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
What are someof the hormones that are necessary for fetal growth?
Insulin, IGFI (dominate in T2-T3) and IGF II (T1) and leptin, plus EGF and TGFa
What are the main effects of nutrinets on fetal growth during pregancy?
Malnurtiritoin cause symmetrical or asymmetrical growth restirction, and also the baker hypothesis and the effects that it can have in later life
What is the dominant cellular growth mechanism at o-20 weeks?
Hyperplasia
What are the dominant growth mechnisms at 20-28 weeks/
Hyperplasia and hypertrophy
What is the dominant cellular growht mechanism at 28 weeks– term?
Hypertoprhy
How is aminotic fluid procuded?
The feltal urinary tract
How is aminotic fluid recycled?
Breathed in through the fetal lungs, swolled by the fetal gi tract and also recycled over the plasma and fetal membranes
What is the main part of aminotic fluid?
98% water
What is lanugo?
A fine soft hair that covers the arms and the limbs of the human fetus
What is vernxa caseos?
A waxy or cheeslike substance ensuring that the child is not damaged by the aminotic fluid
What is meconuium?
Debris from AF plus intestinal secretions including bile
What happens if you see a green tinge to the fluid?
The fetus has oepned their bowels in uter and realeased meconium, which means that the fetus is under some form of distress
What is aminocetnetsis?
Sampling of aminotic fluid that allows for the collection of fetal cells, and is a useful dagnosticc test in fetal karyotyping
What happens with bilirubin metablolism in the fetus?
During gestation the clearance of fetal bilirubin is handed efficiently by the plams, the fetus cannot conjugate bilirubin, and therefore physioligcal jaundice is common
