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1/9/2015 The Excretory System Biology 11 Function y The excretory system eliminates non-solid wastes from the body. y Included are: 1. Lungs (CO2 2. 3. 4. and water vapor from respiration) i ti ) Skin (loses some salt, urea**, and water through pores/perspiration) Large Intestine (bile and wastes like cellulose and fiber) Renal System (nitrogenous wastes from metabolism) **Urea Amino acids contain the functional group “amino,” NH2. y When proteins are broken down, excess amino acids cannot be stored by the body and d are removed d (d (deamination) i i ) by b the h liver. y The amino group is converted into ammonia, which is converted into a less toxic substance, urea, through a series of enzyme-catalyzed reactions. y 1 1/9/2015 Urea y Kidneys will transport the urea from blood to urine. Renal System aka urinary system or urinary tract Made up of: 1. Kidneys – y y ◦ bean-shaped organs that control concentrations off substances bt in i the th body b d and d filters filt metabolic t b li wastes. Ureters – 1. ◦ two, 25-30 cm, tube-like structures (one for each kidney) that carry urine from the kidneys to… Urinary Tract (continued) (Urinary) Bladder 3. ◦ ◦ Temporary storage site for urine Can hold anywhere from 300 mL to 400 mL, person dependent, due to the elastic-like muscle. Urethra 4. ◦ tube to carry urine and excrete outside of body. 2 1/9/2015 1. Kidney - Function The principal function of the kidney is to filter blood in order to remove cellular waste products from the body. y At any given time, 20 % of blood is in the kidneys. Humans can function with one kidney. y If one ceases to work, the other increases in size to handle the workload. y y y The kidneys help to maintain homeostasis by filtering the blood. The kidneys are fistsized, bean shaped structures. – two layers: medulla and d cortex – filtering units called nephrons – renal artery and renal vein cortex medulla renal artery renal vein ureter (to bladder) capsule 3 1/9/2015 The kidney can also excrete other waste products, such as : y 1) urea a nitrogenous waste produced in the liver from the breakdown of p protein. It is the main component of urine y 2) uric acid usually produced from breakdown of DNA or RNA y 3) creatinine waste product of muscle action. Kidney Function y 3 basic functions in maintaining homeostasis: 1. remove waste from blood 2 help 2. h l to maintain i i electrolyte, l l pH, H and fluid balances 3. release key hormones 4 1/9/2015 y y y y Because most of our diet is acidic, the kidney help produce ammonia which help to neutralize. Every 24 hours, about 180 L of blood is filtered. filtered Much of the filtered fluid is reabsorbed while approx. 1.5 L of urine is produced each day. Sometimes essential substances are filtered out of the body; these can be detected in urine to help diagnose disease or illness. from body Nephrons • • • Nephrons are the filtering units in the kidneys. They clean and rebalance b l the h bl blood d to body to produce urine. loop of Henle There are approximately 1million nephrons in each kidney to body from other nephrons from body t body to b d to body loop of Henle from other nephrons 5 1/9/2015 Nephron y Each nephron is made up of cup-shaped structure called the Bowman’s capsule. • This narrows into a long coiled tubule. tubule • In the center of each capsule is a mass of capillaries called the glomerulus. Bowman’s capsule 6