1.3 Heart Development

Question 1

When are cardiac tissue cells defines?

Answer 1

During gastrulation cells of the primary heart field are specified

Question 2

What happens to the primary heart field during development?

Answer 2

Divides into first and second heart fields (based on times of cell differentiation)

Question 3

What structures develop from the first heart field?

Answer 3

L and R ventricles

Question 4

What structures develop from the second heart field?

Answer 4

R ventricle and Outflow tract

Question 5

How is the primitive heart tube formed?

Answer 5

Precursor cells from FHF differentiate
Two sides of heart zip together to form heart tube

Question 6

How does the straight heart tube form a four chambered heart?

Answer 6

Early looping - ventricle pushed down, atrium pushed up to form loop

Late looping - atrium pushed to top, ventricle pushed to bottom

Atrium divided into two (L and R), wedging

Ventricle divided into two (L and R), septation

Question 7

What is the alignment of atria and ventricles dependent on?

Answer 7

Dependent upon formation of endocardial cushions
Fuse to define left and right AV canals

Question 8

What are endocardial cushions made from?

Answer 8

Made from matrix jelly

Become populated by mesenchymal cells derived from endocardium

Question 9

What do the endocardial cushions give rise to in the developing heart?

Answer 9

Give rise to heart valves

Question 10

What is responsible for the division between left and right atria?

Answer 10

Septum primum grows down to divide L and R

Septum secundum grows down immediately adjacent

Question 11

Why is ostium primum important?

Answer 11

Initially allows communication between the two atria

Question 12

What is ostium secundum and when does it form?

Answer 12

Second ‘hole’ which forms after ostium primum closes

Allows continued communication between the two atria

Question 13

What is the difference between septum primum and septum secundum?

Answer 13

Septum primum is formed first

Septum secundum doesn’t grow down to reach and fuse with the AV cushion

Question 14

How are the ventricles separated?

Answer 14

Septated by the growth of muscular septum with mesenchymal cap (cap forced into contact with AV tissue and sill fuse)

Question 15

What is the final event in heart development?

Answer 15

Septation of OFT into aortic and pulmonary trunks to create dual circulation

Question 16

What causes the septation of the OFT?

Answer 16

OFT endocardial cushions that develop in same way as AV canal but neural crest cells responsible for OFT into aortic and pulmonary trunk

Question 17

How many aortic arches are there, and how many remain throughout development?

Answer 17

6

Aortic arches 1,2,5 do not fully form so are lost

Question 18

What does the 3rd aortic arch give rise to?

Answer 18

Left and right carotid arteries

Question 19

What does the 4th aortic arch give rise to?

Answer 19

Aorta
Right subclavian artery

Question 20

What does the 6th aortic arch give rise to?

Answer 20

Left and right pulmonary arteries
Ductus arteriosus

Question 21

Why does the foetus develop shunts?

Answer 21

Organs require some blood for development but still fragile so too much blood is harmful

Question 22

Name the major shunts and openings to restrict blood flow to the liver and lungs.

Answer 22

Ductus venosus
Ductus arteriosus
Foramen ovale (Ostium secundum)

Question 23

What is the Ductus Venosus?

Answer 23

Blood vessel which connects umbilical vein to the inferior vena cava

Question 24

What is the Ductus Arteriosus?

Answer 24

Blood vessel connecting the pulmonary trunk to descending aorta

Question 25

What is the Foramen Ovale?

Answer 25

Opening that connects Right to Left Atrium