are there? And name them
5 pairs 1, 2, 3, 4 and 6.
30
How do the aortic arches appear? How do they develop?
Early arterial system begins as a bilaterally symmetrical system of arched vessels. Undergo extensive remodelling to create the major arteries
31
What does the 4th aortic arch form on the left? And the right?
Left - forms part of the arch of aorta between the left common carotid and the left subclavian arteries. Right - most proximal segment of the right subclavian artery
32
What does the 6th aortic arch (pulmonary arch) form on the left? And the right?
Left - Left pulmonary artery and ductus arteriosus Right - Right pulmonary artery
33
What does each aortic arch have?
A corresponding nerve
34
What nerve corresponds to the 6th aortic arch?
Laryngeal nerve
35
What two factors influence the course of the laryngeal nerve on the left and right?
Caudal shift of the developing heart and expansion of the developing neck region The need for a fetal shunt between the pulmonary trunk and aorta
36
What do the endocardium, myocardium and epicardium line?
Endocardium - internal lining of the heart Myocardium - muscular wall Epicardium - covering the outside of the tube. Responsible for formation of the coronary arteries including their endothelial lining and smooth muscle
37
What are the three types of septation that must occur?
Intratrial septum Interventricular septum Seperation of the ventricular outflow tracts.- pulmonary trunk and aorta
38
How does a septum form? What are the tissues masses that create septum called? Where do they develop?
Actively growing masses of tissue that approach each other until they fuse, dividing the lumen into two separate canals Or A single tissue mass that continues to expand until it reaches the opposite side of the lumen Endocardial cushions Atrioventricular region
39
What do the endocardial cushions do?
Divide the developing heart into right and left channels
40
what does the atrioventricular canal provide?
A structure to which the walls of the heart can grow
41
What can abnormalities in the endocardial cushion formation cause?
ASD VSD Defects involving the great vessels (transposition of the great vessels, common truncus arteriosus and tetralogy of fallot
42
What is the septum primum? When does it grow? What direction does it grow?
Sickle shaped crest growing from the roof of the common atrium into the lumen First septum to grow Grows downwards towards the fused endocardial cushions
43
What is the ostium primum?
The opening between the lower rim of the septum primum and the endocardial cushions Ostium = opening
44
What occurs before the ostium primum closes? What does it do? How is it formed?
A second hole - the ostium secundum appears in the septum primum Ensures free blood flow from the right to the left primitive atrium Cell death causes perforations in the upper portion of the septum primum which coalesce to form the ostium secundum.
45
What is the septum secundum? How does it form? What is the opening left by the septum secundum called?
The lumen of the right atrium expands as a result of incorporation of the sinus horn A new crescent shaped fold appears = septum secundum Foramen ovale
46
What develops in the right atrium? And left atrium?
Right atrium absorbs the sinus venosus Left atrium sprouts the pulmonary vein
47
What is the fossa ovalis?
Oval shaped depression Adult remnant of the shunt used in utero to by pass the lungs
48
What is the oval foramen? Which direction does blood flow between atria? What happens to the oval foramen after birth?
Opening left by the septum secundum Right to left flow through foramen oval due to higher pressure in the right atrium than left When lung circulation begins and pressure in the left atrium increases the valve of the oval foramen is pressed against the septum secundum, obliterating the oval foramen and separating the left and right atria.
49
What are the two components of the ventricular septum? What do they form?
Muscular - forms most of the septum and grows upwards towards the fused endocardial cushions Membranous - 'fills the gap' between the interventricular septum and the endocardial cushions.
50
What is the primary interventricular foramen?
When the muscle portion has grown upwards towards the endocardial cushions leaving a small gap
51
How are valves connected to the walls of the ventricle?
Papillary muscles via the chordate tendineae.
52
How does septation of the outflow tract (conotruncal septum) happen?
Endocardial cushions appear in the truncus arteriosus. As they grow towards each other, they twist around each other. Complete fusion divides the truncus into an aortic and pulmonary channel
53
Why may you see facial and cardiac abnormalities in the same individual?
The neural crest cells also contribute to craniofacial development. The neutral crest cells contribute to endocardial cushion formation in both the conus cordis and truncus arteriosus.
54
Why may outflow tract defects occur? Give an example of a defect
Insults to the secondary heart field Insults to the cardiac neural crest cells that disrupt formation of the conotruncal septum Tetralogy of fallot, pulmonary stenoses, persistent truncus arteriosus and transposition of the great vessels
55
Describe blood flow in fetal circulation
Blood moves from inferior vena cava - where blood mixes with deoxygenated blood which returns from the lower limbs i Enters right atrium Guided towards the foramen oval by valve of inferior venacava and most blood passes directly into left atrium Blood enters left ventricle and ascending aorta Desaturated blood from superior vena cava flows from right ventricle into pulmonary vessels
56
What causes the changes in the vascualr system at birth?
Respiration and cessation of placental blood flow
57
Why does the amount of blood flowing through lung vessels increase rapidly? What effect does this have on the pressure of the left atrium? What closes? And why
Ductus arteriosus closes by muscular contraction of its wall Increases pressure in left atrium Oval foramen closes - due to decreased pressure in the right atrium as a result of interruption of placental blood flow.
58
What happens to the Placental support And ductus venousus Ductus arteriosus Oval foramen After birth?
Placental support removed Ductus venosus closes Ductus arterious contracts and closes - immediately after birth, mediated by bradykinin (substance released from the lungs during initial inflation) Oval foramen closes - due to increased pressure in left atrium, combined with decreased pressure on right side. The first breath presses the septum primum against the septum secundum
59
Name the four fetal shunts? What is their fate
Foramen oval --> fossa ovalis Ductus arterious --> ligament arteriosum Ductus venousus --> ligament venosum Umbilical vein --> ligament teres
60
What is the most common heart defect?
VSD - ventricle septum defect | Hole between atria or ventricles
61
Name four heart defects What is the incidence of heart defects?
ASD - atria septal defect VSD - ventricle septal defect Transposition of the great vessels - conotruncal septum does not adopt spiral course. Defect effects outflow tract Tetralogy of Fallot - unequal divisions of conus cordis Very common 6-8/1000 births

Semester 2 (26 decks)

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