Development of Heart Flashcards
How is the heart slightly twisted in situ?
Would predominantly see right side as left side predominantly towards posterior
When does formation of heart begin?
Week 3
When is first contraction of heart?
Day 22
What are the 3 layers of the heart?
Epicardium Myocardium Endocardium
What is the epicardium? What is it derived from?

Protective outer layer of heat BUT visceral (inner) layer of pericardium (heart cavity) Derived from visceral mesoderm
What is the myocardium? What is it derived from?

Middle –> goes on to form heart muscles Derived from the visceral mesoderm overlying the heart tube
What is the endocardium? What is it derived from?

Inner lining of heart Derived from the heart tube
What is vasculogenesis?
Creating blood vessels from scratch
What is angioblast?
The embryonic tissue from which blood vessels arise
How are angioblasts formed?
The endoderm induces some cells of the overlying mesoderm to differentiate into angioblasts

What do angioblasts then differentiate into?
Endothelial cells which form endocardial tubes with overlying myocardial cells

What does the lateral plate mesoderm get split into?
- Parietal layer
- Inner splanchnic (visceral) layer
What does the splanchnic (visceral) layer go on to form?
The endocardial tubes and myocardial cells

How is the primitive heart tube formed?
Endocardial tubes fuse during lateral folding to form the primitive heart tube

Why does lateral folding occur?
Due to the weight of the amniotic sac
Where is the endocardial (primitive heart) tube in relation to the gut tube?
Ventral to the gut tube

What does the visceral mesoderm surrounding the primitive heart tube differentiate to form?
The myocardium (heart muscle)

What does the myocardium secrete?
A thick layer of extracellular matrix (cardiac jelly)
What brings the developing heart tube into the thorax?
Craniocaudal folding (head and tail end come into closer proximity)
Describe the 3 layers of the resultant heart tube
- Endocardium
- Forming the internal endothelial lining of heart
- Endocardial tube surrounded by cardiac jelly - Myocardium
- Forms muscular wall (myocytes) - Epicardium
- Covering the outside of the heart tube
What is outer layer of heart tube (epicardium) responsible for?
Formation of the coronary arteries
What is purpose of cardiac jelly?
Is a gelatinous connective tissue separating the myocardium and heart tube endocardium
At the 4th week, what is responsible for the inflow of blood to the primitive heart?
The sinus venosus. Right and left sinus horns empty into primitive atrium.

What is the sinus venosus?
At caudal end of the developing heart tube. Largely degerates by week 5. Splits into left and right horn.









