Excretory System
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Date____________________________
The excretory system is how metabolic wastes and foreign wastes are passed through,
or excreted, from the body. Many organs are involved in the excretory system,
including the skin, lungs, liver and kidneys. In the excretory system, wastes are
extracted from blood, and other bodily fluids. The excretory system also helps the body
to maintain homeostasis. By extracting wastes and other harmful molecules it helps
our bodies stay at a constant and healthy waste level. The excretory system takes
carbon dioxide, salts, and other molecules out of our bodies. The main goals of the
excretory system are to: get rid of wastes, eliminate useless by-products, eradicate
harmful chemical build up and to maintain a steady balanced chemical concentration.
The excretory system interacts with many other body systems, including the
digestive and the respiratory system. In the digestive system, food is broken down into
smaller molecules so that cells can use them. Foods will also contain some molecules
that cannot be used by cells. The blood carries gas wastes to the lungs. (respiratory
system). When there is a buildup of these wastes your body will exhale these
molecules, which is part of the excretory system because wastes are being extracted
from the body. Also, in the circulatory system, blood is being transferred to various
organs in the body. These organs will then process the blood.
Skin(eccrine glands)-The skin contains sweat (eccrine) glands which sweat and water
is excreted through. Sweat contains salt particles. So when the sweat evaporates, it
helps to regulate the salt concentration in our body. This keeps us cool. Dead body
cells are also removed through the skin.
Lungs-The lungs are responsible for maintaining life supporting levels of oxygen and
releasing (exhaling) carbon dioxide. As respiration occurs and carbon dioxide becomes
too plentiful you need to breathe out. This is how the lungs are part of the excretory
system.
Liver-The liver secrets bile that breaks down fats that are not needed. This gets rid of
unneeded wastes. The liver also takes a toxic gas called ammonia, and changes it to
urea, which is a harmless chemical.
Kidneys and Bladder- Blood passes through the kidneys and delivers unwanted
chemicals and a nitrogen rich chemical, urea (produced by the liver). The liver also
produces valuable solutes like, glucose, amino acids, ions and vitamins. The kidneys
take out all of the bad chemicals and then send all of the usable solutes back in the
blood. The kidneys filter wastes from the blood and makes a substance call urine. The
urine is then funneled into the bladder by two tubes called the ureters. The bladder
excretes about 1.5 liters of urine a day. http://thexcretory.weebly.com/index.html
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Name ________________
Date _________________
THE EXCRETORY SYSTEM
The Kidneys
Directions: Place the words from the box at the bottom of the page next to the appropriate lines
on the diagram.
Kidney
Ureter
Bladder
Urethra
Adrenal Glands
THE EXCRETORY SYSTEM
from the Human Body Systems Series
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