2Water & WasteGetting rid of poisonous wastes and regulating the amount of water in the body are two important processes that occur in animals.If they are not performed correctly then the animal may die.The kidneys deal with both of these processes.
3Our bodies gain weight in three different ways. Water GainOur bodies gain weight in three different ways.DrinkingIn a typical day we drink a variety of liquids e.g. tea, coffee, milk, etc…. All of these liquids consist mainly of water.
4Water Gain Water from food. Water from chemical reactions. All the foods we eat contain different amounts of water.Water from chemical reactions.The food we eat is used up by the cells of the body to supply energy and materials for growth and repair. The chemical reactions that release the energy from food also produce water.
5Our bodies lose weight in four different ways. Water LossOur bodies lose weight in four different ways.Sweat.Our skin produces sweat in order to cool the body down. The hotter we are the more sweat we produce.Breath.The air we breathe in may be dry or moist depending on the weather. The air we breathe out is always moist.Cobalt chloride paper is used to test for water. It turns from blue to pink.
6Water Loss Urine. Faeces. We get rid of excess water and waste products such as urea and some salts in our urine. Urine is about.96% water.2% urea.2% minerals.Faeces.Our faeces are moist so that they can be passed out of the body easily.Water balance exercises. Sheets 5A, 5B and 6.
7The Kidneys The kidneys have 2 main functions. Maintaining water balance.Getting rid of poisonous waste substances from the body.
9The KidneysIn humans the kidneys are solid, oval shaped structures found towards the back of the body below the ribcage.Blood enters the kidneys through the renal artery and leaves through the renal vein.The blood contains useful substances like glucose and a poisonous waste called urea.
10Testing for Glucose & Urea Test samples of blood from the renal artery and renal vein for both glucose and urea.Test samples of urine for both glucose and urea.SampleUrea present?Glucose present?Renal arteryRenal veinUrineFollow instructions on sheet G5.
11The Kidneys Blood entering the kidneys is filtered. This removes water containing harmful urea and useful glucose.Reabsorption is another process in the kidneys which takes back glucose and some of the water into the blood.This leaves behind the urea and the rest of the water.The amount of water reabsorbed depends on the body’s requirements.
12Water RegulationThe kidneys regulate water, but this regulation is under control from the brain.The brain produces ANTI-DIURETIC HORMONE (A.D.H.) which controls the amount of water reabsorbed by the kidney nephrons.Different amounts of ADH are produced to suit the varying water conditions of the body, ensuring water balance is maintained.ADH is one of a group of chemicals called HORMONES.Use worksheet C1 and the following statements.“Drinking”“Brain produces more ADH”“Water content in blood low”“Low volume of water reabsorption by kidney”“Low volume of concentrated urine”“High volume of dilute urine”
13Role of ADH Water content of blood too low Water content of blood too highSalt eaten or much sweatingToo much water drunkWater content of blood normalBrain releases little ADHBrain releases much ADHHigh volume of water passes into bloodLow volume of water passes into bloodHigh volume of water reabsorbed by kidneyLow volume of water reabsorbed by kidneySmall volume of concentrated urine passed to the bladderHigh volume of dilute urine passed to the bladder
14How the Kidneys WorkTo explain filtration and reabsorption we have to look at the detailed structure of the kidney.Each kidney is made up of about 1 million tiny tubes called NEPHRONS which filter the blood and then reabsorb the useful substances.
15How the Kidneys WorkWe know that proteins are broken down to amino acids in digestion.These amino acids are used to build new cells or repair tissues within the body.Any extra amino acids not needed at the time are broken down in the liver to a carbohydrate and a poisonous waste called urea.
16How the Kidneys WorkThe urea is then transported by the blood to the kidney where it is removed.If, due to kidney damage, the urea is not removed from the blood its level will build up and eventually cause death.
18When Kidneys go WrongIf the kidneys stop working because of disease or damage, then the person will die.This is known as total kidney failure.Sometimes kidney stones form in the kidneys. This condition is not usually fatal but can be very painful, and occasionally blockages may occur in the kidney.
19When Kidneys go WrongThese stones can usually be removed by operation and the patient recovers.If, however, total kidney failure occurs then this must be treated in one of two ways or the patient will die.dialysis on a kidney machine (artificial kidney)Kidney transplant
20Sugar DiabetesThis is a common disease which in 1987 affected 600,000 people in the U.K.It is caused by the inability of the body to deal with glucose in the blood.This results in too much glucose in the blood and can be very serious to the patient.When the blood passes through the kidney, much of this extra glucose can’t be reabsorbed and so is found passed out in the urine.