Question

Define excretion. Describe the process of ultrafiltration.

Answer 1

Definition of excretion

1. Excretion is the process of removal of waste and harmful products of metabolism especially the nitrogenous wastes from the body. It is carried out by the nephrons of the kidneys.

Ultrafiltration

1. Ultrafiltration is also known as glomerular filtration. This is the first step in the formation of urine occurring in the renal corpuscles.
2. The renal corpuscles include a cluster of capillaries called glomerulus enclosed within the Bowman's capsule.
3. The afferent arteriole of the renal artery enters the glomerulus and exits as the efferent arteriole.
4. The difference in diameter of the afferent and efferent arteriole results in the development of hydrostatic pressure in the glomerulus.
5. This results in the filtration of the blood through the glomerulus and the Bowman's capsule into the capsule space.
6. Except for the red blood cells, platelets, proteins, and large molecules, all the substances like ions, water, glucose, nitrogenous wastes, etc are filtered.
7. The ultrafiltration rate (GFR) is 125 ml/min in a normal adult human.