CVS-embryology

Question 1

What day does the formation of the heart begin?

Answer 1

Week 3/ 18 days

Question 2

When is the first heartbeat heard?

Answer 2

Week 4 /day 22

Question 3

where do endocardial heart tubes form?

Answer 3

on each side of the heart tube

Question 4

what does folding of heart tubes do?

Answer 4

brings them together-they fuse into a single heart tube

Question 5

what are the 5 regions of the heart tube?

Answer 5

• sinus venosus (venous flow)
• primitive atrium
• primitive ventricle
• bulbus cordis
• truncus arteriosus (aterial flow)

Question 6

which structures does the truncus arteriosus become?

Answer 6

ascending aorta

pulmonary trunk

Question 7

what does the bulbus cordis become?

Answer 7

right ventricle

Question 8

what does the primitive ventricle become?

Answer 8

left ventricle

Question 9

which structures does the primitive atrium become?

Answer 9

RA , anterior wall LA, right auricle, left auricle

Question 10

which structures does the sinus venosus become?

Answer 10

posterior wall RA, coronary sinus, SA node

Question 11

where does the heart develop from?

Answer 11

the mesoderm

Question 12

describe how the heart folds

Answer 12

1-heart tube folds + regions grow → ventricle and bulbus cordis grow most

2-ventricle grows most → causes deepening of bulboventricular groove and appearance of atrioventricular groove

3-Folding of heart tube gives shape of adult heart

4-Now needs to be partitioned internally to separate single tube into 4 chambers

Question 13

in what week on development do the endocardial cushions form?

Answer 13

week 5

Question 14

describe the events which occur in week 5-7 of development

Answer 14

1-formation of endocardial cushions

2-partitioning of atrium

3-partitioning of ventricle

4-partitioning of bulbus cordis and truncus ateriorsus

Question 15

what does the formation of endocardial cushions do?

Answer 15

-splits atrium from ventricle

Question 16

which structures do the endocardial cushions eventually become?

Answer 16

AV valves

Question 17

what does the partitioning of the atrium do?

Answer 17

splits single atrium into left and right

Question 18

what does the partitioning of the ventricle do?

Answer 18

splits single ventricle into left and right

Question 19

what does the partitioning of the bulbus cordis and truncus arteriosus do?

Answer 19

split into aorta and pulmonary trunk

Question 20

outline the steps in the partitioning of the atria.

Answer 20

1. septum primum forms, with a hole inside = foramen primum
2. As foramen primum is closing, apoptosis occurs further up septum primum
3. Now foramen primum is closed, and foramen secundum is formed as a result of apoptosis
4. septum secundum forms in RA, with another hole – foramen ovale → Blood flows between the two atria through these holes

Question 21

in new borns what happens to the septum primum and secundum?

Answer 21

forced together, due to increased pressure in atria = holes close

Question 22

what is the name if the septum which splits aorta from pulmonary trunk?

Answer 22

aorticopulmonary septum

Question 23

why is there a 180 degree rotation of the truncus arteriosus?

Answer 23

so that the pulmonary trunk sits anteriorly and the aorta, posteriorly

Question 24

what is the role of the sinus venosus?

Answer 24

directs venous inflow into heart – has right and left horn

Question 25

what does the left horn of sinus venosus become?

Answer 25

Regresses to become the coronary sinus

Question 26

what does the right horn of sinus venosus become?

Answer 26

Enlarges to become part of the SVC and right atrium

Question 27

name the 3 vascular shunts in foetal circulation

Answer 27

• Ductus venosus
• Foramen ovale
• Ductus arteriosus

Question 28

what does the ductus venosus bypass?

Answer 28

liver

Question 29

what does the foramem ovale bypass?

Answer 29

lungs (blood travels from RA to LA)

Question 30

what does the ductus arteriosus bypass?

Answer 30

lungs (blood travels from pulmonary trunk to aorta)

Question 31

what is different about foetal Hb?

Answer 31

• Has much higher affinity for O2 binding than adult haemoglobin
• Becomes saturated at lower pO2

(due to o2 availability being much lower in foetus than adult)

Question 32

at which age does foetal Hb change to adult?

Answer 32

within 6 months as site of haematopoiesis changes

Question 33

what causes the foramen ovale to close?

Answer 33

• increased blood flow into LA from pulmonary veins raises pressure in LA
• causes flap to close

Question 34

when should the foramen ovale fuse?

Answer 34

~3 months

Question 35

what is the remnant of foramen ovale called in adults?

Answer 35

fossa ovalis

Question 36

how is the ductus arteriosus kept open in a foetus?

Answer 36

• prostaglandins (PGE2 and PGE1) secreted by placenta

- this inhibits vasoconstriction of ductus arteriosus and keeps it patent (open/unobstructed) as a shunt

Question 37

what causes the ductus arteriosus to close after birth?

Answer 37

• PGE2 and PGE1 levels drop

- ductus arteriosus vasoconstricts until lumen is closed

Question 38

what is the remnant of ductus arteriosus in adults?

Answer 38

ligamentum arteriosum

Question 39

how does the ductus venosus close after birth?

Answer 39

• PGE2 and PGE1 levels drop
• sphincter contracts around DV = forces blood into liver sinusoids
• Empty DV closes/fuses

Question 40

what is the remnant of ductus venosus in adults?

Answer 40

ligamentum venosum

–>in posterior view LV is between L and R lobes

Question 41

what is an example of an atrial septal defect (ASDs)?

Answer 41

-patent foramen ovale
(hole in heart)
–>most common ASD

Question 42

what are examples of ventricular septal defects (VSDs)?

Answer 42

• partial absence of ventricular septum
• > reasonably common
• complete absence of septum
• > very rare