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Human Phys
Urine production
| Question | Answer |
|---|---|
| What are the three fundamental processes during renal excretion? | - glomerular filtration - tubular secretion: transport from blood to tubules - tubular reabsorption: transport from tubules to blood |
| How are tubules organised? | - single continuous tubule links Bowman‘s capsule to the collecting duct - specialized epithelia .single cell layered epithelia .basement membrane underneath |
| How about the structural function segmentation? | .Proximal convoluted tubule .Proximal straight .Descending part of Henle‘s loop (thin) .Ascending part of Henle‘s loop (thick) .Distal convoluted .Cortical collecting duct .Medullary collecting duct |
| How do tubules contact to blood vessels? | The close proximity of tubular epithelium and capillary endothelium enables efficient transport during secretion and reabsorption |
| Why is tubular reabsorption important? | - 180L of filtration per day - 2L urine produced per day - protects from massive fluid loss - water reabsorption concentrates urine and reattains important substances - important for overall tissue homeostasis - highly efficient process |
| How does reabsorption work? | - active or passive - filtrate flowing from Bowman’s capsule to PCT has = [solute] as ECF - active transport creates concentration gradient (water follows solutes) - peritubular capillaries favour reabsorption - low hydrostatic pressure |
| What are the steps of transport through epithelial layers? | 1) lumen to cell/cytosol 2) cell to interstitium 3) bulk transport via blood vessels - diffusion driven by osmotic/hydrostatic pressures |
| How does nephron tubular reabsorption work? | - Na+ reabsortion: an active process - in basolateral membrane - Na+ pumped into interstitial fluid - K+ pumped into tubular cell - creates Na+ gradient used for active transport |
| How do solutes move across membranes? 1) ion channels | - dependent on ion gradients - ion specific transport - transport follows gradient (downhill) |
| How do solutes move across membranes? 2) transporters | - transport against a gradient - primary active transport: chemical energy needed (ATP) - secondary active transport: Energy provided by ion gradients Symporter: Cotransport in the same direction Antiporter: Cotransport in opposite directions |
| How do solutes move across membranes? 3) Aquaporins | - increases transport of water Increased rate of water transport across membranes Driven by osmotic differences (Concentration of water/ions) |
| What are the three characteristics of mediated transport in nephrons? | 1) saturation 2) specificity 3) competition |
| How is glucose handled in the kidneys? | - when blood sugar levels are high, the kidneys are unable to reabsorb it all and some passes out in the urine - normal kidneys pass and reabsorb glucose normally |
| How is urea recycled? | - urea is filtrated in the glomerulus, but toxic in too high quantities - actively reabsorbed in different regions of tubules - enters the interstitial space - diffuses back to tubules by facilitated diffusion - reabsorbed in peritubular capillaries |
| What is fanconi syndrome? | - inadequate reabsortion in the proximal renal tubules - leads to loss of glucose, amino acids and K+ |
| How does tubular secretion work? | - improves the efficiency of waste removal - moves non filtered waste products from blood to renale tubules to be disposed as urine - driven by active transport or specific active/passive transport methods |
| How was penicillin absorption combated? | - probenecid: a competitor at the organic anion transporter - slows penicillin secretion |
| What is gout? How is it combated? | Gout is a metabolic disease caused by urate crystals forming in joints, causing pain and joint problems - combated with uricosuric agents that correct overproduction or underexcretion of uric acid |
| How does probenecid reduce uric acid absorption? | - inhibits reabsorption of uric acid through the organic anion transporter at the proximal tubules, encouraging normal excretion |
| What is clearance? | - clearance of a solute is the rate at which that solute disappears from the body by excretion or metabolism (excreted via the kidneys and not reabsorbed/secreted) - volume of plasma passing through kidneys that has been cleared of that solute |
| How is solute handling managed? | - once you have someone's GFR, you can determine how their kidneys manage solutes - measure solute plasma - filtered load of solute = solute x GFR - less solute: good kidneys - more solute: bad kidneys |
| What is BUN and creatine? | - blood urea nitrogen (test) - amino acid stored in muscles and the brain |
| Why are they important? | - BUN detects renal problems: low levels seen in malnutrition, increased levels in trauma/GI haemorrhage - creatine is important for healthy muscles and skeleton and linked to muscle mass |
Created by:
reub8n
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