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25 Cards in this Set
- Front
- Back
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What is nutrition of the early and late embryo?
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Early - histotrophic
Late - haemotrophic |
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What are 2 limiting factors for substance transfer across the placenta?
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Flow-limited - permeability high, blood flow limits
Barrier-limited |
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What kind of layers do substances need to cross to cross the placenta?
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Lipid bilayers and fluid compartments
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How does water move across the placenta?
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Transcellular, paracellular and aquaporins
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What is the way to work out net water transfer?
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Difference between maternal and foetal hydrostatic and osmotic pressures
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Which proteins can move across?
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Protein transport highly restricted except for IgG
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How do amino acids move across?
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Against concentration gradient as foetal aa conc. is usually higher than maternal
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How does glucose move across?
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Facilitated diffusion - not insulin sensitive, GLUT1
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How do electrolytes move across?
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Na/K ATPase, Na-amino acid transporter
Calcium - transepithelial transport regulated by PTH |
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Which energy substrates does the foetus use?
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50% is glucose, rest is amino acid and lactate oxidation
Rather little from fatty acids (opposite of mother) |
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How much glucose is used by placenta?
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Over 50%
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What are fatty acids used for by the foetus?
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Growth and fat reserves
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How are fatty acids and TAGs transported?
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Fatty acids - serum albumin
TAGs - maternal lipoproteins |
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Why do neonate calves have less fat than human babies?
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Epitheliochorial placenta has poor diffusion of fatty acids
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How are amino acids transported across the placenta?
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Na linked active uptake
Urea diffuses out and is highly soluble IgG - receptor-mediated endocytosis |
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How is the mother's metabolism changed for uptake of nitrogen?
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Amino acids redirected to foetus from liver - urea stays low on maternal side so can diffuse across placenta from foetus
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What are the maternal adaptations of oxygen content?
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30% increase in blood volume and RBCs
30% increase in CO 40% increase in ventilation |
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What are foetal adaptations relating to oxygen content?
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High CO
Foetal haemoglobin has higher affinity for O2 Double Bohr effect Haemoglobin conc is 50% higher than maternal haemoglobin Anatomy limits intermixing of oxygenated blood and venous return from head |
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What is the maximum achievable oxygen flow for concurrent flow and countercurrent flow?
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Concurrent - foetal equilibrates with maternal venous
Countercurrent - foetal equilibrates with maternal arterial |
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Why is there insufficient equilibrium?
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Insufficient time/area
Oxygen use by placenta |
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What divides the oxygenated blood from the umbilical vein?
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Crista dividens -> foramen ovale -> left ventricle -> brain
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Where is the poorly oxygenated blood from the brain directed to?
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Right ventricle -> ductus arteriosus -> dorsal aorta
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In which species is there foetal haemoglobin?
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Ruminants - foetal haemoglobin and insensitive BPG
Other species - adult haemoglobin and low BPG in rbcs |
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What is the double Bohr effect?
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Increase in foetal pH -> increase in haemoglobin oxygen binding
CO2 transfer from placenta -> decreases pH -> O2 release from haemoglobin |
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How is CO2 transfer faciliated?
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More maternal ventilation means lower pCO2 (made up for fall in bicarbonate) -> maximises CO2 concentration gradient across placenta
CO2 20x solubility/diffusion that oxygen's |
