Excretion

Question 1

The removal of metabolic wastes from the body.

Answer 1

Excretion

Question 2

The lungs excrete….

Answer 2

CO2
H2O
Heat

Question 3

Eccrine sweat glands

Answer 3

Excrete 5-10% of all metabolic wastes

99% of sweat is water – thermoregulation of body temperature (cooling)

Question 4

What does sweat also contain?

Answer 4

Also contains NaCl, urea and uric acid (both nitrogenous waste products).

Secretions help to maintain acidic pH of skin for protection against pathogens

Question 5

The Liver

Answer 5

Removes the amino group from amino acids. This forms urea and uric acid.

Breaks down red blood cells – forms bile pigments

Question 6

What are the three main nitrogenous waste products?

Answer 6

Ammonia
Uric acid
Urea

Question 7

Ammonia is..

Answer 7

the first metabolic product in the deamination of amino acids by the liver.

Ammonia is converted by the liver with carbon dioxide into urea.

Found in most aquatic animals

Question 8

Urea is

Answer 8

soluble in water and 100,000 times less toxic than ammonia.

Urea excretion uses far less water for removing nitrogenous waste -important for land animals

Found mostly in mammals, amphibians, sharks, some bony fish.

Question 9

Uric acid is

Answer 9

produced by the break down of nucleic acids. It is insoluble in water.

Found in birds, insects, many reptiles, and land snails

Question 10

The Kidney (main excretory organ)

Answer 10

Remove nitrogenous waste (toxic)
Maintain the water potential of the blood and body fluids (osmoregulation)
Maintain ion levels, e.g. potassium (K+), sodium (Na+)
Regulate the pH of blood
Regulate blood pressure long term

The kidneys concentrate waste products in urine, and reduce water loss to prevent dehydration.

Question 11

The functional unit of the kidney is called

Answer 11

Nephron

Question 12

The Nephron consists of three major parts called the

Answer 12

Bowman’s capsule
Glomerulus
Long thin tubule

Question 13

The three main stages of the kidney are…

Answer 13

Filtration
Reabsorption
Secretion

Question 14

Filtration in the kidney’s

Answer 14

Occurs in the glomerulus – blood pressure forces water, salts and other small solutes from the blood into Bowman’s capsule.

Larger blood components (e.g. RBCs and proteins) are too large to be filtered so remain in the blood.

Question 15

Reabsorption in the kidney’s

Answer 15

Occurs in the tubules

 - Proximal convoluted tubule
 - Loop of Henle
 - Distal convoluted tubule

Tubules control the concentration of substances in body fluids – amino acids, glucose, vitamins, water and some salts are reabsorbed.

Involves both passive and active transport.

Question 16

Secretion in the kidney’s

Answer 16

Occurs in the proximal and distal tubules

Adds substances to the filtrate, e.g. H+, K+, NH4+

Highly selective

Involves both active and passive transport

Question 17

Renal Hormones

Answer 17

Two main hormones involved in osmoregulation in the kidney.

Question 18

Antidiuretic Hormone (ADH)

Answer 18

• Produced by the hypothalamus, stored in the posterior pituitary gland
• Osmoreceptor cells in the hypothalamus monitor water and salt levels in the blood.
• When water levels drop, ADH is released into the blood and travels to the kidney.
• ADH changes the permeability of the convoluted tubules and collecting ducts so more water is reabsorbed into the bloodstream.
• Also increases the permeability of the collecting ducts to urea so more diffuses in from the blood.
  Increases urine concentration.

Question 19

Aldosterone

Answer 19

Hormone produced by the adrenal cortex in the adrenal gland.

Causes the convoluted tubules to reabsorb more sodium ions and decrease the reabsorption of potassium ions.

Because of osmosis, this leads to an increase in the reabsorption of water.

Increases blood volume and blood
pressure.
PPT 15.0 Slide 20