Embryology Of The Heart

Question 1

Why bother with embryology?

Answer 1

Insight into post natal anatomy

Understand congenital heart disease

Increasing hope that adult disease could be treated by invoking embryonic processes

Factors you are exposed to even before you are born may influence if you get heart disease

Question 2

What is gastrulation?

Answer 2

Gastrulation is the process during embryonic development that changes the embryo from a blastula with a single layer of cells to a gastrula containing 3 layers - ectoderm, mesoderm and endoderm.

Question 3

What does the ectoderm form?

Answer 3

Skin, nervous system, neural crest

Question 4

What does the mesoderm form?

Answer 4

All types of muscle, most of the cardiovascular system, kidney, blood, bone, cartilage

Question 5

What does the endoderm form?

Answer 5

G-I tract and the organs off it e.g liver, pancreases and the endocrine organs.

Question 6

What embryonic cells form the cardiovascular system?

Answer 6

Mostly formed of the mesoderm, with a little contribution from cardiac neural crest cells which form from the ectoderm.

Question 7

What are the heart fields and when do they form?

Answer 7

The heart fields are made up of the cells that will develop to form the heart, (its precursors).

You have 2 heart fields, one will form the left ventricle, the 2nd will form the outflow tract, right ventricle and atria.

The two heart fields fuse along with the cardiac neural crest - day 21.

First formation of hart field at day 15.

Question 8

See notes for some cardiac transcriptional factors.

Answer 8

E.g NKx2.5
GATA
Hand
Etc

Question 9

What are the 3 stages in order of cardiac formation?

Answer 9

Formation of the heart fields and then:

Formation of the primitive heart tube

Cardiac looping

Cardiac septation

Question 10

Describe the formation of the primitive heart tube…

Answer 10

During the third week of development the heart is formed from a horseshoe shaped region called the cardiogenic region.

By day 19 two endocardial tubes form. These two tubes will fuse to form a single primitive heart tube…

Question 11

Describe the events Durig cardiac looping…

Answer 11

The bulb is cordis moves inferiority, anteriorly and to the embryos right.

The primitive ventricle moves to the embryos left side

The primitive atrium and sinus venosus moves superiorly and posteriorly.

Question 12

Describe the events of cardiac septation

Answer 12

1. The atrium and ventricle are connected by an internal opening known as the atrioventricular canal. (Whole between the only 2 chambers)
2. Blood will first enter the atrium pass through the atrioventricular canal into the ventricle and finally out through the turn us ateriosus
3. Masses of tissue called endocardial cushions (inferior and superior) grow from the side of the AV canal. They cause the formation of 2 separate openings now known as the left and right atrioventricular canals.

Question 13

How many pregnancies don’t result in a live birth?

Answer 13

1/8