Do Now What do your kidneys do? What is excreted in urine? Explain the pathway of urine starting in the kidneys.

Excretory System URINE for a real treat!!

Objectives To identify the organs of the urinary system. To explain the major functions of the urinary system. To explain the structure of the kidney and filtration system.

The Excretory System Functions: Removes certain salts and nitrogenous wastes from blood Maintains water and electrolyte concentrations Regulates pH and volume of body fluids Helps control RBC production and blood pressure

Major Organs and Functions Kidneys: removes substances from blood, form urine, regulate metabolic processes. Ureters: transports urine from the kidneys to the bladder. Urinary Bladder: stores urine Tubular Urethra: excretes urine to the outside of the body.

The Kidney… Where it all happens

Lets take a look…

Nephrons! Nephron Physiology Glomerulus filters blood  glomerular capsule receives filtrate  travels through proximal convoluted tubule and into loop of Henle (descending and ascending portions) travels through distal convoluted tubule merges in renal cortex to form “collecting duct” empties into minor and then major calyxes empties into the renal pelvis  passes into the ureter! Phew that was long. Nephron Physiology

Urine Composition Approx 95% water!! Urea: by-product of amino acid catabolism (allows us to determine amt. of protein in diet!) Uric Acid: product of metabolism of certain organic bases Electrolytes: vary with diet Interesting Fact!: you produce between 0.6-2.5 liters per day!

Micturition Aka… urination Distension of bladder triggers stretch receptors, generating a sensory impulse to the brain which triggers a motor impulse to the detrusor muscle, which contracts the bladder! (capacity is 400-600mL!) Release is controlled by the external urethral sphincter.

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