Compare the methods of excretion earthworms and grasshoppers.
Describe the roles of the liver, kidneys, lungs, and skin in human excretion.
Predict which areas of the skin have the most sweat glands.
Adaptations for Excretion
Describe how excretion helps maintain homeostasis.
Explain how metabolic wastes are removed from protists and hydra.
Compare the excretory structures of the earthworm and grasshopper.
Must remove metabolic wastes from body.
If not, organisms dies.
Definition: Process by which wastes and excess substances are removed from an organism.
Also removes excess heat
Helps keep body temperature constant
Organs are : lungs, kidneys, liver, skin
Works with other systems to keep homeostasis.
Major Metabolic Wastes
CO2 – formed during cellular respiration ( DS )
H2O– formed during cellular respiration ( DS )
ammonia, urea, uric acid
All others poisonous at high levels
Excretion is not elimination or defecation of feces
Excretion in Protists
Diffusion out through cell membranes into surrounding environment
Ammonia ( NH 3 )
Soluble in water
Ameba and paramecium
Water ejected from cell
Excretion in Hydra
Diffusion directly into water environment
Water enters by osmosis
No contractile vacuole, so pumped out through cell membrane
Excretion in Earthworms
Found in pairs
One on each side
Body fluid enters nephrostrome
Funnel shaped opening
Cilia beat to move fluid to each segment
Reach opening, large bladder
Drains to outside by nephridopore
Urine – dilute solution consists of water, mineral salts, ammonia, urea
Urea = ammonia and CO 2
Soluble in water
Since the earthworm lives in a moist environment, it has no problem excreting the soluble nitrogenous wastes ammonia and urea. The production of large amounts of urine – about 60 % of the earthworm’s body weight each day – results in the rapid removal of the highly toxic ammonia.
Open circulatory system
Diffusion and active transport
Uric acid, feces through anus
Uric acid does not dissolve in water
Secreted as solid or semisolid
CO2 diffuses from body tissue into tracheal tubes
12-1 Section Reviews
1. What is excretion ?
2. List the major metabolic wastes.
3. Why does excretion in the earthworm require specialized organs?
4. What animals excrete uric acid, and how does it help them?
5. Order the following nitrogenous waste products from least to most poisonous: urea, ammonia, uric acid.
Human Excretory System
Identify the principle metabolic wastes of the human body.
Describe the excretory functions of the liver.
Draw and label the parts of the human urinary system, and describe the process of urine formation.
Explain the excretory functions of the lungs and skin.
The liver is the largest internal organ and is an important organ in the human excretory system.
Purifies the blood
Changes harmful substances into inactive and less poisonous forms.
Substances returned to bloodstream and finally excreted from body by kidneys.
Disease called cirrhosis
People at Risk
Exhaust from cars
Birth control pills
Chronic pain sufferers
Exposed to pesticides
Exposed to Heavy metals
Gas station workers
Long term prescription drug therapy
Athletes using steroids
Excretion of Bile
Made by liver
Contents: bile salts, cholesterol, hemoglobin parts from worn out RBC
Some parts metabolic wastes
Collects in gall bladder pass through bile duct to small intestines
Helps digest and absorb fats
Leaves body in feces
Formation of Urea
Ammonia is converted to urea by a series of reactions called orinthine cycle.
The cycle begins when one molecule of ammonia and one molecule of carbon dioxide combine with one molecule of orinthine ( 5 carbon amino acid ) to form citrulline ( 6 carbon amino acid ).
Citrulline combines with another molecule of ammonia to form arginine ( 6 carbon amino acid ).
Arginine is hydrolyzed, forming ornithine and urea. The ornithine is reused in the cycle.
The Urinary System
Made up of:
Inside Your Kidney
Kidney ( s ) stops working:
Artificial kidney machine may be used to filter blood.
Rid body of carbon dioxide and water ( in the form of water vapor )
Cellular respiration ( Ch. 11 )
As you already know, sweat comes out of pores in your skin. As you may not know, sweat is a mixture of three metabolic wastes: water, salts, & urea. So as you sweat, your body accomplishes two things: 1) sweating has a cooling effect on the body, and 2) metabolic wastes are excreted.
Functions of the Skin
out microorganisms and foreign materials
Skin from drying out
Because it is waterproof
Secretes small amounts of urea and salts in sweat
Major role remove excess heat
Blood vessels open wider
Keeps heat in when cold
Blood vessels narrow
Body sweats less
12-2 Section Reviews
1. Name the organs of excretion in humans.
2. Name the parts of the urinary system.
3. Describe the two stages involved in the formation of urine by the nephron.
4. In what way is the nephron’s filtrate different from urine?
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