3 Boardworks GCSE Separate Sciences 2009 The Kidneys Waste removalBoardworks GCSE Separate Sciences 2009The KidneysSeveral organs are important in removing waste from the body.The lungs remove carbon dioxide.The liver converts excess protein into urea.The skin provides a surface for small amounts of water and salt to move out of the body.The kidneys remove unwanted substances such as urea, excess water and salt.
4 Boardworks GCSE Separate Sciences 2009 The Kidneys What is urea?Boardworks GCSE Separate Sciences 2009The KidneysExcess amino acids in the body are broken down by the liver, producing a waste substance called urea.This process is important because it converts toxic ammonia to urea, which is done using carbon dioxide.Once formed, urea is transported by the circulatory system to the kidneys.The kidneys filter the blood, removing urea and excess water and salt, which forms urine. Urine is stored in the bladder before being excreted from the body.Teacher notesThe kidneys typically filter about 1,500 litres of blood every day.
5 What are the different parts of a kidney? Boardworks GCSE Separate Sciences 2009The Kidneys
6 How does the kidney work? Boardworks GCSE Separate Sciences 2009The KidneysTeacher notesStage 1: Filtration occurs as an increased blood pressure forces smaller substances through the capillary wall into the Bowman’s capsule. The glomerulus is a ball of blood vesselsStage 2: In the first coiled tubule (proximal convoluted tubule) most reabsorption is by active transport. The cells of the first coiled tubule are packed with mitochondria, and have large brush borders to increase the surface area for reasborption.Stage 3 & 4: Substances move out of the loop on Henle by passive diffusion. The cells of the loop of Henle are thin, with no brush border and relatively few mitochondria.Stage 5: The collecting duct carries water to the ureter.
8 Controlling water levels Boardworks A2 BiologyHomeostasisOsmoregulation is the process by which organisms regulate the water content of the body.Mammals need to ensure the volume of blood plasma and concentration of dissolved substances in the blood and tissue fluid stay relatively constant.Osmoreceptors in the hypothalamus monitor the water potential of the blood. This varies the amount of antidiuretic hormone (ADH) released into the bloodstream. The kidneys respond to a change in ADH concentration by adjusting the volume and concentration of the urine.
9 Boardworks A2 Biology Homeostasis OsmoregulationBoardworks A2 BiologyHomeostasischange detected by osmoreceptors in the hypothalamuspituitary gland releases more ADHADH increases permeability of collecting ductsmust conserve waterdecrease in water potentialnormal water potential of bloodconcentrated urinedilute urineincrease in water potentialmust expel excess waterdecrease in permeability of collecting ductsTeacher notesHigh concentrations of ADH in the blood also induce the feeling of thirst in the animal. This helps to increase the body’s water content.change detected by osmoreceptors in the hypothalamuspituitary gland releases less ADH
18 What is a kidney transplant? Boardworks GCSE Separate Sciences 2009The KidneysKidney failure can also be treated by giving a patient a kidney transplant. This involves replacing the damaged kidney with a healthy kidney from a donor.Healthy organs can come from a living or recently deceased person. Living donors are often close friends or relatives of the patient.In the US there is an organ donor register. By joining this people agree to the donation of their organs and tissue for transplantation after their death.Other organs and tissues that can be donated include blood, bone marrow, heart, lungs and cornea.
19 Kidney transplant data Boardworks GCSE Separate Sciences 2009The KidneysTeacher notesData from the NHS website:This website also contains a lot of other useful information on organ donation and transplants.
20 Preventing organ rejection Boardworks GCSE Separate Sciences 2009The KidneysAll cells contain markers on the surface, called antigens. These help the immune system identify a cell as a cell from the body or a foreign cell.If the immune system detects a transplanted organ as a foreign object, it may mount an immune response against it. This is called organ rejection. Several steps are taken to prevent this:A donor kidney of a similar ‘tissue type’ as the patient, is used. This means that the antigens on the new organ will be as similar as possible to those of the patient.Teacher notesSee the Boardworks GCSE Science (Biology) ‘Infection and Immunity’ presentation for more information on antigens and the immune system.Before and after a transplant operation, a patient takes immunosuppressant drugs. These drugs inhibit the activity of the immune system.