Here is a flow chart that represents the process of urine formation in the kidneys:
Start -> Filtration -> Reabsorption -> Secretion -> Concentration -> Urine
Description of the process:
1. Filtration: The process of urine formation begins with the filtration of blood in the glomerulus, a network of small blood vessels called capillaries. The glomerulus filters blood by forcing fluids and small molecules through the walls of the capillaries and into the Bowman's capsule.
2. Reabsorption: The filtered fluid then moves through the proximal tubule of the nephron, where essential substances such as glucose, amino acids, and salts are reabsorbed back into the bloodstream.
3. Secretion: In the next stage, the filtrate passes through the loop of Henle, where more water and electrolytes are reabsorbed. This is followed by the distal tubule where hydrogen ions, potassium ions, and some drugs are secreted into the filtrate.
4. Concentration: In the final stage, the filtrate reaches the collecting duct, where water is reabsorbed, and the urine is concentrated. The concentration of urine is controlled by the hormone ADH (antidiuretic hormone), which regulates the amount of water that is reabsorbed into the bloodstream.
5. Urine: Once the urine is formed, it is transported from the kidneys to the bladder, where it is stored until it is expelled from the body during urination.
End of the process.