Embryology Of The Heart

Question 1

What is an early phase of embryonic development and when does it occur?

Answer 1

Gastrulation

3rd week

Question 2

What happens during gastrulation?

Answer 2

During this phase the embryoblast develops into a trilaminar (three layered structure) called gastrula and forms three germ layers

Question 3

What are the 3 germ layers called?

Answer 3

Ectoderm
Mesoderm
Endoderm

Question 4

What does the ectoderm form?

Answer 4

Outer layer - structures in contact with outside of the body
Skin, NS (peripheral & central), cardiac crest cells

(Pituitary, mammary and sweat glands)

Question 5

What does the mesoderm form?

Answer 5

All muscle, cardiovascular system, cartilage and bone, urogenitial system

Question 6

What does endoderm form?

Answer 6

Liver, pancreas, endocrine organs, GI epithelial lining

Question 7

When does the folding of the primitive heart tube occur & what happens each day?

Answer 7

Pre day 19 - heart is formed by cells that form a ‘horse shoe’ shape, called the cardiogenic region

Day 19 - 2 endocardial tubes form

Day 20/21 - the tubes fuse to form the primitive heart tube

Question 8

What are the 5 parts of the heart tube?

Answer 8

Trunchus arteriosis
Bulbus cordis
Primitive ventricle
Primitive atrium
Sinus venosus

Question 9

What happens by day 22?

Answer 9

The heart begins to beat

Question 10

What happens by day 23?

Answer 10

The heart tube begins to fold

Question 11

Which way does each section fold?

Answer 11

Bulbus cordis - folds inferiorly, anteriorly & right

Primitive ventricle - shifts left

Primitive atrium & sinus venosus - more superiorly & posteriorly

Question 12

What does the trunchus arteriosis form?

Answer 12

Aorta & aortic arches

Question 13

What does the bulbus cordis form?

Answer 13

Proximal aorta and pulmonary trunk

Question 14

What does the primitive ventricle form?

Answer 14

Left ventricle

Question 15

What does the primitive atrium form?

Answer 15

All of left atrium, part of right atrium, left and right auricles

Question 16

What does the sinus venosus form?

Answer 16

Part of right atrium, vena cava, coronary sinus

Question 17

What is the asymmetry in the heart due to?

Answer 17

Cilia wafts molecules R —> L (why muscle wall in L is thicker)

Adaptation to increase molecule conc on left

Question 18

What happens in septation?

Answer 18

Superior & inferior endocardial cushions grow and meet at central atrioventricular canal

Question 19

Where does the superior& inferior grow from?

Answer 19

Superior - grows from bottom up

Inferior - grows from top down

Question 20

What does the superior continue up to do?

Answer 20

Divide Left and right atria (interatrial septum)

Question 21

What is the embryologist deficit (gap) in the atria?

Answer 21

Foramen ovale (allows blood to flow freely through left and right atria)

Question 22

What happens at birth to the foreman ovale?

Answer 22

Closed off and becomes fossa ovale

Question 23

What does the inferior continue down to divide?

Answer 23

Separate the left & right ventricle, interventricular septum

Has an upper and lower membranous part

Question 24

What do the aortic arches develop/branch off?

When does it occur?

Answer 24

Trunchus arteriosis

27 days to 7 weeks

Question 25

What does the Trunchus arteriosis continue upwards to form?

Answer 25

Aortic sac

Question 26

How many aortic arches are there?

Answer 26

6

Question 27

What does the first branch form?

Answer 27

Maxillary artery

Question 28

What does the second branch form?

Answer 28

Hyoidal

& stapedial

Question 29

What does the third branch form?

Answer 29

Common carotids

Proximal portion of internal carotid artery

Question 30

What does the fourth branch form?

Answer 30

Left - aortic arch

Right - Right subclavian branches

Question 31

What does the fifth branch form?

Answer 31

Nothing, regresses

Question 32

What does the 6th branch form?

Answer 32

Right - pulmonary trunk

Left - ductus arteriosis