Fetal Physiology Flashcards
Where can you find the fetal villi?
Suspended in intervillous spaces that are balmed in the maternal blood
What are the factors promoting O2 exchnage to fetus at the placenta?
Increased maternal production of 2,3 DPG
Fetal haemoglobin
The double bohr effet
What is the structure of fetal haemoglobn?
The predominant form is HbF, 2 aplha subunits + 2 gamma subunits, and has a greater affinitiy for oxygen as does not bind 2,3 DPG as effectively
How does the double bohr effect work?
In the mother, as CO2 passes into intervillous blood, the pH decreases, and the bohr effect decreases the affinity of Hb for O2
In the fetus is the CO2 is lost the Ph rises, and the bohr effect causes an increased affinity of HB for O2
What is the main respiraoty maternal adapation to pregancy?
There is progesterone drive hyperventiliation, which blows of more CO2 and less pCO2 is left in maternal blood and creates a concentration gradient
What is the double haldone effet?
The amount of oxygen binding influences the amount of CO2 that is picked up, as Hb gives up O2 it can accept increasing amounts of CO2, the fetus givens up CO2 as O2 is accepted
What is the circulatory chunt that bypasses the liver?
The ductus venosus
What is the circulaotry shunt that goes from the Ra to the LA?
The foramen ovale
What is the shun that goes from the pulmonary trunk to the aorta?
The ductus ateriosus
Why is the ductus venosus needed?
By ensuroing shunting of blood around the liver the satruation of oxygen is mostly maintained
What is the role of the free border of the septum secundum>?
Forms a crest called the crista dividens, and creates streams of blood flow so that the majority flows to the LA, and a minor proportion flows to RV mixing wiht blood form the SVC (deoxygenated)
Why is the ductus ateriousus needed?
Shunts blood from teh RV and the PT to the aorta, and joins the arota distal to the supply to the head and the hear and therefore minisiming the drop in the O2 staruation
What are some of the fetal responses to hypoxia?
Resdistrubtuin of flow to protect the supply to the heart and the brain, and the fetal heart rate flors in response to hypoxia.
Why does the fetal heart rate slow in repsonse to hypoxia?
Fetal chemoreceptros detec a decreased pO2 or an increased pCO2, and there is vagal stimulation which then leads to bradycardia, and in comparisaion to the adult where vagal inhibition leads to tachycardia
What are some of the effects of chonric hypeoxaemia and what can cause it?
In women who smoke, causes growth restriction, and behavioural changes as you will see less movment and evidence of the sleep state
