Question

How is the amount of urine produced in humans is regulated?

Answer 1

Urine formation:

1. Waste is excreted from the human body, mainly in form of urine. Our kidneys generally play a major role in process of excretion.
2. Constituents of normal human urine include 95 percent water and 5 percent solid wastes.
3. It is generally produced in the nephron, which is the structural and functional unit of the kidney. Urine formation in our human body is mainly carried out in three phases namely:
   1. Glomerular filtration:
      1. Glomerular filtration seems to occur in the glomerulus where blood is filtered. The process occurs across the 3 layers- the epithelium of Bowman’s capsule, the endothelium of glomerular blood vessels, & a membrane between these two layers.
      2. Blood is generally filtered in such a way that all constituents of the plasma reach the Bowman’s capsule, except the proteins. This is the process of ultrafiltration.
   2. Reabsorption
      1. Around 99 percent of the filtrate obtained is reabsorbed by renal tubules. This is called as reabsorption. This is achieved via active and passive transport.
   3. Secretion
      1. The next step in urine formation is called tubular secretion.
      2. The tubular cells secreted hydrogen ions, potassium ions, etc. into the filtrate. By this process, the ionic, acid-base, and balance of other body fluids are normally maintained. The secreted ions combine with the filtrate and result in the formation of urine. The urine is then further passed out of the nephron tubule into a collecting duct.