The kidneys are located in the lumbar region and remove metabolic wastes from the blood through nephrons, the functional units of the kidney. The nephrons filter blood in the glomerulus and selectively reabsorb certain molecules along the proximal tubule, loop of Henle, and distal tubule. Urine is collected in the calyx and exits the body through the ureters and urinary bladder. The kidneys help regulate blood pressure and the volume/composition of body fluids by controlling waste excretion and red blood cell formation.

1. Urinary system Excretion of metabolic wastes

2. Kidneys reddish brown, bean shaped, enclosed in a tough capsule. 2 – located in the right and left lumbar regions; posterior to the parietal peritoneum remove metabolic wastes from the blood and excrete to outside; urea is from protein breakdown Control rate of RBC formation Regulate blood pressure. Regulate volume, composition and pH of body fluids

3. Nephrons – functional unit of kidney Blood vessels renal arterie s – blood to kidneys renal veins – blood away from kidneys Glomerulus - where filtration occurs, fluid leaks out of blood. Is collected in Bowman’s capsule Proximal convoluted tubule, loop of Henle and distal convoluted tubule all selectively pick up certain molecules from filtrate. (loop of Henle is in the medulla, all the rest is in the cortex)

4. Urine Calyx on medial side of kidney collects what fluid is left after passing through nephrons; it is now urine 95% water, plus urea, electrolytes, amino acids kidneys can filter 45 gallons of fluid in 24 hours

5. Ureters Tubes that extend from kidney to urinary bladder peristaltic waves move urine to bladder

6. Urinary Bladder Stores urine and forces it into urethra - Micturation Some muscles contract while others relax Stretch receptors in bladder wall are stimulated by distension

7. Urethra tube that carries urine from bladder to outside Males – shares function with reproductive system; long tube Females – only used for urinating, but much shorter, females get urinary tract infections much more frequently than males

8. Kidney stones Hard little rock-like formations that occur in the calyx of the kidney Extremely painful when they pass through the ureters Thought to be caused by too much protein in the diet Ultrasound waves can shatter the stones into smaller pieces if they are unable to pass