The Excretory System

Life Science - Middle School

The Excretory System © C opyright NewPath Learning. All Rights Reserved. 94-4907 The system of collecting the wastes produced by the body and eliminating them is the job of the excretory system. Excess water and urea are the main wastes that the body needs to eliminate. The structures of the excretory system which include the kidneys, ureters, urinary bladder, and urethra maintain a stable internal environment (homeostasis) free of harmful materials. Kidneys are organs that eliminate wastes produced by our cells. Each of the two kidneys contains about a million tiny structures called nephrons that lter blood and remove wastes but still keep the substances needed by the body. The wastes are eliminated from the body in the form of urine that’s produced in the nephrons. Lungs and Skin In addition to the kidneys, the lungs and skin remove some wastes such as carbon dioxide and water from the body as well. Carbon dioxide and some water vapor are removed from the body when we exhale. How the kidneys filter waste After entering the kidneys, blood ows through smaller and smaller arteries until it reaches capillaries in a nephron. Waste products in the blood move across from the capillaries into the urine-carrying tubes inside the nephron. These tubes are called tubules. Any needed materials by the body, such as glucose and water are kept or returned to the bloodstream by the nephrons. The waste liquid that remains in the tubules is called urine. The urine collected in the tubules empties into the ureters and then on to the urinary bladder. The Urinary Bladder The ureters carry the urine to a structure called the urinary bladder. When this structure is full, it pushes on nerves that let the body know that the bladder must be emptied. The urine leaves the body through a structure called the urethra. The sweat glands in the skin, which help to maintain a constant temperature, excrete water and urea during perspiration. urethra bladder ureter nephron lung alveoli exhalation sweat gland tubule kidney adrenal gland ureter capillaries artery vein aorta kidney ureter bladder
The Excretory System © C opyright NewPath Learning. All Rights Reserved. 94-4907 \xiBAHBDy01781tz] adrenal gland sweat gland alveoli ureters aorta urethra carbon dioxide urinary bladder kidneys urine lungs water vapor nephron Key Vocabulary Terms Describe the function of the excretory system . __________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ What are the key structures of the excretory system? ____________________________________________________ ____________________________________________________ What is the function of the kidneys ? ____________________________________________________ ____________________________________________________ How do kidneys filter wastes? ____________________________________________________ ____________________________________________________ ____________________________________________________ Lungs and Skin What are the wastes that are excreted by the lungs and skin ? ________________________________________ ________________________________________ ________________________________________ The Urinary Bladder What is the function of the urinary bladder ? ________________________ ________________________ ________________________ ________________________ ________________________