describe the process of urine formation in kidneys for class 10
Answers
Answer:
Urine Formation
Waste is excreted from the human body, mainly in the form of urine. Our kidneys play a major role in the process of excretion. Constituents of normal human urine include 95 percent water and 5 percent solid wastes. It is produced in the nephron, which is the structural and functional unit of the kidney. Urine formation in our body is mainly carried out in three phases namely
Glomerular filtration,
Reabsorption
Secretion.
Mechanism of urine Formation
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- epithelium of Bowman’s capsule, 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 percent 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 the tubular secretion. Here, tubular cells secrete substances like hydrogen ion, potassium ion, etc into the filtrate. By 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.
Urine
The urine produced is 95% water and 5% nitrogenous wastes. Wastes such as urea, ammonia, creatinine are excreted in the urine. Apart from these, the potassium, sodium and calcium ions are also excreted.
Answer:
(i) Glomerular Filtration (filtration)
(ii) Tubular reabsorption (reabsorption)
(iii) Tubular secretion (secretion)
Explanation:
Urine formation occurs in the kidneys involves the following steps:
(i) Glomerular Filtration: Glomerular filtration is passive filtration of the blood that starts with entry of blood through glomerulus, a special ball of capillaries. The overall process leads to removal of 15-25% water and solutes from the plasma entering the glomerulus. Filtration of any substance through glomerular filtration depends on
molecular size, protein binding, ionization, polarity, and working conditions of kidney in general
(ii) Tubular reabsorption: Glomerular filtrate enters the proximal convoluted tubule wherein nutrient and salt molecules are actively reabsorbed and pushed into the peritubular capillary network while water flows passively. The filtrate is now composed of urea, some salts and water.
(iii) Tubular secretion: It includes active secretion of certain substances (H+, K+, ammonia, drug etc) from the peritubular capillary network into the distal convoluted tubule.
The urine formed is collected in the urinary bladder.