Lecture 19: Heart embryology

Question 1

How does the heart tube develop?

Answer 1

from the fusion of the paired heart tubes that arise from the angioblastic cords

Question 2

path of blood flow through single tube heart, from cranial to caudal

Answer 2

sinus venosus–>sinoatrial valve –> primitive atrium,–>atrioventricular canal –> primitive ventricle, –>bulbus cordis, –>truncus arteriosis, –> aortic sac,

Question 3

What is cardiogenic mesoderm

Answer 3

Mesoderm that migrated cranial to the pre-chordal plate during formation of the primitive groove

Question 4

position of angioblastic cords

Answer 4

directly adjacent to the intra-embryonic coelem

Question 5

fate of angioblastic cords

Answer 5

eventually form paired heart tubes/aorta, which fuse to form single dorsal aorta and single tube heart

Question 6

initial position of cardiogenic mesoderm

Answer 6

Cranial to pre-chordal plate, near septum transversum and head of horseshoe part of intra-embryonic coelem. During cranial caudal folding migrates towards the chest, along with those associated structures.

Question 7

fate of blood islands

Answer 7

form network of arteries and veins within the yolk sac connected to rest of circulation through the vitelline arteries and veins

Question 8

umbilical artery and vein

Answer 8

connect the chrionic sac/maternal circulation to dorsal aorta (umbilical artery) and sinus venosus (umbilical vein)

Question 9

What does the fetal circulation lack, notably

Answer 9

circulation through the lungs

Question 10

What causes the heart to fold

Answer 10

1. more dominent proliferation on one side 2. aided by cranial caudal folding

Question 11

function of fusing AV endocardial cushions

Answer 11

Creates a left and right side of the heart/ left and right AV canals, separates atria from ventricles, fused endocardial cushion plays a role in the formation of mitral valve and tricuspid valve

Question 12

What forms during heart folding

Answer 12

fused endocardial cushion, primordial IV septum, septum primus

Question 13

How does Interventricular (IV) septum form

Answer 13

myocardium grows from the the bottom wall between the two ventricles towards the indocardial cushion, while a membranous septum grows down from the endocardial cushion and joins the muscular outgrowth.

Question 14

ventriculoseptal defect

Answer 14

the most common cardiac defect, found in the membranous septum tissue between ventricles. Most of the time will close naturally

Question 15

functions of papillary muscle

Answer 15

holds AV valves down, stop them from pro-lapsing (folding back into the atrias) when the ventricles contract.

Question 16

septum primums

Answer 16

grows down from wall of atrium, towards endocardial tissue. Eventually meets endocardial tissue. Has foramen secundum permanently in it. After formation of foramen secundum top part of septum primum degenerates

Question 17

foramen primum

Answer 17

hole that forms between the septum primum and endocardial cushion to allow blood to flow from right atrium to left atrium, just by virtue of the septum primum not reaching all the way down to the cushion. will eventually close during development/growth of septum

Question 18

foramen secundum

Answer 18

Formed from little perforations in the septum primum that coalesce to form a hole further up in the septum from the foramen primum. this one remains open. After formation top part of foramen primum degenerates

Question 19

septum secundum

Answer 19

the second septum grows more anterior to the septum down from the ceiling of the atrium towards the endocardial tissue, stops short of the endocardial cushion, over-laps slightly from septum primum extending up from endocardial cushion

Question 20

Oval foramen

Answer 20

hole that is between the septum primum and septum secundum, which could overlap but are not connected to each other. Between left and right atria.

Question 21

what makes up the valve of the oval foramen

Answer 21

the septum primum and septum secundum. the opening is in secundum, flap that covers it up is primum (what moves in rxn to blood pressure). these eventually fuse after birth to create inter-atrial septum. some people will still have holes in their heart

Question 22

Foramen Ovale

Answer 22

blood bypasses the lung, acts as a shunt between the right and left atria

Question 23

What causes the foramen ovale to close

Answer 23

the left atrial pressure increases, pulmonary vascular resistance decreases (loss of pulmonary fluid after birth)

Question 24

left vs. right ventricular outflow tracts

Answer 24

left ventricular outflow –> aorta

right ventricular outflow –> pulmonary artery

Question 25

Where do conotruncal ridges form

Answer 25

two ridges in the truncus arteriosis and the bulbus cordis, one from each opposite sides of the vessel wall, grow towards each other to meet in the middle while also spiralling around each other 180 degrees

Question 26

What do the conotruncal ridges fuse to form

Answer 26

the aorticopulmonary septum between primordial aorta and pulmonary artery. The aorticopulmonary septum joins with the interventricular septum

Question 27

how do the pulmonary and aorta position with respect to each other

Answer 27

they twist 180 degrees as they grow towards each other. This causes the mature anatomy of the pulmonary artery from being anterior at the root, then posterior to the arch, and the anterior to the descending aorta.

Question 28

semilunar valves

Answer 28

found in aorta and pulmonary artery

Question 29

formation of semilunar valves

Answer 29

created from 3 subendocardial swellings, which were remodeled to form three thin walled cusps

Question 30

the atrioventricular (AV) valves

Answer 30

The mitral and tricuspid valves

Question 31

formation of AV valves

Answer 31

develop from proliferation of tissue around endocardial cushion/AV canals

Question 32

what does the dorsal aorta rise from

Answer 32

a pair of tubes formed from angioblastic cords, a pair of dorsal aorta are formed, there would be two visible in the cross section

Question 33

What does the dorsal aorta do

Answer 33

Connects to the aortic arches, which arise from the aortic sac

Question 34

Where do the aortic arches come from?

Answer 34

They come from the arteries associated with the pharyngeal arches. Six aortic arches develop, each one paired to it's own pharyngeal arch. Each arch has left and right side that arises from central aortic sac and ends in either the left or right dorsal aorta.

Question 35

what does the 3. aortic arches develop into mature structures

Answer 35

r. and l. 3 --> r. and l. common carotid artery

Question 36

what does 6 aortic arch develop into

Answer 36

the l. 6 aortic arch gives rise to the left pulmonary artery and ductus arteriosus, and the right pulmonary artery comes from the r. 6 aortic arch

Question 37

what does the 4 aortic arch develop into

Answer 37

l. 4th --> significant part of the aortic arch, | r. 4th --> prox r. subclavian artery

Question 38

what are the cardiac veins

Answer 38

vitelline veins from yolk sac (low O2) umbilical veins (high O2) common cardinal veins from embryo body (low O2)

Question 39

where do the cardiac veins dump into

Answer 39

the sinus venosus

Question 40

Does everyone have the same veinous set-up

Answer 40

no, highly variable vessel connection pattern between individuals

Question 41

how many umbilical veins are there initially

Answer 41

two, but only the left one persists, right one disappears

Question 42

how does blood flow from the placenta

Answer 42

oxygenated blood flows from the placenta through the umbilical vein, then through the ductus venosus in the liver to bypass passing through the liver before the oxygenated blood goes to the heart

Question 43

Tetralogy of fallot four factors

Answer 43

pulmonary stenosis, ventricular septal defect, overriding aorta, right ventricular hypertrophy, caused by unequal partitioning of the truncus arteriosis by the conotruncal ridges

Question 44

tetralogy of fallot, why pulmonary stenosis?

Answer 44

because of unequal partitioning of the truncus arteriosis

Question 45

tetralogy of fallot, why ventricular septal defect

Answer 45

the aortic wall did not join up with the interventricular septum

Question 46

tetralogy of fallot, why right ventricular hypertrophy

Answer 46

the right ventrical needs to pump against a lot of resistance (the stenosis of R. pulmonary artery)