Excretory System Notes

Excretory System Function: maintain homeostasis by removing waste materials from the body Every cell produces metabolic wastes (waste products from chemical reactions). Excretion: process of removing wastes from the body

Excretory System The skin excretes excess water and salts in the form of sweat. The lungs excrete carbon dioxide. The kidneys play a major role in excretion.

Excretory System Kidney Function: Remove nitrogenous waste from blood (pee pee) Maintain blood pH Regulate water content of the blood

Nitrogenous Waste When protein is broken down, excess amino acids are released into the blood Proteins are made of amino acids, which have nitrogen in them The liver uses some amino acids to make useful compounds but some waste nitrogen is converted into urea (in mammals), which is the major part of urine

-Human kidneys are a pair of bean-shaped organs about 10 cm ( 4 inches) long. -Blood enters each kidney via the renal artery and exits via the renal vein. E life 32.2

-About 20% of the blood pumped by EACH heartbeat passes through the kidneys.

Structure Label your diagram: A kidney has two distinct regions: Renal medulla – inside part Renal cortex – outer part

Nephrons – the parts of the kidneys that filter out toxic substances from blood

How is blood purified? Filtration: Label your diagram: Blood is filtered in a network of capillaries called the glomerulus The glomerulus is located in a cup-shaped structure called Bowman’s capsule Label your diagram:

Materials filtered out of the blood include small molecules like water, urea, glucose, salts, amino acids, and some vitamins. Proteins, cells, and platelets remain in the blood because they are too large to pass through the capillary walls.

Reabsorption: Almost 99% of the water is reabsorbed back into the blood at the Loop of Henle – section of nephron involved in water reabsorption Material that remains is urine Label your diagram

Elimination of Urine: Ureter – carries urine to urinary bladder Urinary bladder – saclike organ where urine is stored before being excreted

-Urine leaves the body from the urinary bladder through the urethra. Sphincter muscles near the junction of the urethra and bladder control urination.

The hormone that causes the kidneys to reabsorb water is Kidney function is controlled by water intake and hormones (increase water intake = increased excretion) The hormone that causes the kidneys to reabsorb water is Antidiuretic hormone

Kidney Disorders Humans have two kidneys, but can survive with only one. If both kidneys are damaged there are two options: kidney transplant kidney dialysis Dialysis can take several hours a day & up to 3 times a week.