Name: Kidney as the Body Filter
Uploaded: 2019-07-19
Duration: 4 min 4 s
Description: The kidney is the waste manager of our body. Let us look inside the kidney and understand how this wondrous filtration system works. Watch the video now.

Question

Explain the mechanism of urine formation with neat diagram.

Accepted Answer

Urine formation occurs in the kidneys, which are two bean-shaped organs located in the abdominal cavity. The mechanism of urine formation includes three main steps:

Glomerular filtration (Ultra filtration).

Selective reabsorption.

Tubular secretion.

Glomerular Filtration: Glomerular filtration occurs in the glomerulus where the blood is filtered and this process occurs across the three layers namely, Bowman’s capsule, glomerular blood vessels (afferent arteriole and efferent arteriole), and a membrane between these two layers. The process where the blood is filtered in such a way that all the constituents of the plasma reach the Bowman’s capsule, except proteins. It is known as ultrafiltration.

Selective Reabsorption: In this process, around 99% of the filtrate obtained is reabsorbed by the renal tubules and this process is known as reabsorption and this can be achieved by the active and passive transport.

Tubular Secretion: The very next step in urine formation is the tubular secretion. Here, the tubular cells secrete some nitrogenous waste products like creatinine and substances like hydrogen ion, potassium ion, etc. into the filtrate, which helps in maintaining the ionic, acid-base and the balance of the body fluids.

The secreted ions combine with the filtrate and form urine. The urine passes out of the nephron tubule into a collecting duct, this is called tubular secretion. The urine produced constitutes 95% water and 5% nitrogenous wastes like urea, ammonia, creatinine are excreted in the urine. Apart from these, the potassium, sodium and calcium ions are also excreted.

Explain the mechanism of urine formation with neat diagram.

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