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Medicine LibreTexts

12.17: Excretory System Answers

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  • 1.Some of these are not examples of homeostasis: (circle those that are not)

    a. Sweating, erection of hairs and capillary dilation/contraction to control the body temperature
    b. Adjusting the rate of breathing to remove carbon dioxide from the blood
    c. Production of concentrated or dilute urine to maintain the concentration of water and salts in the blood within a narrow range
    d. Blood clotting to prevent loss of blood
    e. Reproduction to produce the next generation. Note: this is the only option in this list that is not a mechanism to maintain homeostasis.
    f. The action of the hormone insulin to keep the level of glucose in the blood within a narrow range
    g. White cells engulfing bacteria
    h. Eating to supply the body with essential nutrients
    i. Sense organs that allow the animal to sense and then remove itself from unsafe conditions
    j. Various mechanisms to keep the pH of the blood within a narrow range

    2. Fill in the left hand column with the terms/values from the list below.

    66% The proportion of the body’s water found within the cells.
    Hypothalamus The part of the brain concerned with controlling water balance.
    15% The proportion of the body’s water an animal will not survive losing.
    Thirst This is the main mechanism for diluting the blood.
    80% The proportion of an animal’s body that consists of water.
    Kidneys These organs are important for controlling water balance.

    3. Add the following labels to the diagram below of the urinary system of a mammal.

    Excretory system labelled.JPG

    4. These are functions of the kidney: (Circle 4)

    b. Controlling the concentration of water in the blood
    c. Removing urea from the blood
    f. Keeping the blood at the right pH (acidity/alkalinity)
    h. Controlling the concentration of salts like sodium and potassium chloride in the blood

    5. Match the organ with the function in the table below.

    Organ Function
    Urethra Carries urine from the bladder to the outside of the body
    Renal vein Carries deoxygenated blood away from the kidney
    Medulla The inner region of the kidney
    Sphincter Muscle that opens to allow urine to be removed from bladder
    Cortex The outer region of the kidney
    Renal artery Carries oxygenated blood to the kidney
    Renal pelvis The part of the kidney that collects the urine before it passes down the ureter
    Capsule The tough fibrous coat around the kidney
    Bladder Stores urine before it is removed from body
    Ureter The tube that carries urine away from the kidney
    Kidney Converts blood to urine

    6. Add the following labels to the diagram of a kidney below. If you like you can also colour in the diagram as indicated. :capsule- turquoise; renal artery – red; renal vein – blue; cortex - brown; medulla - pink; pelvis - yellow; ureter – green; pyramids - purple

    Kidney labelled and coloured.JPG

    7. Add the following labels to the diagram below of a kidney tubule or nephron.

    collecting duct; branch of renal artery; loop of Henle; distal convoluted tubule; glomerulus; proximal convoluted tubule; Bowman’s capsule

    Kidney tubule labelled.JPG

    8. Arrange these parts of the kidney tubule in the order in which the fluid that is being converted into urine passes through them.

    Glomerulus(G) Bowman’s capsule(BC) Proximal convoluted tubule(PCT) Loop of Henle(LH) Distal convoluted tubule(DCT) Collecting duct (CD)

    9. Indicate whether these parts of the kidney tubule are found in the cortex "C" or the medulla "M" of the kidney.

    Bowman’s capsule C
    Collecting duct M
    Proximal convoluted tubule C
    Distal convoluted tubule C
    Glomerulus C
    Loop of Henle M

    10. Match the term with its function.

    Term Function
    Renal artery Carries blood to the kidney
    Antidiuretic hormone or ADH The hormone that is involved in producing concentrated urine
    Bowman’s capsule Cup shaped structure through which the fluid part of the blood is filtered
    Collecting duct Where the majority of water is extracted from the urine
    Loop of Henle Looped portion of the tubule. Important for helping concentrate the urine
    Distal convoluted tubule Where hydrogen and potassium ions are secreted into the urine
    Proximal convoluted tubule Glucose, salts, water and amino acids are reabsorbed into the blood capillaries here
    Glomerulus Tuft of capillaries carrying high pressure blood

    11. Circle the substances in the list below that are NOT found in the fluid that has filtered through into the Bowman’s capsule of a healthy animal?

    Red blood cells; proteins; white blood cells These are large and do not pass through the holes in the walls of the glomerulus and Bowman's capsule

    12. Circle the substances in the list below that are NOT found in the urine of a healthy animal?

    Antidiuretic hormone; red blood cells; glucose; proteins; white blood cells

    13. Fill in the blanks in the statements below about antidiuretic hormone (ADH).

    a. ADH is produced by the posterior pituitary gland/hypothalamus
    b. ADH acts on the walls of the collecting ducts of the kidney tubule.
    c. When no ADH is produced an animal is said to have the condition known as diabetes insipidus
    Now cross out the option that does not apply in each of the statements below:
    d. ADH makes the walls of the collecting ducts permeable to water.
    e. ADH is secreted when the blood becomes too concentrated.
    f. When an animal is dehydrated lots of ADH is produced.
    g. When ADH is secreted the urine produced is concentrated.
    h. The main symptom of a failure to produce ADH would be lots of dilute urine.

    14. Normally all the glucose filtered into the kidney tubule is absorbed further down the tubule. If glucose is found in the urine what might one suspect to be the cause? Problems with production of insulin by the pancreas ie diabetes mellitus.


    • Ruth Lawson (Otago Polytechnic; Dunedin, New Zealand)