Topic 6I: Homeostasis and Control of Blood Water Potential

Question 1

Describe how ultrafiltration occurs at the glomerulus. [4]

Answer 1

1. High hydrostatic pressure;
2. Two named small substances pass out, e.g. water, glucose, ions, urea;
3. (Through small) fenestrations in (capillary) endothelium;
4. (And) through (capillary) basement membrane

Question 2

AS is a disorder that affects kidney glomeruli. Affected individuals have proteinuria (high quantities of protein in their urine).

Suggest how AS could cause proteinuria. [2]

Answer 2

1. Affects/damages basement membrane;
2. Proteins can pass into the (glomerular) filtrate

Question 3

Creatinine is formed by the breakdown of phosphocreatine in muscles.

Suggest and explain to characteristics of a patient that could alter the creatinine concentration in the blood. [4]

Answer 3

1. Age;
2. (because) kidney function declines with age;
3. Gender;
4. (because) men and women have different muscle mass;
5. Diet;
6. (because this will) affect levels of, (phospho)creating (in muscles)

Question 4

Compare and contrast ultrafiltration and the formation of tissue fluid. [5]

Answer 4

Similarities:
1. Ions are filtered from blood;
2. Both processes occur in capillaries;
3. Proteins/cells remain in the blood;
4. High hydrostatic pressure in both processes;
5. Mainly molecules are reabsorbed back into capillaries;
6. Hydrostatic pressure gradient greater then water potential gradient in both;

Differences:
7. Filtrate enters the Bowman’s capsule in the kidney, but tissue fluid bathes cells;
8. Molecules that are not reabsorbed by capillaries form urine in the kidney, but molecules that are not reabsorbed from tissue fluid form lymph;
9. Knot of capillaries in ultrafiltration but network of capillaries in formation of tissue fluid