sci_bio
Kidneys and Excretion
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
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Biology · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
It is not the same as egestion (passing undigested food as faeces). The wastes are CO2, urea and excess water and salts.
Excess protein cannot be stored, so the liver removes the amino group (deamination) to form urea, carried in the blood to the kidneys.
Ultrafiltration pushes water, glucose, salts and urea into Bowman's capsule. Along the tubule, glucose and most water and salts are reabsorbed; urea stays behind as urine.
ADH raises the collecting duct's permeability, so more water returns to the blood and urine is concentrated. Less ADH gives dilute urine. This is negative feedback.
Hard words & meanings
| excretion | removal from the body of the waste products of metabolism, such as CO2 and urea |
| urea | a nitrogen waste made in the liver from excess amino acids and removed by the kidneys |
| deamination | removal of the amino group from excess amino acids in the liver, forming urea |
| nephron | the microscopic functional unit of the kidney that makes urine |
| ultrafiltration | filtering of small molecules out of the blood under high pressure at the glomerulus |
| selective reabsorption | taking useful substances (glucose, water, salts) back into the blood from the filtrate |
| glomerulus | a knot of capillaries inside Bowman's capsule where ultrafiltration occurs |
| ADH | antidiuretic hormone from the pituitary that increases water reabsorption in the collecting duct |
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