Name: Human Respiratory System
Uploaded: 2019-07-19
Duration: 4 min 39 s
Description: Fishes need gills for respiration, while frogs have skin as one of their respiratory organs. Check out this video for details about the respiratory organs in humans.

Question

Draw a well-labelled diagram of the excretory system and explain the process of urine formation in human beings.

Accepted Answer

Removal of waste products from the body is called excretion. Excretory system of humans consists of two kidneys, two ureters, a urinary bladder, and urethra.

There are main steps of urine formation: glomerular filtration, reabsorption, and secretion. The purpose of making urine is to filter out waste products from the blood.
Just as $C O_{2}$ is removed from the blood in the lungs, nitrogenous waste such as urea or uric acid are removed from blood in the kidneys. It is then no surprise that the basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate. Each kidney has large numbers of these filtration units called nephrons packed close together. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder.
Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra.

Draw a well-labelled diagram of the excretory system and explain the process of urine formation in human beings.

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