Back to AI Flashcard MakerBiology /OCR Biology A - 5.1.2 - Excretion Part 3
Function of the Loop of Henle
Osmoregulation - creates a high conc. of Na+ and Cl- in the tissue fluid of the medulla to allow water to be reabsorbed in the collecting duct Hairpin counter current multiplier
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Key Terms
Term
Definition
Function of the Loop of Henle
Osmoregulation - creates a high conc. of Na+ and Cl- in the tissue fluid of the medulla to allow water to be reabsorbed in the collecting duct Hairpin...
Collecting ducts
Where several tubules join to collect the filtrate and final sodium regulation takes place in the ureter
Features of proximal convoluted tubule
Form microvilli (increases SA for reabsorption) Many mitochondria Sodium/ potassium pump RER to synthesise proteins Co transporter proteins Vesicles t...
Selective reabsorption
All glucose, amino acids, hormones, vitamins, and 65% Na+ and Cl- and some water are reabsorbed back into the blood Na gets actively transported out o...
Survival advantage of Loop of Henle
V. concentrated urine can be produced | Conserves water and prevents dehydration
Descending limb of Loop of Henle
Water moves down conc. gradient from nephron and into surrounding fluid (high salt conc.)
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| Term | Definition |
|---|---|
Function of the Loop of Henle | Osmoregulation - creates a high conc. of Na+ and Cl- in the tissue fluid of the medulla to allow water to be reabsorbed in the collecting duct Hairpin counter current multiplier |
Collecting ducts | Where several tubules join to collect the filtrate and final sodium regulation takes place in the ureter |
Features of proximal convoluted tubule | Form microvilli (increases SA for reabsorption) Many mitochondria Sodium/ potassium pump RER to synthesise proteins Co transporter proteins Vesicles to transport substances across cell Tight junction between cells to prevent filtrate passing between cells |
Selective reabsorption | All glucose, amino acids, hormones, vitamins, and 65% Na+ and Cl- and some water are reabsorbed back into the blood Na gets actively transported out of cytoplasm of PCT cells (Na/K pump in outer membrane) Glucose or amino acids enter cells with Na+ by facilitated diffusion (co transporter proteins) Water and Cl- diffuse down conc gradient as wp has increased Blood now flowing is isotonic to tissue fluid and glomerular filtrate All diffuse into extensive network of capillaries |
Survival advantage of Loop of Henle | V. concentrated urine can be produced | Conserves water and prevents dehydration |
Descending limb of Loop of Henle | Water moves down conc. gradient from nephron and into surrounding fluid (high salt conc.) |
Ascending limb of Loop of Henle | In the lower part, fluid is v. concentrated and Na+ and Cl- diffuse out into surrounding tisues In the upper part, there is active transport of Na+ and Cl- out of the nephron. Increases water potential of fluid inside nephron (water moves out) |
Functional unit of kidney | Nephron |
Why do we call the processes in the Loop of Henle 'counter current multiplication' | Multiplies effect of gradient |
Osmoregulation | Process by which organisms regulate water content of the body |
What happens a when the water potential of the blood rises above normal | Change detected by osmoreceptors in hypothalamus Posterior pituitary gland releases less ADH Decrease in permeability of collecting ducts Dilute urine |
What happens if the water potential of the blood falls below normal levels | Change detected by osmoreceptors in hypothalamus Posterior pituitary gland releases more ADH ADH increases permeability of collecting ducts Concentrated urine |
Osmoregulation at the collecting duct | ADH released by posterior pituitary gland diffuses out of the capillaries ADH detected by cell surface receptors on the cells of the collecting ducts Cascade of enzyme reactions triggered by cAMP Vesicles containing aquaporins fuse to membranes of cells that line CD More H2O absorbed in the blood |
Aquaporins | Channel proteins for H2O |
GFR < 60 | Chronic kidney disease |
GFR < 15 | Kidney failure |
Treatment for kidney failure | Haemdialysis Peritoneal dialysis Transplant |
What does dialysate contain | Correct conc for body (same conc as normal blood) Includes water, glucose, salts and electrolytes No urea |
hCG | A hormone released by pregnant women which prevents uterus lining from shedding |
Haemdialysis | Short term Works inside body Blood from artery flows into dialysis machine w/ blood thinners where it flows through a partially permeable membrane (basement membrane) Lose excess ions and urea through diffusion Blood and dialysate flow in opp. directions to maintain countercurrent exchange system (maximise rate of diffusion) Cleaned blood returns to veins |