Question

1. Consider the urinary system

(a) What are the three basic renal processes leading to urine formation?

(b) Consider the net filtration pressure (NFP) according to the following information, Glomerular blood hydrostatic pressure (GBHP): 90 mmHg Capsular hydrostatic pressure (CHP): 35 mmHg Blood colloid osmotic pressure (BCOP): 40 mmHg Mean arterial pressure (MAP): 93 mmHg

(i) Calculate the net filtration pressure (NFP). Show your calculations.

(ii) Suppose a tumor is pressing on and obstructing the left ureter. What affect might this have on CHP and thus on NFP in the left kidney? Would the right kidney also be affected?

(c) Name the hormone that regulates plasma osmolarity. Briefly explain how the hormone works in regulating plasma osmolarity and urine formation when the body has an increase in plasma osmolarity.

Answer 1

1. a. The three basic renal process leading to the urine formation are:

i. Glomerular filtration

ii. Reabsorption

iii. Secretion

b. (i) Net filtration pressure = GBHP - (BCOP + CHP)

NFP =

(ii) The NFR will decrease due to the tumor blocking the left ureter as a result of the decrease in the GFR of the left kidney. Only the left kideny will be affected because of the left ureter blockage.

(iii) The antidiuretic hormone regulates the plasma osmolarity. It is achieved by balancing the excretion and intake of the sodium with water. The Anti-diuretic hormone (ADH) decreases the osmolarity as it increases the water reabsorption by the kidneys, which help in diluting the body fluids.

When the plasma osmolarity is low, then the secrtetion of ADH stops which results in less water reabsorption, and thus increasing the concentration of the body fluids.