Kidney Physiology Flashcards
(32 cards)
What is meant by equilibrium between interstitial and intravascular fluid?
Equal amount of substance, no energy required, and movement occurs freely due to leaky endothelium.
What is a steady state in fluid compartments?
Constant substance amount between extracellular and intracellular fluid, requiring energy to maintain.
What recovers excess extracellular fluid (ECF)?
The lymphatic system.
What is hydrostatic pressure (HP) responsible for?
Filtration – pushes fluid out of the capillaries (~20 L/day).
What is osmotic (colloid) pressure (OP) responsible for?
Reabsorption – pulls fluid back into capillaries due to plasma proteins like albumin.
How does water diffuse in the kidney?
Freely along the osmotic gradient via Aquaporin channels.
What are the regions of the nephron?
Bowman’s capsule, PCT, Loop of Henle, DCT, Collecting duct.
What is glomerular filtration?
Passive process where hydrostatic pressure forces fluids and solutes through a membrane.
What is tubular reabsorption?
Movement of solutes and water from renal tubule back into the blood.
What is tubular secretion?
Movement of solutes from blood into the tubule filtrate.
How is glucose reabsorbed in the PCT?
Via 2nd active transport with Na+; water follows by osmosis.
What is the tubular maximum for glucose (TmG)?
260-350 mg/min or ~200 mg/dL in plasma.
What happens when glucose exceeds TmG?
Saturation occurs, leading to glucose in urine (glycosuria).
What is renal clearance (RC)?
Volume of plasma cleared of a substance per minute (mL/min).
What is glomerular filtration rate (GFR)?
Amount of plasma filtered into Bowman’s space per time unit (~180 L/day).
Name 3 manifestations of chronic renal failure.
Uraemic toxin build-up, electrolyte imbalance, renal osteodystrophy.
How does CKD affect medications?
Alters drug absorption, distribution, and elimination.
What are the 3 mechanisms for regulating blood H+?
Chemical buffers (ms), respiratory centres (min), renal system (hrs to days).
What are the kidney’s 2 main roles in acid-base balance?
Reabsorb HCO₃⁻ and generate new HCO₃⁻ from CO₂.
What is the bicarbonate buffer reaction in the kidney?
H⁺ + HCO₃⁻ → H₂CO₃ → CO₂ + H₂O; CO₂ diffuses and regenerates HCO₃⁻.
What enzyme facilitates bicarbonate buffer reaction?
Carbonic anhydrase.
What is the ammonia buffer system?
Glutamine is metabolised to NH₄⁺ (excreted) and HCO₃⁻ (reabsorbed).
What is respiratory acidosis?
CO₂ accumulation pushes reaction to generate more H⁺ (↓pH).
What causes metabolic acidosis?
Ketones (DM), diarrhoea, high protein/alcohol intake, acid ingestion.
