WRITE THE INFORMATION BELOW IN YOUR NOTES:

I can identify the organs and describe the function of the Excretory System.

The Excretory System

A lot of people think the excretory system has something to do with passing solid waste from the body. Actually, it has nothing to do with that. The excretory system does have to do with eliminating

waste, but it actually eliminates it by passing it out in urine. That’s why the “excretory system” is sometimes

referred to as the “urinary system.”

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The excretory system is responsible for filtering the blood and removing waste materials in the blood. Many of these waste products are the result of cellular respiration. They consist primarily of a substance called urea, certain types of salts, and water.

The excretory system is responsible for the excretion of wastes that result from the normal operations of our cells. Remember that cells also must “eat” and pass waste. The waste from this cell metabolism then passes into our blood system. Different organs in the excretory system help eliminate these wastes from our body. These wastes are toxic to our cells and would cause the cells (and us) to die if we were not able to get them out of our bodies.

The excretory system is made up of the kidneys (and the major blood vessels that go to them), the bladder, and small tubes known as ureters.

Although not everyone includes them as part of the excretory system, the lungs, liver, and the skin also help the body to eliminate waste. The lungs, as we have learned, help us to eliminate carbon dioxide from our bodies. The liver filters toxins and other waste materials from the blood and converts the harmful nitrogenous wastes like ammonia into urea. Urea is then passed from the body through the kidney, bladder, and ureters. Urea and other liquid wastes are also released through small pores in our skin.

The Kidneys

The kidneys are bean shaped organs about 10 cm in length. They have several important functions.

•The kidneys aid homeostasis by helping the body to maintain the proper amount of water and minerals like salt. Too much water in our system throws off the balance of minerals and causes certain body systems to malfunction. Salts are important to the body, but only when the concentration is at the correct balance. (Remember how salt can affect the movement of water in and out of cells.)

•Regulations of salt are important for proper maintenance of blood pressure.

•The kidneys filter metabolic wastes like urea and uric acid from the blood.

Kidney Tissue Sample

If your kidneys are not functioning properly, a number of things could happen:

1. Water would build up in your body causing swelling (mostly evident in your fingers, toes, and lower leg near the ankles and calves. )

2. Your blood pressure could become very high or very low

3. You begin feeling very ill because the waste materials that should have been filtered out by the kidneys were not and they are poisoning your body.

4. You have difficulty urinating.5. You can develop kidney stones.

Once the waste material and water is filtered through the kidney, it passes downward through tubes known as ureters in the bladder where is stored until it is passed from the body by urinating.

Urea, water, and salts are also released from sweat glands located below the outer layer of skin (epidermis.) This “sweat” or “perspiration” passes out of the body through small holes in the epidermis called pores. Sweating or perspiring also helps the body to cool off. Body odor is actually produced by bacteria that feed on the components of sweat.

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