development of the heart

Question 1

where does the heart develop from?

Answer 1

the splanchnic of the mesoderm

Question 2

when does the heart tube form?

Answer 2

3 weeks

Question 3

what are the different parts of the primitive heart?

Answer 3

at day 22 the primative heart forms
arterial outflow from top
truncus arteriosus
primitive ventricle
primitive atria
sinus venousus
venous inflow from bottom

Question 4

what happens during heart folding?

Answer 4

1. the primitive atria moves posteriorsuperiorly relative to the primative ventricle
2. the pericardium folds with and around the primative heart

Question 5

what are the 2 layers of the pericardium?

Answer 5

serous portion:
visceral = in contact with heart
parietal = more superior
pericardial fluid between these 2 layers

fibrous portion:
more superior than the parietal part

Question 6

what are the 2 sinuses which form in heart development?

Answer 6

tranverse pericardial sinus = seperates the inflow and outflow tracts (finger thing)
oblique sinus = space within pericardial cavity behind the heart

Question 7

what does the adult atria developed from?

Answer 7

the primative atria AND sinus venosus
the atria has 2 parts, rough and smooth
rough = primative atria
smooth = sinus venosus (this results in formation of SAN)

Question 8

how many aoritc arches are present in heart development?

Answer 8

5 aortic arches:
1, 2, 3, 4 + 6 (5 doesnt develop)

Question 9

which aortic arches gives rise to the adult aortic arch?

Answer 9

the left 4th aortic arch

Question 10

which aortic arches gives rise to the right subclavian artery?

Answer 10

the right 4th aortic arch

Question 11

which aortic arch gives rise to the common carotid arteries?

Answer 11

right 3rd arch + ventral aortae

Question 12

which aortic arches gives rise to the L + R pulmonary arches?

Answer 12

develop from the L + R 6th aortic arch respectively

Question 13

what allows the ductus arteriosus to form?

Answer 13

the left 6th aortic arch doesnt degenerate so the left pulmonary artery can drain into the aorta (important shunting mechnaism in heart)

Question 14

how do we septate between primative atria and ventricle?

Answer 14

septation of atrioventricular canal:
1. endocardial cushions develop from doral and ventral walls of atrioventricular canal
2. endocardial cushions grow and meet = seperate atrioventricular canal into left and right
3. must fuse with interventricular and interatrial septums to allow for proper septation of the heart

Question 15

how do we form an interatrial septum?

Answer 15

1. septum primum grows down towards the endocardial cushions - leaves a hole between the septum primum and endocardial cushions which forms ostium primum
2. ostium primum closes but a new hole forms in the septum primum = ostium secundum
3. septum secundum grows down towards endocardial cushions
4. results in formation of foramen ovale which acts as a valve to allow for R-L shunting

Question 16

how do we form an interventricular septum?

Answer 16

1. muscular portion grows upwards from muscular ventricle wall
2. membranous portion grows down from endocardial cushions and fuses with muscular portion

Question 17

how do we form an outflow septum (septation of truncus arteriosus)?

Answer 17

1. ridges of tissue form in a helical form and grow down towards endocardial cushions
2. spiral septum completes seperating the outflow tract into pulmonary artery and aorta

Question 18

When does the primitive heart fold?

Answer 18

4th week