The nephron Flashcards
Where does ultrafiltration occur?
glomerulus and Bowman’s capsule
How does the glomerulus create high pressure?
afferent arteriole supplying the glomerulus is wider than the narrow efferent arteriole leaving
What are the 3 filters in ultrafiltration?
capillary wall of glomerulus, basement membrane and podocytes
What cant pass into the Bowman’s capsule?
cells, platelets or large plasma proteins
What filtrate enters the Bowman’s capsule?
glucose, urea, sodium, chloride, water, vitamins, hormones, amino acids
What is the role of reabsorption?
returning water, glucose and salts back to the blood
What is the name of the first tubule for reabsorption?
proximal convoluted tubule
What are the adaptations of the PCT?
- microvilli to increase SA for reabsorption
- lots of mitochondria for energy for active transport
What substances exit the PCT to return to the blood?
glucose, amino acids, vitamins, hormones and 85% of water, sodium and chloride.
How does water and sodium chloride get reabsorbed in the PCT?
water and chloride move down conc gradient out of nephron. Sodium is actively transported out
What is the conc. of the fluid that reaches the loop of henle?
isotonic
What is the role of the loop of henle?
to produce urine that is more concentrated than the blood
What moves out the descending limb?
water in the lower part as upper part is impermeable
What is the concentration of the fluid that reaches the hairpin of loop of henle and why?
hypertonic as descending limb is impermeable to sodium or chloride so they remain in the filtrate
What happens in the first section of the ascending limb?
sodium and chloride diffuses out down conc. gradient
How does sodium and chloride leave the upper section of ascending limb?
actively transported out
What is the concentration of salts in the medulla of kidney?
highly concentrated
What is the concentration of the fluid at the top of the ascending limb?
hypotonic and very dilute
How is the permeability of the walls of the DCT altered?
ADH is release from the pituitary gland
What happens in the DCT if the body lacks salt?
sodium ions are actively pumped out and chloride ions follow down electrochemical gradient
What happens in the DCT if the body wants to conserve water?
ADH is released which makes DCT walls more permeable to water and it leaves via osmosis
What is the role of the collecting duct?
to determine the final vol. and conc. of the urine
What happens to urine if more water leaves the collecting duct?
becomes more concentrated and less of it
How does the countercurrent multiplier system of the Loop of Henle work?
level of sodium in medulla becomes more concentrated further down, so there’s always a higher water potential in the convoluted tubule meaning water can always move out the whole way down
How is the permeability of the collecting duct affected?
releasing ADH from the pituitary gland
