Week 6 - Foetal Circulation Flashcards
1
Q
What is 2,3-BPG?
A
- 2,3-biphosphoglyceric acid
- binds to two histidines in two β globins amino acid 143
- and one lysine in α
- attraction tugs on the structure
- bends and alters shape
- allosteric reaction
- O2 less readily binds
- histidine replaced by serine in foetal Hb
2
Q
Why are shunts required in foetal circulation?
A
- not send blood to organs that don’t need much
- divert bloods to a different direction
3
Q
What is the ductus venosus shunt?
A
- bypass foetal liver
- to vena cava
4
Q
What is the foramen ovale shunt?
A
- bypass pulmonary circuit
- blood goes from right atrium directly to the left one
- in heart’s septum
5
Q
What is the ductus arteriosus shunt?
A
- portion of blood bypasses lungs
- mixed blood (due to foramen ovale) joins downstream of the aorta branches
- brain receives O2 rich blood
6
Q
What changes occur at birth?
A
- to close shunts
- pulmonary blood flow increases
- alveoli inflate
- increased O2 blood in lungs
- vessels vasodilation
- decreased resistance
- umbilical vessels shut when separated from placental blood supply
- blood low pattern changed
7
Q
How does foramen ovale shunt close?
A
- right and left atria pressures are similar during foetal life
- pulmonary resistance caused back pressure in right ventrioles
- increased preload
- easy flow at birth
- right atrium pressure decreases
- increased flow from there
- increased blood flow to left atrium
- increased pressure in left atrium pushes the overlap on the left side to automatically close the shunt
- fibroblasts sew tissues together
8
Q
What are clinical defects from shunts?
A
- smaller hole may still be present
- leads to right-left shunting
- deoxygenated blood bypasses lungs as it goes directly to left atrium
- enters systemic circulation
- produces cyanosis (blue-purple discolouration and mucous membranes)
- atrial septum may not develop properly
- leads to left-right shunting
- extra volume in right atrium can cause volume overload
- hypertrophy
- heart failure
