Urine Formation in Mammalian Nephrons

Filtration

Blood subset forms in Bowman's Capsule.

Bowman's Capsule

Structure where filtrate enters from glomerulus.

Convoluted Tubule

Site of solute reabsorption and secretion.

Selective Reabsorption

Necessary solutes reabsorbed into peritubular capillaries.

Tubular Secretion

Solutes secreted from capillaries into tubule.

Collecting Ducts

Final urine concentration occurs here before excretion.

Loop of Henle

Establishes sodium ion concentration gradient.

Renal Cortex

Outer region containing glomeruli and Bowman's capsules.

Renal Medulla

Inner region where Loop of Henle is located.

Aquaporins

Water channels in collecting duct walls.

Antidiuretic Hormone (ADH)

Regulates aquaporin permeability in kidneys.

Dehydration

Condition causing aquaporins to open, conserving water.

Hyperosmotic Urine

Urine more concentrated than blood plasma.

Sodium Ion Gradient

Concentration increases from cortex to renal pelvis.

Fluid Requirements

Body's hydration level affects collecting duct permeability.

Alcohol

Inhibits ADH release, leading to increased urination.

Caffeine

Similar to alcohol, increases urine production.

Desert-Dwelling Rodents

Produce urine 25X more concentrated than blood.

Concentration Gradient

Established by Loop of Henle for urine concentration.

Peritubular Capillaries

Surround convoluted tubules, facilitating reabsorption.