Question
Write the structure of a nephron and its work.
✓
Answer
→ The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen, one on either side of the backbone.
→ Urine produced in the kidney passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.
→ How is urine produce? The purpose of making urine is to filter out waste products from the blood. Just as $CO _2$ 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 a coiled tube called Bowman's capsule that collects the filtrate. Each kidney has large number 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 water there is to 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. The bladder is muscular.
→ So, it is under nervous control, as we have discussed elsewhere. As a result, we can usually control the urge to urinate.
→ Urine produced in the kidney passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.
→ How is urine produce? The purpose of making urine is to filter out waste products from the blood. Just as $CO _2$ 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 a coiled tube called Bowman's capsule that collects the filtrate. Each kidney has large number 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 water there is to 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. The bladder is muscular.
→ So, it is under nervous control, as we have discussed elsewhere. As a result, we can usually control the urge to urinate.
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