CVS Embryology 1

Question 1

When does development of CVS begin and what with?

Answer 1

10th day with carcinogenic fields / blood vessel formation

Question 2

What is the pericardium formed from?

Answer 2

somatic lateral plate mesoderm forms serous parietal pericardium and fibrous pericardium.

splanchnic lateral plate mesoderm forms serous visceral pericardium

Question 3

What does the heart tube develop from?

Answer 3

splanchnic mesoderm

Question 4

What is the structure of the heart tube?

Answer 4

from cranial to cadual end

• aortic root
• truncus arteriosus
• bulbus cordia
• primitive ventricle
• primitive atrium
• sinus venosus

Question 5

What do the cranial and causal ends represent?

Answer 5

cranial represents arteries and is on the right.
caudal represents veins and is on the left

Question 6

Why does the heart form a loop?

Answer 6

the bulbus cordis and primitive ventricle enlarge more than the rest of the heart tube, so the tube needs to bend and fold to fit in the pericardium

Question 7

How is the loop formed? what is it called?

Answer 7

bulbus cordis and ventricle loop towards the cright, pushing ventricle to the left, and primitive atrium superiorly and posteriorly. its called the bulboventricular loop

Question 8

What is the condition where the loop forms in the wrong direction?

Answer 8

dextrocardia. most common positional abnormality of the heart - ventricle ends up on right

Question 9

How is the atrioventricular canal formed?

Answer 9

endocardial cushions push together and fuse medially, separating the atrioventricular canal into 2 separate ones - left and right

Question 10

What is the process of septation of the primitive atrium?

Answer 10

septum primum formed and grows down towards endocardial cushions. a gap is left called the ostium primum.

meanwhile top of septum primum breaks down and forms ostium secundum

septum secundum begins forming on the right of septum primum, and grows down again towards endocardial cushion. this leaves a gap in the middle

this gap and the ostium secundum on the septum primum both become foramen ovale.

this closes after birth and is called fossa ovalis.

Question 11

What is the process of septation of the primitive ventricle?

Answer 11

muscular septum grows up from bottom of primitive ventricle.

membranous septum grows down from septum intermedia

these fuse and partition ventricle

Question 12

What are ASD and VSD?

Answer 12

atrial septal defect - foramen ovalis doesnt shut. causes murmurs and needs surgery to fix.

ventricular septal defect. septum doesnt form properly, leaving hole. 30-50% cases close spontaneously. most commonly in membranous interventricular septum over muscular

Question 13

When does formation of the aorta and pulmonary trunk occur?

Answer 13

5th week

Question 14

What is the process of formation of the aorta and pulmonary trunk?

Answer 14

aorticopulmonary septum divides the truncus arteriosus and bulbus cordis into aorta and pulmonary trunk.

aorticopulmonary segment spirals and splits into 2, causing aorta to curve behind pulmonary trunk.

Question 15

How are the mitral and tricuspid valves formed?

Answer 15

valves, cusps, papillary muscle and chordae tendonae form from ventricular wall. mitral has 2 cusps and tricuspid has 3

Question 16

How are the semilunar valves formed?

Answer 16

the sun-endocardial tissue endocardium grows, then folds to form a valve.

Question 17

Why does the foramen ovale exist?

Answer 17

heart functions before lungs in a foetus, as a circulatory system is needed to transport nutrients around body. no gas exchange occurs, so blood goes directly from right to left atrium.

Question 18

What generates impulses in the primitive atrium before nodes are formed? when are nodes formed?

Answer 18

myocytes. they are early pacemakers of the heart.

5th week is when SA and AV are formed

Question 19

How is the SA node developed?

Answer 19

from purkinje cells in the high right atrium, near entrance of superior vena cava

Question 20

What are the AV node and bundle of his developed from?

Answer 20

from the atrioventricular canal and sinus venosus.

Question 21

How and when is the heart tube formed?

Answer 21

day 20, embryo folds and 2 endothelial tubes fuse to form the primative heart tube. formed from splanchnic mesoderm.

Question 22

What are endocardial cushions called after they’ve fused? what do these go on to form?

Answer 22

septum intermedium. forms mitral and tricuspid valves and chordae tendonae come off these calves.

Question 23

What does the bulbus cordis and primitive ventricle form?

Answer 23

bulbus cordis forms right ventricle and primitive ventricle forms left ventricle. this is after formation of the muscular and membranous portions of the interventricular septum