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Excretory Products and their Elimination

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Question 1
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A fall in glomeruclar filtration rat (GFR) activates

  • Juxtra glomerular cells to release renin

  • Adrenal cortex to release aldosterone

  • Adrenal medulla to release adrenaline

  • Posterior pituitary ot release vasopressin

Solution

A.

Juxtra glomerular cells to release renin

Juxtaglomerular apparatus consists of macula densa and juxtaglomerular cells. The apparatus becomes active when there is decrease in renal blood pressure or decrease in glomerular filtration rate. There is increased absorption of NaCl in ascending limb or loop of Henle. The decreased NaCl content of filtrate activates cells of macula densa to increase secretion of renin from juxta glomerular cells. Renin convert angiotensinogen to angiotensin peptides.

Question 2
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A person who is on a longer hunger strike and is surviving only on water, will have

  • more sodium in his urine

  • less amino acids in his urine

  • more glucose in his blood 

  • less urea in his urine

Solution

A.

more sodium in his urine

The normal concentration of sodium in the blood plasma is 150 mEq/L. If this level drops below 120 mEq/L, the result may be lethargy, coma or death. Unlike deficiencies of other important fluid constituents, the most common cause of this drop in sodium concentration is not a nutritional deficit of sodium, but rather an excess of water.

Question 3
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Angiotensinogen is a protein produced and secreted by

  • macula densa cells

  • endothelial cells (cells lining the blood vessels)

  • liver cells

  • juxtaglomerular (JG) cells

Solution

C.

liver cells

Angiotensinogen is a plasma protein produced and secreted by the liver cells. Renin secreted from juxtaglomerular cells and acts enzymaticaly on angiotensinogen to release 10 amino acid peptide angiotensin I.
Macula densa is actually a plaque in wall at the end of thick assending limb of nephrons.

Question 4
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Choose the correctly matched pair.

  • Inner Lining of salivary ducts - Ciliated epithelium

  • Moist surface of buccal cavity - Flandular epithelium

  • Tubular parts of nephrons - Cuboidal epithelium

  • Inner surface of bronchioles - Squamous epithelium

Solution

C.

Tubular parts of nephrons - Cuboidal epithelium

Cuboidal epithelium is present in th tubular parts of nephron (PCT and DCT). It consists of short, cube -shaped cells with round nuclei located in the centre of the cell. These cells forms microvilli to increase the absorptive surface area of the cell.
Other correctly matched points are
Inner lining of salvasry ducts is lined by compound epithelium. Moist surface of bucaal cavity is lined by compound epithelium. Inner surface of bronchioles is lined by ciliated epithelium.

Question 5
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Consider the following four statement (1-4) regarding kidney transplant and select the two correct ones out of these

1) Even if a kidney transplant is proper the recipient may need to take immuno- suppressants for a long time
2)The cell-mediated immune response is responsible for the graft rejection
3) The B-lymphocytes are responsible for rejection of the graft
4) The acceptance of rejection of a kidney transplant depends on specific interferons

The two correct statements are

  • (2) and (3)

  • (3) and (4)

  • (1) and (3)

  • (1) and (2)

Solution

D.

(1) and (2)

To prevent graft (Kidney transplant) rejection, the principle is to use chemicals, which inhibit the enitre activity of the immune system. when this occurs graft rejection is delayed. It has been show that immunosuppression may make the patients more preeen to develop cancers.One way of overcoming the problems of radiatin and immunosuppression is to suppress only the cells responsible for rejection, normally the killer T- cells .In this way, the rest of the  patients immune system would continue to function normally. The most promising approach is to treat the patient with monoclonal antibodies that recognize and destroy the killer T-cells. A monoclonal antibody has been developed, which is very effective at preventing rejection of transplanted kidneys.

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