Biology [2 Mark Question Answer]

There is frequent urination in winter than in summer. In winter, the less sweating occurs than summer. So, more water given out from the kidneys is in the form of urine.

The renal cortex has a dotted appearance because it contains several tiny tubes or complex structure known as nephrons. Nephrons are microscopic structural and functional unit of kidney which give the outer cortex 'dotted' appearance.

Urine is slightly thicker in summer than in winter. In summer season, good amount of water is lost through sweating or perspiration from the body to keep the body temperature normal. In turn, kidneys have to reabsorb more water from the urine, thus making it more concentrated or thicker.

Tubular Secretion : This process is the reverse of tubular reabsorption. In this the proximal convoluted tubule removes waste materials from the blood and pass these into the filtrate by the process of secretion. Uric acid, ammonia, urea, creatinine and some other molecules are removed by this process of tubular secretion.

Dialysis : Dialysis is a process of separating small molecules from larger ones using a semipermeable membrane; in the kidneys and the glomeruli act as semipermeable dialysis bags. In case of kidney failure, an artificial kidney machine works on the principle of dialysis to purify the blood.

Osmoregulation : The process of control of water content and concentration of ions in the body is called osmoregulation. Osmoregulation is brought about by kidneys. Osmoregulation is very important as the blood plasma should be maintained at the right concentration.

Excretion: The removel of waste products (toxic metabolic wastes) formed in the body, produced by metabolism and the substences present in excess, is called excretion. If the waste producte are not removed, they may poison cells or may alow down the metabolism.