EXCRETORY SYSTEM PP 993-998

FUNCTION Every cell in the body produces metabolic waste. The skin, lungs, and kidneys make up this system.

SKIN LUNGS Excretes water, salts, small amounts of nitrogenous wastes Excretes water vapor and CO2

KIDNEYS Formation and excretion of urine Mostly water to keep wastes dissolved and easier to excrete EX. kidney stones

FILTRATION Blood forced into kidneys to clean out urea, wastes, excess water, and various substances in the blood stream

REABSORPTION Some substances return to blood maintain balance

ELIMINATION Urine passes through the ureters to be stored in bladder until it is secreted through the urethra

URINE Normally made of urea (from broken down proteins), water, and salt Very light yellow color

WHAT URINE TELLS US Proteins may leak into the urine if the kidney is damaged Too dark in color indicates dehydration Brown color indicates bleeding from the kidneys Urine will have a high glucose count if the individual is diabetic Low or no glucose indicates hypoglycemia, which results from too much insulin

Osmoreceptors in hypothalamus trigger release of ADH. Figure 44.19-2 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus Drinking reduces blood osmolarity to set point. ADH Increased permeability Pituitary gland Distal tubule STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Figure 44.19 Regulation of fluid retention in the kidney by antidiuretic hormone (ADH). H2O reab- sorption helps prevent further osmolarity increase. Collecting duct Homeostasis: Blood osmolarity (300 mOsm/L)

HOMEOSTASIS Urine production is regulated by the antidiuretic hormone (ADH) An increase in water in your blood triggers the release of ADH, causing your kidneys to take up more water to be excreted out