| Ornithine cycle (liver) | Biomolecules / Digestion | Liver as metabolic + excretory organ; urea production from amino acid deamination |
| ADH from posterior pituitary | Chemical Coordination (Endocrinology) | Hypothalamus-pituitary axis; neurohormones |
| Aldosterone from adrenal cortex | Chemical Coordination | Adrenal cortex = mineralocorticoids (aldosterone, cortisol) |
| ANF from cardiac atria | Circulatory System | Heart as endocrine organ; atrial myocytes secreting peptide hormones |
| RAAS — renin → angiotensin | Blood pressure regulation | Kidney-heart-adrenal axis |
| Osmosis in descending loop | Cell biology / Osmosis | Same physical process as osmosis in plants and cells |
| Dialysis membrane | Cell biology / Cell membrane | Semipermeable membrane principle = same as phospholipid bilayer selectivity |
| Oedema in glomerulonephritis | Circulatory / Starling forces | Tissue fluid formation — same mechanism |
| Uricotelism in birds | Animal Kingdom / Reptiles | Link to cleidoic (amniotic) eggs in reptiles and birds |
| Brush border in PCT | Digestion | Brush border (microvilli) in small intestine for same reason: maximum absorption surface area |
| Loop of Henle – counter-current | Circulatory — countercurrent in fish gills | Counter-current exchange principle (same physics, different organ) |
| PTH → Ca2+ reabsorption in DCT | Chemical Coordination | Parathyroid gland role; calcium homeostasis |