Session 3 Flashcards
In which week of embryonic development does folding occur?
4th week
The cardiogenic field is an area of what type of embryonic tissue?
Mesoderm
What happens in the cardiogenic field to begin the development of the heart?
The beginnings of differentiation start and blood islands appear
What are blood islands?
Areas of differentiating cells in the cardiogenic field that have the capacity to make blood cells/vessels/heart muscle
How is the primitive heart tube formed?
2 endocardial tubes with blood islands exist in the embryo before it folds.
As the embryo folds, the tubes meet at the midline and fuse to from a single primitive heart tube
What are some possible causes of congenital heart defects?
Genetic
Exposure to chemicals/drugs/infectious agents
Describe the basic structure of the primitive heart tube
Effectively a modified blood vessel with an inlet and outlet
Describe the different parts of the primitive heart tube from inlet to outlet
Sinus venosus Atrium Ventricle Bulbus cordis Truncus arteriosus Aortic roots
What does the sinus venosus consist of?
4 inlet tubes
How does blood flow in the primitive heart tube?
Straight from inlet to outlet with nothing to regulate the flow - simple contractile tube
When does cardiac looping take place? What is cardiac looping? What is its function?
When the primitive heart tube elongates and runs out of room
The twisting and folding up of the primitive heart tube
Places the inflow and outflow of the heart in the correct orientation
What part of the primitive heart tube does the right atrium develop form?
Most of the primitive atrium and a small part of the sinus venosus
What part of the primitive heart tube does the left atrium develop from?
A small portion of the primitive atrium and absorbs proximal parts of the pulmonary veins
Which atrium has smooth walls? Why?
Left atrium
Absorbs parts of the proximal pulmonary veins
Do the lungs work in a foetus?
No - no gas exchange can take place
Where does oxygenation and removal of carbon dioxide from the blood take place in a foetus?
At the placenta
What structures are required to maintain fetal life with regards to the blood circulation in a foetus?
Shunts
Name three shunts found in a foetus
Foramen ovale
Ductus arteriosus
Ductus venosus
Blood enters the foetus through which vessel?
The umbilical vein
What is the first shunt encountered by the blood entering the umbilical vein?
Ductus venosus
Describe what happens to the blood at the ductus venosus. What is the purpose of this?
It is shunted around the liver to the inferior vena cava
The liver is highly metabolically active in fetal life so could easily consume all of the oxygenated blood
What is the function of the foramen ovale?
Shunts blood from the right atrium across to the left atrium to be pumped around the body