Question

Macula densa is found in
a. Internal ear
b. Kidney
c. Liver
d. Spleen

Answer 1

Hint: Collection of organs makes the organ system. Excretion is one of the vital processes as the unwanted body fluids need to come out of the body such as ammonia, urea, uric acid, carbon dioxide, water and ions like phosphate, sulphate, sodium, potassium, etc. Many organs function in this system having complex structures.

Complete answer:
> We are dealing with the excretory system and ears are not a part of this system. Ears are sense organs which helps us to hear. It has three parts namely outer ear, middle ear, inner ear which does not consist of macula densa. The internal or inner ear consists of two parts namely cochlea and the semicircular canals.

> Kidneys are the filters of blood and make it urine. Humans have a pair of bean shaped kidneys. Macula densa is the part of Kidney.
 It is the portion of the specialised cells that are closely packed which lines the wall of the DCT (Distal Convoluted Tubule). It is the thickening where the DCT meets and touches the glomerulus.

> Liver is the largest organ of our body and it is the part of the digestive system. This option is incorrect. Liver produces bile required for the breakdown of the complex food materials in the stomach for digestion and also makes proteins.

> Spleen is also not part of the excretory system and Manula densa is not a part of the spleen. It is very small in size and it also acts as a blood filter. It is responsible for identifying and removing the old or damaged red blood cells.

Hence, The correct answer is option (B).

Note: The process of excreting ammonia is Ammonotelism. Many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals. There are certain disorders of the excretory system such as uremia, kidney failure, renal calculi, etc.