Nephron, GFR, countercurrent mechanism, RAAS, acid-base, digestion, gut microbiome.
Renal And Gi Physiology
Nephron
Functional unit of the kidney (~10⁶ per human kidney). Glomerulus filters plasma; tubule (proximal, loop of Henle, distal, collecting duct)…
Glomerular filtration (GFR)
Plasma-ultrafiltration by glomerular capillaries + slit diaphragm. GFR ~125 mL/min in healthy adults; net filtration pressure = P_GC −…
Countercurrent multiplier
Loop of Henle generates corticomedullary osmotic gradient (300→1200 mOsm) by active NaCl reabsorption from ascending limb + passive water…
Renin-angiotensin-aldosterone system (RAAS)
Blood-pressure + volume regulator. Low pressure → juxtaglomerular cells secrete renin → angiotensinogen → Ang I → (ACE) Ang II →…
Digestion
Mechanical + enzymatic breakdown of food into absorbable monomers. Stomach (HCl, pepsin), small intestine (pancreatic…
Gut microbiome
~10¹³-10¹⁴ bacteria + archaea + fungi + viruses colonising mammalian GI tract. Contributes ~150× host gene count; synthesises vitamins B/K,…
Tubular reabsorption
Na⁺-coupled cotransport of glucose/amino acids in proximal tubule; ~99% of filtrate reabsorbed. Aquaporin-2 (collecting duct) under ADH…
Acid-base balance
Henderson-Hasselbalch pH = 6.1 + log([HCO3⁻]/0.03 PaCO2). Lung regulates CO2 (fast); kidney regulates HCO3⁻ (slow). Anion gap classifies…
Liver function
Metabolic hub: gluconeogenesis, urea cycle, bile synthesis, drug metabolism (CYP450), albumin + clotting-factor synthesis. Portal…
Pancreatic function
Exocrine: zymogen granules (trypsinogen, lipase, amylase) secreted via CCK stimulation. Endocrine islets: α-cell glucagon, β-cell insulin,…