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Download •There are three main excretory organs: –Lungs –Skin –Kidneys
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#66 Resources Excretory System Notes: • There are three main excretory organs: –Lungs –Skin –Kidneys (Urinary System) Renal is another word for kidney. •The liver is not an excretory organ, but produces many products which are excreted elsewhere. Toxins and drugs as well as alcohol, is broken down in the liver. •#65 is an older handout and incorrectly identified liver as an excretory organ. Urinary System Functions of the Urinary system The human excretory system functions to remove waste from the human body. During this process animals get rid of nitrogen rich waste products of metabolism, including ammonia, urea, and uric acid. There are 4 steps involved in making urine. 1. Filtration: The excretory tubes collects filtrate from the blood. Water and solutes are forced by blood pressure out of the blood and into the kidney‛s collecting tubes. 2. Reabsorption: Some valuable substances from the filtrate are returned to the blood. 3. Secretion: Other substances are extracted from the blood and added to the contents of the urinary tube. 4. Excretion: The filtrate leaves the system and the body. •Ureters = Tubes which carry filtered “liquid waste” towards the bladder. •Bladder = Storage tank for filtered “liquid waste”. •Urethra = Tube which allows filtered “liquid waste” to exit body. •Kidneys use 20% of body‛s blood •Renal Artery = Entering oxygenated blood •Renal Vein = Exiting deox. Blood •All blood is filtered through nephrons. #66 Resources Excretory System Notes: Nephron The kidney is made of many filtering parts called nephrons. Nephrons each filter blood and remove waste and return useful salts and nutrients back to the blood. Urine Formation •Filtration: –Water + Small Solutes are forced out of the blood •Reabsorption: –Water, Glucose, Amino Acids & Ions that were filtered out are pumped back into capillaries. •Secretion: –H ions, K ions, urea, and drugs/toxins out again into the urine collecting tubes. Nitrogen rich waste •Urea: Byproduct of protein metabolism in the liver. •Uric Acid: Byproduct of nucleic acid metabolism. •Creatinine: Byproduct of creatine metabolism in muscle tissue. Ureters A tube approximately 6 to 7 inches long attached to each kidney. Made up of three layers of tissue Smooth muscle Fibrous tissue Mucous layer Peristalsis , a rhythmic contraction of the ureter smooth muscle which helps to move the urine into the bladder.
