30.4 Excretory System Structures in the Excretory System. Functions of the Excretory System Control of the Excretory System Excretion • This is the process your body uses to excrete metabolic wastes and maintain homeostasis. • An example of metabolic waste is ammonia. Structures in the Excretory System •Skin •Lungs •Liver •Kidney Skin • Excess water, salts and small amounts of toxins (urea) are released in sweat. • This occurs in small amounts that may not be noticeable. The Lungs • Carbon dioxide is exhaled from the lungs along with water vapor The Liver • The liver converts dangerous nitrogenous wastes into less dangerous, less toxic, substances. • For example: Ammonia into urea. The Kidney The Kidney •The major organ involved in excretion •Filters metabolic wastes from the blood •Produces urine Functions of the Kidney • Filtration • Reabsorption • Urine Excretion Filtration • Passing a liquid or gas through a filter to remove wastes or impurities. • Example (location) • Glomerulus: a dense network of capillaries encased in the Bowman’s Capsule Reabsorption • The filtrate is moved through the tubules, and down the loop of Henle. • As the filtrate moves through the loop, salts and water are moved out of the tubule and back into the veins and arteries. Urine Excretion • Once reabsorption is complete, the filtrate passes into the collecting duct. The urine then moves down the ureter, into the bladder, and out the urethra. Kidney Control • ADH, Anti-diuretic hormone or vasopressin, controls how much water can pass out of the tubule and back into the body. Kidney Stones • Form when different substances crystallize in your kidneys. • Most kidney stones are formed from calcium • High fat and salt diets in people over 40 lead to kidney stones Diabetes and the Kidneys Classwork • Imagine you just ate a bowl of chicken noodle soup, follow the soup through the digestive system and then through the excretory system.