The human body removes waste material like urea and other nitrogenous wastes from the body in the following ways:
A kidney is the main excretory organ that filters the blood containing soluble waste material and then eliminates it in the form of urine.
Urine:
Urine is formed in three main steps- glomerular filtration, reabsorption and secretion.
It comprises 95 % water and 5% wastes such as ions of sodium, potassium and calcium, and nitrogenous wastes such as creatinine, urea and ammonia.
The mechanism of urine formation involves the following steps:
Glomerular Filteration
Glomerular filtration occurs in the glomerulus where blood is filtered.
This process occurs across the three layers- the epithelium of Bowman’s capsule, the endothelium of glomerular blood vessels, and a membrane between these two layers.
Blood is filtered in such a way that all the constituents of the plasma reach the Bowman’s capsule, except proteins. Therefore, this process is known as ultrafiltration.
Reabsorption
Around 99 per cent of the filtrate obtained is reabsorbed by the renal tubules. This is known as reabsorption.
This is achieved by active and passive transport.
Secretion
The next step in urine formation is tubular secretion.
Here, tubular cells secrete substances like hydrogen ions, potassium ions, etc into the filtrate.
Through this process, the ionic, acid-base and the balance of other body fluids are maintained.
The secreted ions combine with the filtrate and form urine.
The urine passes out of the nephron tubule into a collecting duct.
Carbon dioxide:
CO2 is transported in the bloodstream to the lungs where it is ultimately removed from the body through exhalation
Feces:
The undigested waste called feces is removed after digestion from the large intestine through the rectum.
Sweat
Excess salts and fluids are excreted from the body in the form of sweat from the body.
