31 Years NEET Previous Year Questions: Excretory Products & Their Elimination

Diabetes mellitus leads to a complex disorder called prolonged hyperglycemia, which is associated with loss of glucose through urine known as glycosuria and when the cell are unable to utilize carbohydrates for energy instead they use fats & proteins, and degradation of these fats produces ketone bodies.  The presence of these ketone bodies in urine is known as ketonuria.

The counter current mechanism helps to maintain a concentration gradient in the medullary mterstitium. The proximity between the Henle’s loop and vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e., from 300 mOsmoIL-1 in the cortex to about 1200 mOsmolL-1 m the inner medulla. This gradient is mainly caused by NaCl and urea. Presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine).

Uric acid is the chief nitrogenous component of the excretory product of cockroach. Animals which live in dry conditions have to conserve water in their bodies. Therefore, they synthesise crystals of uric acid trom ammonia. Uric acid crystals are non-toxic and can be retained in the body for a considerable time. Uricotelic animals include most insects e.g. cockroach, reptiles and birds.

Urine formation involves three main process called, glomerular filtration, reabsorption and secretion. A comparison of the volume of the filtrate formed per day (which is 180 litres per day) with that of urine released (about 1.5 litres) suggest that nearly 99 percent of the glomerular filtrate is resorbed by the renal tubules. The descending limb of loop of Henle is permeable to water but impermeable to electrolytes.
The ascending limb is impermeable to water but allows transport of electrolytes.
Reabsorption of sodium ions and water takes place in distal convoluted tubule.
Also, it is capable of reabsorption of HCO₃.

The principal nitrogenous excretory compound in humans is urea. It is synthesized in the mitrochondrial matrix and cytosol of liver cells and eliminated through kidneys.

Tissue and blood group matching are essential before undertaking kidney transplant. Even if kidney transplant is proper, the recipient may need to take immuno suppresant all his/her life. The ability of body to differentiate self and nonself and the cell-mediated immune response is responsible for graft rejection.

Glome podocytes are highly specialized cells with a complex cytoarchitecture plays a major role in establishing the  selective permeability of glomerular filtration barrier.

When some one drinks lots of water, kidney release of ADH is suppressed.

An uricotelic organism produces uric acid as a result of de-amination. Examples of such organism are birds and insects.

Nearly all the essential nutrients, and 70-80 percent of electrolytes and H₂O are reabsorbed by proximal convoluted tubules.

Those animals that excrete ammonia are called as ammonotelic, eg. aquatic amphibia. Those animals that excrete urea are called as ureotelic, eg. frog, humans.
Those animals that excrete uric acid are called as uricotelic, eg. pigeon, lizards, and cockroach.

 The amount of the filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). GFR in a healthy individual is approximately 125 ml/ minute, i.e., 180 litres per day. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal. Renin converts angiotensinogen in blood to angiotensin I and further angiotensin II. Angiotensin II being powerful vasoconstrictor increases the glomerular blood pressure and thereby GFR

Adult frog and human exhibit ureotelism because there excretory waste product is urea.

A – Adrenal gland – located at the anterior part of kidney, secrete Catecholamines which stimulate glycogen breakdown.

Option ( c) is correct answer. 

Explanation :- 

As Housefly - Malpigian Tubules - Uric acid

Rohu - Kidney - Ammonia

Peacock - Kidney - Uric acid

Salamander - Kidney - Urea