Chapter 12

1)  List 3 functions of the excretory system.

2)  Explain the term homeostasis.

3)  Identify 3 nitrogenous wastes.  How are they produced?

4)  Differentiate between excretion and elimination.

5)  Describe the role of the liver in each of the following: detoxification, bile excretion, urea formation.

6)  List the function of each component of the urinary system: kidney, ureters, urinary bladder, urethra.

7)  Label the diarams of the kidney and nephron.

8)  Give the functin of each part of the nephron.

9)  Explain the formation of urine.

10)  Why are the lungs also considered to be organs of excretion?

11)  What substances are excreted from the lungs?

12)  Describe the structure and functions of the two layers of the skin? epidermis and dermis.

13)  Describe the two skin glands: sebaceous and sweat glands.

14)  List the four main functions of the skin.

15)  How is the skin involved in homeostasis?

16)  Label the skin diagram.

2)  Homeostasis is the condition of a stable internal environment in an organism.
(glossary of terms)

3)  Three nitrogenous wastes are ammonia, urea, and uric acid.  They are formed by the breakdown of amino acids.
(Page 195)

4)  Elimination is the removal of unabsorbed and undigested food from the digestive tract in the form of feces.  Excretion is the removal of metabolic wastes.  Since unabsorbed and undigested food never enter the body cells they are not metabolic wastes.
(page 195)

5)  The liver purifies or detoxifies the blood of harmful or toxic substances.  Any harmful or toxic substances are excreted and the blood put back into the blood stream.
    The bile is produced in the liver and travels to the gall bladder to be excreted.
    When excess amino acids are injested, the liver must breakdown these.  This produces an amino group (NH2) which is converted into ammonia (NH3) which is converted to urea.
(page 199)

6)  Kidneys filter metabolic wastes and other substances from the blood, producing urine.
 
    Ureters are two tubes that carry urine to the urinary bladder.

    Urinary bladder is the temporary storage place for urine until it is excreted.

    Urethra is a tube that carries urine from the urinary bladder to outside the body.
(page 200)

7)  Be able to label fig 12-7 page 201, it appeared on my test.

9)  The formation of urine ocurrs in the nephrons in two stages, filtration and reabsorption.  Filtration occurs while the blood is flowing through the glomerulus within Bowman's capsule.  Reabsorption brings back all the vital nutrients to the blood stream such as glucose, amino acids, and salt ions.
(page 202)

10)  The lungs are considered excretory organs because they remove metabolic wastes, specifically carbon dioxide and water.
(page 203)

11)  Excreted from the lungs are carbon dioxide and water.
(page 203)

12)  Epidermis is the upper layer of the skin.  It is composed of layers of tightly packed epithelial cells.  These cells grow rapidly underneath and push existing cells out to the top where they receive less nutrition and die.  We call this dead skin.  They produce a waterproofing protein called keratin.

        Dermis lies below the epidermis and is made up of elastic connective tissue.  It is a thick layer that supports the skin and binds it to the underlying muscle and bone.
(page 203-204)

13)  Sebaceous glands produce oily secretions that keep the skin and hair soft and provide a protective coating.

    Sweat glands consist of tiny coiled tubes that open to the surface of the skin through hole called pores.  Sweat is secreted from here to cool the body off.
(page 204)

14)  The functions of the skin are:

1. It protects the internal tissues from injury, the entrance of microorganisms and it protects the body from drying out.
2. It excretes a small amount of urea and salt.
3. It holds the nerve endings which detect pain, touch, pressure, heat, and cold.
4. The skin helps to regulate body temperature.

15)  The skin is involved in homeostasis by regulating the body temperature.  The mechanisms by which the body maintains a constant temperature are a good example of homeostatic control.  These mechanisms include the constriction of blood vessels in the skin when it cold and expand when it is hot.  This controls the amount of sweat lost.  This is an example of homeostatic control.
(page 204)

16)  Be able to label the skin diagram fig. 12-8 page 203, this also was a question on my grade 11 biology test.

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