3 functions of the urinary system Excrete nitrogenous wastes – Urea produced from the metabolism of proteins and nucleic acids Other animals produce ammonia or uric acid Regulate water balance Regulate salt balance

Filters the blood Produces urine (contains urea) Regulates water and salt balance

Transports urine from the kidney to the urinary bladder

Stores the urine. Has specialized expandable cells

Carries the urine to the outside of the body

Fig. 25-6d Bowman’s capsule Artery Glomerulus Distal tubule Proximal tubule Branch of renal vein Capillaries From another nephron Loop of Henle with capillary network Collecting duct

Everything in the blood smaller than blood cells or large proteins is filtered into the nephron at the glomerulus/bowman’s capsule Vital materials -sugars -amino acids -water -NaCl Are reabsorbed into the blood, so they do not leave the body Salts are secreted into urine if their concentration in the blood is too high Urine is excreted from the body

Fig Blood Kidney tubule Some drugs and poisons HCO 3 – Nutrients Medulla Bowman’s capsule Cortex H+H+ NaCl H2OH2O H 2 O NaCl HCO 3 – H + Urea Glucose Amino acids Some drugs Filtrate composition NaCl H2OH2O H2OH2O H2OH2O HCO 3 – H+H+ K+K+ Kidney tubule Reabsorption Secretion Filtrate movement Loop of Henle Collecting duct Urea Urine (to renal pelvis)

Fig Filtration H 2 O, other small molecules Capillary Nephron tubule Reabsorption Secretion Urine Interstitial fluid Excretion