Nutrient transfer across placenta membrane Flashcards
How does gaseous exchange occur across placenta membrane?
Simple diffusion
How does carbohydrate transfer occur across placenta membrane?
Faciliated diffusion via carrier protein GLUT 1 (only glucose can cross placenta membrane
How do fats cross placenta membrane?
Because fats are insoluble they need to be broken down into fatty acids bound to albumin or as lipoproteins consisting of triglycerides attached to other lipids or proteins packaged as chylomicrons. These cross placental membrane by simple diffusion or facilitated diffusion
How do amino acids cross placenta membrane?
Secondary active transport. Amino acid is bound to sodium ion and sodium ions move down their concentration gradient
What is pinocytosis?
Micro-droplets of higher molecular mass compounds are engulfed into cytoplasm of syncytiotrophoblasts within a small vesicle and then extruded into fetal circulation.
What is pinocytosis important for transferring?
Immunologically active material
How do fat soluble vitamins cross placenta membrane?
Simple diffusion
How do water soluble vitamins cross placenta membrane?
Active transport
How do waste products cross from foetus to mother across placental membrane?
Diffusion or facilitated diffusion down concentration gradient
3 major anatomical determinants of gaseous exchange across placenta
- efficiency and flow of fetal and maternal circulation. 2. Surface area of placenta. 3. Thickness of placental membrane.
Where is the thinnest surface for gas exchange?
Syncytiotrophoblasts at the terminal villi
Does fetal haemoglobin have a higher affinity for oxygen?
Yes
Which direction does fHb shift the oxygen-haemoglobin disassociation curve?
To the left. Called the Bohr effect
Why does fHb have a higher affinity for O2?
Because 2,3-diphosphoglycerate cannot bind to fHb so does not compete with O2 like it does in normal Hb
