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EXCRETION Excretion is: removal of metabolic wastes removal of excess heat Main Excretory organs involved are: kidneys liver lungs skin Major Metabolic wastes: carbon CO2 and H2O are from cellular respiration certain dioxide, water nitrogen compounds Breakdown of amino acids from proteins produces nitrogen compounds Urea Ammonia Uric acid Mineral salts from metabolism Sodium chloride (NaCl) Potassium sulfate K2SO4 Excretion in other organisms: Protists diffusion into surrounding water through cell membrane excess water removed by contractile vacuoles Excretion in other organisms: Earthworms- blood filtered into nephridium tube and leave as urine through pore in the skin. Excretion in other organisms: Grasshoppers Malphigian tubules collect waste from the blood in the open circulatory system then it passes into the intestine the result is uric acid eliminated out through the end of the digestive tract (anus). Human Excretion Liver’s role Detoxificationchanges harmful substances into inactive or less poisonous substances These inactive substances are returned to blood and are filtered by kidneys. Formation of Urea in Liver: Amino acids are broken down. 1) amino group, NH2 → changed to ammonia, NH3 to urea (less poisonous) → changed Finally: Urea diffuses back into bloodstream and is filtered out by the kidneys. Urinary System Kidneys-> ureter-> urinary bladder-> urethra Kidneys 2 main functions 1. Remove wastes from cellular metabolism 2. Regulate the concentrations of substances found in the body fluids *****If kidneys cannot perform these functions a person will die.***** Kidney structure 3 layers of the kidney Cortex- outer layer blood is filtered to remove waste and excess substances Medulla- middle layer made up of tubes called collecting ducts that carry the filtered substances (filtrate) to the innermost layer of the kidney Pelvis- cavity that collects the filtrate and connects the kidney to the ureter which exits the kidney Nephron Nephron- waste filtering unit of the kidney found in the cortex and the medulla 1.25 million nephrons in each kidney Contains glomerulus, Bowman’s capsule and a renal tubule Filtration in Nephron 1. 2. 3. 4. Blood enters kidney through renal artery, small substances and wastes diffuse from the glomerulus capillaries into the Bowman’s capsule collecting cup and into the renal tubule of the pelvis, water and some dissolved substances are reabsorbed into the blood through the capillary clean blood leaves the kidney through the renal vein Urine- final waste fluid excreted Made up of water, urea and various salts. 1-1.5 liters of urine are produced every 24 hours Urinary System Parts Ureter- tube connects kidney to urinary bladder •Function –conducts urine from kidney to bladder Urinary Bladder- collects and stores urine for Excretion Urethra- during urination urine travels from the bladder to the outside of the body Lungs- remove CO2 and water (water vapor) from cellular respiration Skin Functions: 1. Protection- barrier from microorganisms and other foreign materials prevents body from drying out Skin 2. Excretion Small amounts of urea and salts in sweat Removal of excess heat (Major Function) Blood vessels dilate bringing more warm blood to skin surface Sweat is produced by sweat glands Sweat absorbs body heat and evaporates to water vapor and body heat leaves the body in the water vapor Body cools as a result of the evaporation Structure of the skin 2 layers 1. Epidermis- outer layer- made of epithelial cells top layer dead hardened cells protect lower dermis layer 2. Dermis- inner layer-made of elastic connective tissue connects skin to muscle and bone Contains blood and lymph vessels, nerves, sense receptors, sebaceous and sweat glands Excretion disorders Renal Failure- kidneys stop filtering the blood and wastes and fluid build up in the body and death can result Treatment- dialysis- artificial machine filters and cleans the blood *Presence of protein, sugar or other needed substances indicating other conditions such as diabetes and cardiovascular disease
