Given alongside is a highly simplified (but also somewhat wrong) diagram of the human kidney cut open longitudinally. Answer the questions that follow.

(a) Define excretion.

(b) Name the functional units of the kidneys.

(c) Why does the cortex of the kidney show a dotted appearance?

(d) Mention two functions of the kidney.

(e) Write two differences in the composition of the blood flowing through the blood vessels, 'A' and 'B'.

(a) The process of removal of chemical wastes especially nitrogenous waste from the body is known as excretion.

(b) Nephrons are the functional units of the kidneys.

(c) As the cortex region contains numerous nephrons or kidney tubules, therefore, it shows a dotted appearance.

(d) Kidneys help in the following:

1. removing wastes or excretion and

2. osmoregulation.

(e) The blood vessel ‘B’ is renal artery and the blood vessel ‘A’ is renal vein.

So the blood vessel ‘B’ contains oxygenated blood with a high concentration of urea and glucose whereas the blood vessel ‘A’ contains deoxygenated blood with a low concentration of urea and glucose as compared to the renal artery.

[There is an error in the diagram. Can you identify it?]

The blood vessels A & B do not open into the pelvis or ureter but enter into the medulla