Metanephric vs. Opisthonephric Kidneys: Structure, Function & Differences

Metanephric and opisthonephric kidneys are distinct vertebrate kidney types.

Metanephric Kidney (Advanced)

• Structure: Two bean-shaped organs in abdominal cavity.
• Location: Higher, near lumbar region/adrenal glands (mammals).
• Function: Efficient waste filtration, electrolyte balance, water reabsorption; produces concentrated urine.
• Nephrons: Numerous; each has glomerulus, proximal tubule, loop of Henle, distal tubule.

Opisthonephric Kidney (Primitive)

• Structure: Long, ribbon-like along dorsal body wall near vertebral column.
• Location: Posterior body, near reproductive organs/cloaca.
• Function: Regulates fluid/electrolytes, waste elimination; less concentrated urine.
• Nephrons: Fewer; lack or have short loop of Henle.

Metanephric kidneys are in mammals/birds; opisthonephric in some fish, amphibians, reptiles.