Explain in detail the mechanism of excretion in human being class 10th
Answers
Mechanism of Excretion in Humans
The process of excretion in humans takes place in the following steps:
Urine Formation
The urine is formed in the nephrons and involves the following steps:
Glomerular Filtration
Tubular Reabsorption
Secretion
Glomerular Filtration
It is the primary step in urine formation. In this process, the excess fluid and waste products from the kidney are filtered out of the blood into the urine collection tubules of the kidney and eliminated out of the body.
The amount of filtrate produced by the kidneys every minute is known as Glomerular Filtration Rate.
Tubular Reabsorption
It is the absorption of ions and molecules such as sodium ions, glucose, amino acids, water etc. Water involves passive absorption, while glucose and sodium ions are absorbed by an active process.
Secretion
Potassium ions, hydrogen ions, and ammonia are secreted out to maintain the equilibrium between the body fluids.
The functions of the various tubules involved in the process are:
Glomerulus filters the blood
Proximal Convoluted Tubules reabsorb ions, water, and nutrients, removes toxins, and maintains the pH of the filtrate.
Descending Loop of Henle allows water to pass from the filtrate into the interstitial fluid through aquaporins.
Ascending Loop of Henle reabsorbs sodium and chloride ions from the filtrate into the interstitial fluid.
Distal Tubule reabsorbs and secretes selective ions and maintains the pH of the blood.
Collecting Duct, solutes, and water is reabsorbed from the filtrate by the collecting duct.
Micturition
The urinary bladder is stretched and gets filled with urine formed in the nephrons. The receptors present on the walls of the urinary bladder send signals to the Central Nervous System, thereby, allowing the relaxation of sphincter muscles to release urine. This is known as micturition.