Cardiovascular Flashcards
(23 cards)
Why is foetal circulation different to a child’s?
Lungs are not developed so pulmonary circulation causes high resistance and cannot deal with all the blood. INstead there are a series of shunts and nutrients and oxygen come from the placenta.
What is the umbilical cord comprised of? (and what are they called after birth)
One umbilical vein (with oxygenated blood) (becomes Ligamentum Teres)
2 umbilical arteries (become medial umbilical ligaments)
What happens to the blood after it leaves the placenta?
Travels in umbilical vein, bypassing the liver via the Ductus Venosus, joins venous blood and enters the right atrium
What happens to oxygenated blood entering the right atrium?
Passes through Foramen Ovale into L atrium and gets pumped into systemic circulation. Some blood enters right ventricle and leaves via the pulmonary artery but enters aorta through the Ductus Arteriosus (to bypass lungs)
What does the Ductus Arteriosus become?
Ligamentum Arteriosum
What does the Ductus Venosus become?
Ligamentum Venosum
What happens at birth?
Placental circulation stops, lungs expand and 3 shunts close
When does the circulatory system develop? Why is this a risk?
In weeks 3-7
Mother may be unaware of pregnancy so risk factors include rubella, thalodomide, alcohol, maternal diabetes
How does the embryo receive nutrition before the cardiovascular system is functional?
Nutrition is provided by the yolk sac and trophoblast
When does the heart start to beat?
At day 22
How are blood vessels formed?
Angiogenic clusters in yolk sac, chorion and connecting stalk
Cavities in clusters form blood vessels (outer cells form endothelium of vessel)
These channels extend into the embryo
What are the two atrial septums?
Septum primum and secundum (secondum like a curtain over the intra-atrial fenestration to form the foramen ovale flutter valve (blood only flows from R atrium to L)
What are the two layers of ventricular septum?
Muscular and membranous
What does the heart start of as? With what at each end?
A simple tube, anchored at the bottom by venous channels that lead into the atria and by arterial trunks (from bulbus cordis)
What happens when the heart tube grows?
The ventricle bends to the right of the midline (days 22-24) and then grows back to midline, expanding in length and covering the atria
What does the right ventricle communicate with?
Truncus arteriosus
How do the artio-ventricular septum form?
Endocardial growth from the walls, forms endocardial cushions that fuse
What splits the truncus arteriosus?
A spiralling septum that grows down from the bifurcation of the truncus arteriosus. Splits into pulmonary artery and aorta. Helps close the inter-ventricular septum
What are the 3 types of congenital heart defects?
Acyanotic, outflow obstruction and cyanotic
Give 3 examples of acyanotic heart defects
- Ventricular septal defect
- Persistent ductus arteriosus
- Atrial septal defect
Give 3 examples of outflow obstruction defects
- Pulmonary stenosis
- Aortic stenosis
- Coarctation of aorta
Give 2 examples of cyanotic heart defects
- Tetralogy of Fallot (Ventricular septal defect+ pulmonary stenosis+ overriding aorta)
- Transposition of great arteries
What happens at start of week 3 in embryo development?
Embryo folds longitudinally with development of the neural tube, and heart comes to lie in the thorax
