NCERT Class 10 Science Chapter 6 solution Life Processes
Urine formation and regulation in Human
Urine is formed in human through a pair of bean-shaped filtering organ called the Kidney. Blood passes through it via the renal portal vein. It filters out the waste materials from the blood. Doing this also lead to filtering of useful materials like glucose, amino acids, ions. Useful materials are reabsorbed and taken back into the blood. All these processes happen in the liquid medium which is composed mainly of water. The kidney also absorbs and filter water as per the need. If the body fluid has excess water, it is secreted out. In the case of dehydration very less water is secreted to maintain the body fluid. All these regulations are controlled by hormones like Aldosterone, ADH, glucocorticoids, mineralocorticoids which in turn are controlled by blood pressure, amount of body fluid, blood osmotic pressure and minerals in body and blood.
Throughout the whole process all the minerals, nutrients, water and waste materials are absorbed and secreted multiple times. The resulting hypertonic solution is high in excretory waste, undesired minerals. The solution formed is called urine.
Events in urine formation:
Glomerulus: Filters most minerals, water, amino acids, water, urea etc. The glomerulus is impermeable to glucose and protein. Presence of glucose indicates diabetes and the presence of protein in the urine indicate proteinuria.
PCT: Proximal convoluted tubule is the major absorbing part of the nephron. It absorbs most of the mineral ion and amino acid. The resulting solution is hypotonic.
Descending limb of the loop of Henle: This part mainly absorbs water. As a result, the solution is hypertonic.
DCT: Distal convoluted tubule further absorbs the mineral ion. This process makes the urine hypotonic again.
The calcium ion is especially absorbed here.
Collecting duct: This is the final process in the formation of urine. Here absorption of water makes the solution hypertonic again.