Excretion Part 3 (10.3)

Question 1

What are the four key process of excretion?

Answer 1

• filtration
• reabsorption
• secretion
• excretion

Question 2

What is the nephron?

Answer 2

• functional unit of the vertebrate kidney
• made up of
  :glomerulus
  :bowman’s capsule
  :proximal tube
  :loop of henle
  :distal tube
  :collecting duct

Question 3

Information about Bowman’s Capsule:

Answer 3

• porous capillaries & specialized cells of Bowman’s capsule = permeable to water & small solutes
• small molecules move from blood across by high hydrostatic pressure into renal tubules

Question 4

What are adaptations of the glomerulus?

Answer 4

• larger diameter of afferent arteriole than efferent arteriole cause an increase in BP
• gaps between epithelial cells allows molecules to leave the blood
• basement membrane acts as a filter only allowing small molecules through + retains protein & blood cells

Question 5

What happens in the proximal tube?

Answer 5

• maintenance of pH balance
• reabsorption for the recapture of ions, water & valuable nutrients
• reabsorption of:
  Na+, Cl-, HCO3-, K+, H2O, glucose & animo acids
• secretion of”
  H+, ammonia. organic acids and bases

Question 6

What happens in the Loop of Henle?

Answer 6

• filtrate exits the ascending limb
• filtrate enters the descending limb
• 2 specialised region, thin & thick segment
• reabsorption of:
  H2O
• secretion of:
  H+

Question 7

What does the distal tube do?

Answer 7

• regulates K+ & NaCl concs. in the body
• maintains pH balance
• secretion of:
  K+, H+
• reabsorption of:
  Na+, Cl-, K+, Ca+. HCO3-, Mg+

Question 8

What happens in the collecting duct?

Answer 8

• carries filtrate through medulla to renal pelvis
• formation of urine
• reabsorption of water, sugars, amino acids, & vitamins
• reabsorption of:
  Na+, Cl-, K+, HCO3-, H2o
• secretion of:
  K+, H+

Question 9

Whats are the primary solutes affecting osmolarity?

Answer 9

NaCl - deposited by the loop of henle

Urea - deposited by collecting duct

Question 10

What is the definition of countercurrent?

Answer 10

• movement of the filtrate through the ascending limb & descending limb of the loop of henle

Question 11

What is the multiplier system?

Answer 11

multiplication of the osmotic gradient & the amount of water reabsorbed

Question 12

What is the countercurrent multiplier system?

Answer 12

• process of using energy to generate an osmotic gradient
• to enable reabsorption of water from the filtrate
• produce concentrated urine

Question 13

What the adaptations of the kidney?

Answer 13

• the length of the loop of henle = positively correlated with the need for water conservation in animals

Question 14

What is homeostatic regulation?

Answer 14

• volume & osmolarity of urine = adjusted according to an animal’s water & salt balance + its rate of urea production

Question 15

What helps to manage the omoregulatory function of the kidney?

Answer 15

• combination of nervous & hormonal control

Question 16

What is the antidiuretic hormone and what does it do?

Answer 16

• AKA, vasopressin
• produced by the hypothalamus + stored in the pituitary gland
• osmoreceptor cells monitor the osmolarity of blood, regulate the release of ADH

Question 17

How does ADH help in reducing urine volume?

Answer 17

• influences water uptake by initiating a temporary increase in no. of aquaporins in the membranes of collecting duct cells
• by influencing the hypothalamus (which generates thirst)

Question 18

What are the conditions in hypoosomotic urine?

Answer 18

• low salt

- high fluid intake

Question 19

What are the conditions in hyperosomotic urine?

Answer 19

• high salt

- low fluid intake