[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › Renal, fluids and acid–base # Renal, fluids and acid–base Glomerular filtration, clearance, tubular transport, water, sodium, potassium and acid–base balance. 37 pages ## Exam priority: high - [**ADH, thirst and water balance** Regulation · The brain senses how concentrated the blood is](https://durgical.com/en/physiology/adh-thirst-and-water-balance/) - [**Distal tubule and collecting duct** Mechanism · The end of the nephron does the fine tuning: how much salt, water, potassium and acid leaves in…](https://durgical.com/en/physiology/distal-tubule-and-collecting-duct/) - [**Glomerular filtration: the barrier and its determinants** Mechanism · The kidneys filter about 180 litres of plasma a day](https://durgical.com/en/physiology/glomerular-filtration-the-barrier-and-its-determinants/) - [**Metabolic acidosis, the anion gap and compensation** Mechanism · In metabolic acidosis the blood loses bicarbonate or gains acid](https://durgical.com/en/physiology/metabolic-acidosis-the-anion-gap-and-compensation/) - [**Potassium balance** Regulation · Almost all potassium sits inside cells](https://durgical.com/en/physiology/potassium-balance/) - [**Reading an arterial blood gas step by step** Measurement · A blood gas shows the blood's pH, CO₂, bicarbonate and oxygen](https://durgical.com/en/physiology/reading-an-arterial-blood-gas-step-by-step/) - [**Reasoning through fluid and electrolyte imbalances** Table to know · Each electrolyte problem makes sense with three questions: did it move into or out of cells…](https://durgical.com/en/physiology/reasoning-through-fluid-and-electrolyte-imbalances/) - [**Renal clearance** Measurement · Clearance tells how much plasma the kidney cleans of a substance per minute](https://durgical.com/en/physiology/renal-clearance/) - [**Respiratory acidosis and alkalosis** Mechanism · Breathing too little builds up CO₂ and acidifies the blood; breathing too much blows off CO₂ and…](https://durgical.com/en/physiology/respiratory-acidosis-and-alkalosis/) - [**Sodium and extracellular volume regulation (with natriuretic peptides)** Regulation · The body's total sodium decides how much fluid sits outside the cells](https://durgical.com/en/physiology/sodium-and-extracellular-volume-regulation/) - [**The countercurrent mechanism, urea recycling and urine concentration** Mechanism · The kidney salts its medulla so it can pull water out of urine when needed](https://durgical.com/en/physiology/the-countercurrent-mechanism-urea-recycling-and-urine-concentration/) - [**Transport in the loop of Henle** Mechanism · The loop of Henle separates salt from water: one limb lets water out and the other pumps salt…](https://durgical.com/en/physiology/transport-in-the-loop-of-henle/) - [**Where and how diuretics act** Mechanism · Each diuretic blocks a salt transporter in one stretch of the nephron](https://durgical.com/en/physiology/where-and-how-diuretics-act/) ## Exam priority: medium - [**Buffers and the Henderson–Hasselbalch equation** Concept · Buffers soak up surplus acid or base within seconds and stop blood pH from swinging sharply](https://durgical.com/en/physiology/buffers-and-the-henderson-hasselbalch-equation/) - [**Daily water balance and thirst** Regulation · Each day we take in and lose about 2.5 L of water; thirst controls what goes in and the kidneys…](https://durgical.com/en/physiology/daily-water-balance-and-thirst/) - [**Dehydration and fluid overload** Mechanism · Too little or too much fluid changes blood pressure, pulse, urine and skin; the kidney tries to…](https://durgical.com/en/physiology/dehydration-and-fluid-overload/) - [**Fluid shifts between compartments** Mechanism · Water moves between cells and the fluid around them toward wherever more particles are dissolved](https://durgical.com/en/physiology/fluid-shifts-between-compartments/) - [**Functional anatomy of the nephron** Concept · Each kidney has around a million nephrons: a filter (the glomerulus) and a long tube that…](https://durgical.com/en/physiology/functional-anatomy-of-the-nephron/) - [**Glucose transport maximum and renal threshold** Measurement · The kidney reclaims all filtered glucose up to a limit; when blood glucose goes past it, glucose…](https://durgical.com/en/physiology/glucose-transport-maximum-and-renal-threshold/) - [**IV fluids: tonicity and where they go** Concept · Each IV fluid ends up in a different part of the body depending on what is in it: in the plasma…](https://durgical.com/en/physiology/iv-fluids-tonicity-and-where-they-go/) - [**Measuring GFR and plasma flow: inulin, creatinine, PAH and filtration fraction** Measurement · How we measure how much the kidneys filter and how much blood they get, using substances the…](https://durgical.com/en/physiology/measuring-gfr-and-plasma-flow-inulin-creatinine-pah-and-filtration-fraction/) - [**Metabolic alkalosis and its compensation** Mechanism · When there is too much bicarbonate in the blood, pH rises; the lungs breathe less to compensate…](https://durgical.com/en/physiology/metabolic-alkalosis-and-its-compensation/) - [**Micturition and the bladder reflex** Regulation · The bladder fills while relaxed and empties through a reflex coordinated by the sacral cord and…](https://durgical.com/en/physiology/micturition-and-the-bladder-reflex/) - [**Mixed acid–base disorders** Measurement · Sometimes two or three acid–base problems happen at once; they show up because the compensation…](https://durgical.com/en/physiology/mixed-acid-base-disorders/) - [**Physiology of acute and chronic kidney failure** Mechanism · When the kidneys filter too little, potassium, acid, water and wastes build up and kidney…](https://durgical.com/en/physiology/physiology-of-acute-and-chronic-kidney-failure/) - [**Physiology of dialysis** Mechanism · Dialysis cleans blood across a thin membrane: wastes diffuse out into a cleansing fluid, and…](https://durgical.com/en/physiology/physiology-of-dialysis/) - [**Proximal tubule transport** Mechanism · The first part of the tubule takes back two-thirds of the filtered salt and water and nearly all…](https://durgical.com/en/physiology/proximal-tubule-transport/) - [**Renal blood flow, autoregulation and tubuloglomerular feedback** Regulation · The kidney keeps its flow and filtration nearly constant even when blood pressure rises or falls…](https://durgical.com/en/physiology/renal-blood-flow-autoregulation-and-tubuloglomerular-feedback/) - [**Renal handling of calcium, phosphate and magnesium** Mechanism · The kidney decides how much calcium, phosphate and magnesium the body keeps; each one is…](https://durgical.com/en/physiology/renal-handling-of-calcium-phosphate-and-magnesium/) - [**Renal handling of H⁺ and bicarbonate** Mechanism · The kidney reclaims all filtered bicarbonate and makes new bicarbonate by excreting the acid…](https://durgical.com/en/physiology/renal-handling-of-h-and-bicarbonate/) - [**Tubular disorders by nephron segment** Table to know · Each nephron segment has its own transporters; when one fails, the urine and blood tests show a…](https://durgical.com/en/physiology/tubular-disorders-by-nephron-segment/) - [**Tubular fluid-to-plasma ratios along the nephron** Measurement · Comparing a solute's level in the tubule with its level in plasma shows, segment by segment…](https://durgical.com/en/physiology/tubular-fluid-to-plasma-ratios-along-the-nephron/) - [**Urine dilution, free water and osmotic diuresis** Measurement · The kidney can excrete water without salt (dilute urine) or hold on to it; free-water clearance…](https://durgical.com/en/physiology/urine-dilution-free-water-and-osmotic-diuresis/) - [**What the kidneys do: functions and the three basic processes** Concept · The kidneys clean the blood, keep its water, salts and acidity steady, help control blood…](https://durgical.com/en/physiology/what-the-kidneys-do-functions-and-the-three-basic-processes/) ## For completeness - [**Tubular secretion of organic acids and bases** Mechanism · The proximal tubule pulls many drugs and wastes out of the blood and dumps them into urine, even…](https://durgical.com/en/physiology/tubular-secretion-of-organic-acids-and-bases/) - [**Urine transport: ureter peristalsis and bladder filling** Mechanism · Waves of muscle squeeze urine down the ureters; the bladder stretches to hold it with little…](https://durgical.com/en/physiology/urine-transport-ureter-peristalsis-and-bladder-filling/) - [**Where extra fluid goes: blood volume vs interstitial volume** Mechanism · Small fluid gains are shared between blood and tissues; once tissue pressure turns positive…](https://durgical.com/en/physiology/where-extra-fluid-goes-blood-volume-vs-interstitial-volume/) ## A to Z - [A](https://durgical.com/en/physiology/a-z/a/) - [B](https://durgical.com/en/physiology/a-z/b/) - [C](https://durgical.com/en/physiology/a-z/c/) - [D](https://durgical.com/en/physiology/a-z/d/) - [E](https://durgical.com/en/physiology/a-z/e/) - [F](https://durgical.com/en/physiology/a-z/f/) - [G](https://durgical.com/en/physiology/a-z/g/) - [H](https://durgical.com/en/physiology/a-z/h/) - [I](https://durgical.com/en/physiology/a-z/i/) - [L](https://durgical.com/en/physiology/a-z/l/) - [M](https://durgical.com/en/physiology/a-z/m/) - [N](https://durgical.com/en/physiology/a-z/n/) - [O](https://durgical.com/en/physiology/a-z/o/) - [P](https://durgical.com/en/physiology/a-z/p/) - [R](https://durgical.com/en/physiology/a-z/r/) - [S](https://durgical.com/en/physiology/a-z/s/) - [T](https://durgical.com/en/physiology/a-z/t/) - [U](https://durgical.com/en/physiology/a-z/u/) - [V](https://durgical.com/en/physiology/a-z/v/) - [W](https://durgical.com/en/physiology/a-z/w/) [← Physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. 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