The Excretory System

STRUCTURES  Kidneys – filter blood of wastes  Ureter – tube leading to bladder  Urinary bladder – smooth muscle bag that stores urine

Specifics…  KIDNEY –Nephrons – filtering unit of kidney. –Blood enters nephron carrying wastes. –Blood travels into the capillaries of the nephron called the glomerulus –In the nephron, under high pressure, water, glucose, vitamins, amino acids, protein wastes, salts, and ions from the blood pass out of the blood into a part of the nephron called the Bowman’s capsule.

Kidney Nephron Glomerulus Bowman’s capsule

Specifics… –Bowman’s capsule – part of nephron –As liquid passes into the capsule it passes through a narrow, U-shaped tubule that reabsorbs water, glucose, and amino acids. Water also diffused back into the blood capillaries.

Formation of urine!  Urine – liquid that remains in the tubule: composed of excess water, waste molecules, and excess ions  YOU PRODUCE ABOUT 2L OF URINE PER DAY!!!

Waste flows out of the kidneys, through the ureter into the urinary bladder, and out of the body through a tube called the urethra.

Urinary System and Homeostasis  Major waste products – ammonia and urea –THESE ARE TOXIC TO THE BODY!  Kidneys control level of sodium in blood by removing and reabsorbing sodium.  Kidneys regulate pH of blood as well.

Urine Regulation  Hypothalamus - small part of brain that controls many body processes –Produces hormone ADH (antidiuretic hormone) that stimulates reabsorption of water in a nephron.