Kidney Anatomy
Kidney — Internal Structure Renal Cortex Renal Medulla (Pyramids) Renal Pelvis Ureter Renal Artery Renal Vein HilumExcretion Modes at a Glance
| Mode | Product | Toxicity | Water Need | Key Examples |
|---|---|---|---|---|
| Ammonotelism | NH3 (ammonia) | Highest | Most | Bony fish, tadpoles, aquatic insects |
| Ureotelism | Urea | Moderate | Moderate | Mammals, adult frogs, marine fish |
| Uricotelism | Uric acid | Lowest | Least | Birds, reptiles, land snails, insects |
Nephron Segment Summary
| Segment | Permeable To | Function |
|---|---|---|
| Bowman's capsule | Small molecules | Filtration start point |
| PCT | All (active + passive) | 65–70% bulk reabsorption; secretes H+, NH3 |
| Descending limb | Water only | Water exits → fluid concentrates |
| Ascending limb | NaCl only | NaCl exits → fluid dilutes; builds medullary gradient |
| DCT | Conditional (hormone-regulated) | Na+ (aldosterone), water (ADH), Ca2+ (PTH) |
| Collecting duct | Water (under ADH) | Final urine concentration; urea recycling |
Hormonal Regulation Diagram
Key Numerical Values
| Parameter | Value |
|---|---|
| GFR | 125 mL/min |
| Daily filtrate | 180 L |
| Daily urine | ~1.5 L |
| % reabsorbed | ~99% |
| Cortical osmolarity | 300 mOsm/L |
| Inner medullary osmolarity | 1200 mOsm/L |
| Nephrons per kidney | ~1 million |