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 bloodProduces 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’scapsule

Artery

Artery

Glomerulus

Distaltubule

Proximal tubule

Branch ofrenal vein

Capillaries

Fromanothernephron

Loop of Henlewith capillarynetwork

Collectingduct

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-NaClAre 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. 25-8

Blood

Kidney tubule

Somedrugsand poisons

HCO3–

Nutrients

Medulla

Bowman’scapsule

Cortex

H+

NaClH2O

H2ONaCl

HCO3–

H+

UreaGlucoseAmino acidsSome drugs

Filtrate composition

NaCl

H2O

NaCl

NaCl H2O

NaCl H2O HCO3–

H+K+

Kidney tubule1

2

3

Reabsorption

Secretion

Filtrate movement

Loop ofHenle

Collectingduct

Urea

Urine (to renal pelvis)

Fig. 25-7

Filtration

H2O, other small molecules

Capillary

Nephron tubuleReabsorption Secretion

Urine

Interstitial fluid

Excretion