Question

In the frog kidney, the cortex and medullary region are
A. Less distinct
B. More distinct
C. Absent
D. None of the above

Answer 1

In anatomy and zoology, the cortex is defined by the most superficial layer of an organ. It is a special type of epithelial tissue made in order to protect sensitive organs.

Complete answer:
In the kidneys, the outer space between the renal capsule and medulla is known as Renal Cortex. This portion is responsible for ultrafiltration of the kidneys. Medulla is the innermost or middle layer of an organ. In kidneys, the renal medulla is mainly concerned with containing the structures of the nephrons that are responsible for maintaining the salt and water balance of the blood.
Just like humans, frogs (amphibians) also have two kidneys. They use their kidneys to replace the water lost through evaporation in the skin whenever they are not in water. The Three basic excretory organs are pronephros, mesonephros and metanephros.
Pronephros are the basic types of excretory organs which correspond to the first stage of kidney development. The functional kidney of a frog tadpole is pronephros that has been developed from nephrotomes in the anterior regions.
Pronephros is succeeded by the mesonephros. It is the main excretory organ of aquatic vertebrates such as fish and amphibians and functions as a temporary kidney in reptiles, birds, and mammals. The mesonephros acts as a structure like the kidney. The functional kidney of a frog is mesonephros.
Metanephros is the third type of embryonic excretory organs found in higher vertebrates. These are the permanent and functional kidneys.
We can’t see the loop of Henle in case of frogs and the Malpighian tubules are scattered in the kidney. In this regard, we can say that in a frog's kidney, the cortex and medullary organ are absent.

Hence, option C is correct.

Note: It is very essential to understand that the use of cortex is to guard the delicate organs but in the organisms with lower levels of body structure, the need of a tissue covering is ignored. In cases of frogs, we can see that the excretory wastes are drained from the coelomic fluid into the coelom by an opening of the kidney, which is called nephrostome.