Biology · Edexcel Paper 2
The Kidneys
How the kidneys filter the blood and make urine, including the structure of the urinary system, the formation of urea in the liver, the structure of the nephron, filtration in the glomerulus and Bowman's capsule, selective reabsorption of glucose and of water, the control of the water content of the blood by ADH, and the treatment of kidney failure by dialysis and kidney transplants. Matches Edexcel 7.18B to 7.22B, which are all marked B in the specification. This chapter is for separate Biology only: Combined Science students do not need it. The effect of ADH on the collecting duct (7.20B) is for the Higher tier only.
Lessons
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1
The Urinary System and Urea
Every day the kidneys filter about 180 litres of fluid from the blood, but only about 1.5 litres leave the body as urine. This lesson is for separate Biology…
9 terms -
2
The Nephron and the Formation of Urine
Each kidney contains about a million tiny filtering units. This lesson is for separate Biology only: Combined Science students do not need it. It explains how…
9 terms -
3
ADH and Water Balance (Higher tier)
You pass a small amount of dark urine on a hot day, and a large amount of pale urine after a big drink. This lesson is for separate Biology only, and for the…
9 terms -
4
Kidney Failure, Dialysis and Transplants
When the kidneys fail, urea and excess water and ions build up in the blood, and a patient will die without treatment. This lesson is for separate Biology…
9 terms -
Knowledge organiser
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Key terms in this chapter
All 36, gathered from every lesson.
- Kidney
- An organ that filters the blood, and makes urine.
- Ureter
- A tube that carries urine from the kidney to the bladder.
- Bladder
- A muscular bag that stores urine.
- Urethra
- The tube that carries urine out of the body.
- Urea
- A waste product that is made in the liver from excess amino acids.
- Urine
- The liquid that contains urea, excess water and excess ions.
- Excretion
- The removal of waste products of metabolism from the body.
- Renal
- Relating to the kidney.
- Amino acid
- The small molecule that proteins are made from.
- Nephron
- A tiny filtering unit of the kidney.
- Glomerulus
- A ball of capillaries in Bowman's capsule, where the blood is filtered.
- Bowman's capsule
- A cup around the glomerulus that collects the filtrate.
- Filtrate
- The liquid that is filtered from the blood into the nephron.
- Selective reabsorption
- The movement of useful substances from the filtrate back into the blood.
- Loop of Henle
- The part of the tubule that reabsorbs water.
- Collecting duct
- The tube that carries urine, and in which water is reabsorbed.
- Active transport
- The movement of substances against a concentration gradient, using energy.
- Ultrafiltration
- Filtration under high pressure, in which small molecules are forced out.
- ADH
- Antidiuretic hormone, which makes the collecting duct more permeable to water.
- Pituitary gland
- The gland at the base of the brain that releases ADH.
- Hypothalamus
- The part of the brain that detects the water content of the blood.
- Permeable
- Allowing a substance to pass through.
- Collecting duct
- The tube in the kidney in which the water content of the urine is adjusted.
- Concentrated urine
- Urine with little water, and a high concentration of urea.
- Dilute urine
- Urine with a lot of water.
- Osmoregulation
- The control of the water content of the body.
- Dehydration
- Loss of too much water from the body.
- Kidney failure
- The condition in which the kidneys no longer filter the blood properly.
- Dialysis
- The treatment in which a machine cleans the blood.
- Dialysis fluid
- The fluid that contains the same glucose and ions as healthy blood, but no urea.
- Partially permeable membrane
- A membrane that allows small molecules to pass, but not large ones.
- Transplant
- The replacement of a failed organ with a donor organ.
- Donor
- A person who gives an organ.
- Rejection
- The attack by the immune system of the patient on a transplanted organ.
- Immunosuppressant
- A drug that reduces the activity of the immune system.
- Tissue type
- The pattern of antigens on a person's cells.