Excretory and Urinary System

Excretory and Urinary System Homeostasis - Thermoregulation- how animals maintain internal temperature. - Osmoregulation- how animals maintain solute balance with gaining and losing water - Excretion- Elimation of metabolic wastes, such as urea

Heat flows from a warm object to cooler objects so animals must have adaptations to maintain homeostasis and counteract the heat loss.

Thermoregulation External Regulation- animals physically regulate body temperature in 4 ways: 1. Conduction- direct contact with heat source. Ex) hippo sitting in cool pond 2. Convection- heat transfer through air movement. Ex) breeze 3. Radiation- releasing electromagnetic waves. Ex) Lizard sunbathing 4. Evaporation- Cooling effect by losing water vapor. Ex) Dog panting and sweating

- Ectotherm- Animals with low metabolic rates and depend on the environment for body temperature. Ex) Invertebrates, Fish, Amphibians, and Reptiles - Endotherm- Animals with high metabolic rates, which generate enough body heat for their own regulation. Ex) Mammals and Birds

Internal Regulation- Physiological/ behavioral adjustments - Some animals warm themselves by vasodilation, which increases the size of the blood vessels, thus increasing blood flow. Vasoconstriction does the opposite. - Torpor- An adaptation that saves energy by going into a state of low metabolism. Ex) squirrels hibernating during the winter or bats sleeping during the day

Excretion

- Metabolic wastes- ammonia, CO2, salt, and food wastes - When amino acids break down, toxic ammonia is produced - Any organism that cannot immediately release ammonia must change it to a less toxic substance- urea or uric acid - Excretory organs filter wastes out of body fluids EX: nephridia, Malpighian tubules, lungs (gills), sweat glands.

Osmoregulation- management of the body’s water and solute concentration. - Different for marine, freshwater, and terrestrial organisms Nitrogenous Wastes

1. Ammonia- highly toxic; excreted by marine animals (hydra, fish) 2. Urea- excreted by earthworms and humans 3. Uric Acid- Not soluble in water; paste-like; excreted by insects, reptiles, and birds

Kidneys- osmoregulator and organ of excretion in humans - The functional units of kidneys are nephrons (filtration, secretion, reabsorption, and excretion) - Blood flows into a glomerulus (a cluster of capillaries) - Fluid (filtrate) leaves blood and enters Bowman’s capsule; dissolved molecules are carried by the filtrate - Filtrate travels through the proximal convoluted tubule, good parts are reabsorbed by the body - Filtrate flows through the loop of Henle. Much of the fluid is reabsorbed - Concentrated urine flows through distal convoluted tubule into the collecting duct, then through the ureter to the urinary bladder for storage. - Urine is excreted out through the urethra

Hormones

- Aldosterone- (secreted by the adrenal cortex) controls salt reabsorption - Antidiuretic hormone (ADH)- (produced by the hypothalamus and released by the posterior pituitary) controls water reabsorption; alcohol blocks the release of ADH, resulting in increased urination and even dehydration - Renin-angiotensin-aldosterone System (RAAS)- reabsorption of water based on blood pressure

Sweat Glands

- Salt, water and some wastes are filtered from the blood into sweat glands for evaporation through the skin.