B4.046 Prework 1: Early Heart Development

Question 1

which germ layer is the cardio system derived from?

Answer 1

lateral place (splanchnic) mesoderm

Question 2

1st trimester heart development overview

Answer 2

day 15-19: cardiac precursor fields
day 21-22: heart tube formation
day 28: cardiac looping
day 63: chamber septation, valve & outflow formation complete

Question 3

what do the first/second heart fields contain?

Answer 3

multipotent progenitor cells that can produce all of the major cell types of the heart and blood vessels

Question 4

major cell types of the heart and blood vessels

Answer 4

endothelium/endocardium
myocardium
smooth muscle cells

Question 5

how are heart fields differentiated?

Answer 5

expression of distinct gene sets

Question 6

what is derived from the first heart field

Answer 6

left ventricle

Question 7

what is derived from the second heart field

Answer 7

outflow tract, right ventricle, most of the atria

Question 8

beating tube

Answer 8

day 22

Question 9

heart tube loops to the right and begins to form chambers

Answer 9

day 28

Question 10

what are neural crest derived cells?

Answer 10

from the neural tube

Question 11

what do neural crest derived cells contribute to

Answer 11

1. conotruncal cushions that partition the outflow tract
2. endocardial cushions (form future atrioventricular canal)
3. aortic arches

Question 12

4 chambered heart arises after further septation

Answer 12

day 50

Question 13

valve and outflow tract formation is complete

Answer 13

day 63

Question 14

what is outflow tract formation?

Answer 14

aorta and pulmonary artery separation from respective ventricles

Question 15

BMPs 2 & 4

Answer 15

secreted by endoderm and LPM in anterior embryo

upregulate FGF8

Question 16

Wnt inhibitors

Answer 16

secreted by endoderm in anterior embryo

block Wnts that inhibit heart development, thus PROMOTE heart development

Question 17

NKX-2.5

Answer 17

induced by BMPs and Wnt inhibitors

induces heart formation from splanchnic mesoderm

Question 18

FGF8

Answer 18

leads to expression of cardio specific proteins

Question 19

what are blood islands

Answer 19

angioblasts and hematopoietic cells

Question 20

how does cranial/cephalic folding and rapid growth of the brain impact the heart?

Answer 20

1. rotates cardiogenic area
2. moves it ventrally and caudally
3. re-orients heart tube and pericardial cavity

Question 21

what are the 4 layers of the cardiac tube?

Answer 21

from inside to outside

1. endocardium (primitive endothelium)
2. cardiac jelly (ECM)
3. myocardium (heart muscle)
4. epicardium (visceral pericardium)

Question 22

what is the epicardium derived from?

Answer 22

mesothelial cells on the surface of the septum transversum form the pro-epicardial cells in the caudal heart tube and migrate over the myocardium

Question 23

regions of heart tube from cranial to caudal

Answer 23

1. single aortic sac (blood outflow, truncus arteriosus)
2. single bulbus cordis
3. single ventricle
4. single atrium
5. right and left sinus venosus (blood intake)

Question 24

how are segments of the heart tube differentiated?

Answer 24

lower levels of retinoic acid near cranial heart tube specifies outflow tract and ventricle segments
higher levels of retinoic acid near caudal heart tube specify venous intake segments (atrium and sinus venosus)

Question 25

what happens with abnormal levels of retinoic acid?

Answer 25

adverse effect specification, anterio-posterior patterning of the heart tube, and the cardiac neural crest cell populations

Question 26

ventricle movement during looping

Answer 26

ventral, caudal, and to the right on day 23

Question 27

atrium movement during looping

Answer 27

dorsal, cranial, and to the left on day 24

Question 28

when does blood start to circulate?

Answer 28

day 24-25

R and L ventricles and atria also start to form around this time