Lecture 5 (Heart Development)

Question 1

What organ is the first to begin functioning?

Answer 1

the heart

Question 2

By what day are the two heart tubes formed?

Answer 2

Day 20

Question 3

What happens on day 21 with the endocardial tubes?

Answer 3

they fuse into the primitive heart tube

Question 4

When does the heart begin to beat?

Answer 4

day 22 (after fushion of heart tubes)

Question 5

What four major events happen to the primary heart tube from wks 4-8?

Answer 5

• looping/folding
• remodeling
• realignment
• septation

Question 6

What process brings the two endocardial tubes together so they can fuse?

Answer 6

lateral body folding

Question 7

On day 23, the heart begins to:

Answer 7

loop

Question 8

Heart looping is complete by:

Answer 8

Day 28

Question 9

The septum primum begins forming when the heart looping is complete on day:

Answer 9

28

Question 10

What endocardial tissues form during week 5?

Answer 10

cushions

Question 11

Atrioventricular endocardial cushions fuse to form __________ around day _____.

Answer 11

atrioventricular septum

day 42

Question 12

In week 7, what structure is formed by the septum primum and Secundum?

Answer 12

forman ovale

Question 13

What happens to the outflow tract of the heart around week 8?

Answer 13

they become fully septated thanks to fusion of outflow tract cushions

Question 14

ventricular septation is completed by:

Answer 14

joining of outflow tract, atrioventricular, and muscular interventricular septa

Question 15

Where is the cardiogenic field established?

Answer 15

cranial to neural plate

Question 16

What forms in the visceral layer of lateral plate mesoderm cranial to developing brain then coalesce?

Answer 16

blood islands

Question 17

What primitive structure forms as blood islands coalesce in the cardiogenic field?

Answer 17

primitive heart tube - horseshoe-shaped endothelial tube

Question 18

The cardiogenic field becomes established in week:

Answer 18

3

Question 19

What master regulator is responsible for heart development?

Answer 19

NKX-2.5

Question 20

What morphogens are responsible for expression of NKX-2.5 in the cardiogenic field?

Answer 20

upregulation of BMPs

downregulation of WNTs

Question 21

How many cardiac fields form? What are they called?

Answer 21

2 - primary and secondary

Question 22

What else is occurring as the body folds to bring the heart tubes together?

Answer 22

midgut remodeling, vitelline duct is constricted, liver and lung buds form

Question 23

The caudal end of the heart tube is the ______ end

Answer 23

venous

Question 24

the cranial end of the primitive heart is the _______ end. What sprouts from here?

Answer 24

arterial.

vessels.

Question 25

The sprouted vessels of the cranial end of the heart become the:

Answer 25

aortic arches.

Question 26

Which signaling molecules are responsible for lopping and sidedness? What other signals do these repress?

Answer 26

NODAL and LEFTY2 -> PITX2 BMP and WNT are repressed

Question 27

NKX2.5 leads to the expression of which two signaling molecules?

Answer 27

HAND 1 and HAND2

Question 28

HAND1 expression leads to development of ->

Answer 28

left ventricle

Question 29

HAND2 expression leads to development of ->

Answer 29

right ventricle

Question 30

After looping, the heart is on the _____ side of the body.

Answer 30

left

Question 31

What is dextrocardia?

Answer 31

when the heart is on the right side of the body instead of the left due to an error in looping

Question 32

Which ways do the atrial and ventricular regions of the heart grow during looping?

Answer 32

``` atrial = up and left ventricular = down and right ```

Question 33

What days does heart looping occur?

Answer 33

22-24

Question 34

By day 24 what L and R structures have formed?

Answer 34

sinus horns

Question 35

What happens to the sinus horns by day 35?

Answer 35

R sinous horn has fused with the atrium L sinus horn has formed the coronary sinus and oblique vein of left atrium

Question 36

What is happening in the atria from days 27-37?

Answer 36

septal formation

Question 37

What has occurred btwn the atria and ventricles by day 33?

Answer 37

they have been separate by the usion of endocardial cushion

Question 38

By day 37, what separates the right and left atrium?

Answer 38

the septum primum and secundum

Question 39

What structure is formed by the septum primum and secundum?

Answer 39

the foramen ovale

Question 40

What is forming in the ventricules around the same time as the foramen ovale? day?

Answer 40

ventricular septum

Question 41

By what week have the atrioventricular valves formed? What do they form from?

Answer 41

7th week endocardial cushion

Question 42

Septation of the outflow tract of the heart is occurring around day:

Answer 42

35.

Question 43

Heart septation is complete by week:

Answer 43

8

Question 44

When do neural crest cells migrate to the heart?

Answer 44

3.5-4 weeks

Question 45

What is the most common type of heart defect? Where do most of them occur?

Answer 45

interventricular septal defects most occur in muscular portion of the septa, others occur in membranous portion

Question 46

How does transposition of the great vessels occur? What is considered the cause?

Answer 46

conotruncal cushions dividing the outflow tract fail to rotate 180 degree neural crest related abnormality

Question 47

What condition is characterized by four distinct cardiac abnormalities appearing together? What is the believed cause?

Answer 47

tetraology of fallot neural crest cells

Question 48

What is responsible for the transition to post natal blood flow?

Answer 48

pressure causing the foramen ovale to close

Question 49

Mutations in which gene cause ASDs and atrial conduction delays?

Answer 49

NKX2.5

Question 50

Mutations in what gene can cause Holt-Oram syndrome, preaxial limb defects w/ ASDs, and heart-hand syndromes?

Answer 50

TBX5

Question 51

How do blood vessels form?

Answer 51

vasculogenesis and angiogenesis

Question 52

What things form from vasculogenesis?

Answer 52

the heart and major vessels

Question 53

What things form through angiogenesis?

Answer 53

smaller vessels

Question 54

What molecules are necessary for vessel formation?

Answer 54

VEGFs

Question 55

Which aortic arch doesn't form?

Answer 55

5th

Question 56

Which aortic arches form first?

Answer 56

the most cranial form and differentiate as the more caudal ones form

Question 57

which aortic arches from major vessels? List all.

Answer 57

3rd -> carotid system 4th -> right: subclavian, left: arch of the aorta 6th -> pulmonary arteries and ductus arteriosus