Transcript kidney[1]
THE KIDNEY •T H E R O L E O F T H E K I D N E Y •D I S S E C T I N G T H E K I D N E Y LEARNING OUTCOMES • 1. recall that the lungs, kidneys and skin are organs of excretion (2.68) • 2. describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra (2.70) REVIEW QUESTIONS • The blood is to the circulatory system as ________ is to the lungs. • The _______ is to the circulatory system as lungs are to the respiratory system • Amino acids are to proteins as _______ are to carbohydrates ORGANS OF SECRETION: SKIN • • • • • Role of the skin: Protection against damage Preventing entry of disease Sense organ Controlling heat loss ORGANS OF EXCRETION: LUNGS • The lungs take in oxygen from the air and remove Carbon Dioxide (excretion) THE FUNCTION OF THE KIDNEY The kidneys are essentially blood filters. Blood is brought to the kidneys to be filtered by the renal artery. After filtering, the blood is taken away again by the renal vein. The kidneys have four functions: 1. Maintaining the water balance in the body by a process called OSMOREGULATION 2. Reabsorption of useful substances into the blood 3. Adjustment of the levels of salts and ions in the blood 4. Excretion of urea and other metabolic wastes Write this in the front of your books WATER BALANCE: • State three ways in which the body gains water and three ways in which the body loses water • What is the difference between the amount of water lost and the amount of water gained by the body? • Why is this important? What is maintained in the body by keeping this balance? KIDNEY LOCATION IN HUMAN • Two kidneys – each about the size of a fist, and lie at waist level at the back of the body. • Humans have two kidneys. They are beanshaped organs, approximately 11.5 cm long, situated in the abdominal cavity, just below the ribcage, one on either side of the spine. They are embedded in fatty tissue for protection. A CLOSER LOOK AT THE KIDNEY This is a human kidney. You have 2, but can survive with only 1. DIAGRAM OF THE KIDNEY • • • • A longitudinal section through a kidney shows three distinct areas: an outer region called the cortex a middle region called the medulla, and an inner region leading to the ureter, called the pelvis. DISSECTING A KIDNEY: WHAT TO LOOK FOR BLOOD SUPPLY TO KIDNEY • Renal artery supplies blood to kidney. • Renal vein takes blood away from kidney. • Ureter connects kidney to bladder • Urethra connects bladder to outside of body it is where urine leaves the body. EXCRETION OF UREA 1. Urea is a waste product from the breakdown of proteins. 2. If more protein is eaten than is needed the body will have an excess of amino acids, which cannot be stored by the body. 3. The excess amino acids are broken down by the liver, with urea as a by-product. 4. Urea is toxic, and must be excreted from the body, so it is passed into the blood to be filtered out by the kidneys. 5. It is then passed to the bladder for storage as urine, before leaving the body. Write this in the front of your books PRODUCTION OF URINE vena cava renal vein aorta renal artery cortex renal vein renal artery ureter kidney bladder pelvis medulla sphincter muscle urethra pyramid ureter HOW THE KIDNEYS WORK Blood enters the kidneys (renal artery) Millions of nephrons (mini-filtering systems) sieve the blood Needed substances are reabsorbed and the waste products are removed in the form of urine Clean blood returned to the blood (renal vein) Urine carried to the bladder by tubes called ureters When the bladder is full, urine passes out of the body via the urethra Structure of the nephron Ultra Filtration- all small molecules and lots of water Blood high in urea Blood low in urea Selective reabsorption- useful substances back into blood from tubules (water sugar ions) Excretion of waste- excess ions and water plus all urea as urine Urine to bladder WATER BALANCE • Our bodies control the amount of water in our blood and tissues through the endocrine system (hormonal system) • Like thermo-regulation, water balance is a negative feed back system that relies on the hypothalamus in the brain. • Anti Diuretic Hormone (ADH) is released in the blood to control how much water the kidneys release in urine. IF BODY HAS TO LITTLE WATER Sensor Hypathalmus detects low blood water concentration Response Pituatory gland produces more ADH Kidney reabsorbs more water into blood Result Less volume of urine produced (more concentrated IF BODY HAS TOO MUCH WATER Hypathalmus detects high blood water concentration Pituatory gland produces less ADH Kidney reabsorbs less water into blood higher volume of urine produced (less concentrated CONTROL OF WATER Pituitary gland produces less ADH Kidneys excrete more water in urine + water in blood hypothalamus - water in blood Pituitary gland produces more ADH Blood enters brain Kidneys excrete less water in urine WATER BALANCE • 1. 2. Healthy kidneys filter the blood to: Remove waste products (from metabolism of the food we eat and body cells). Remove excess fluid to balance fluid levels in the body AND FINALLY…… Homework; 1. Revise for module test 2. Visit http://www.bbc.co.uk/schools/gcse bitesize/biology/humansasorganisms /6homeostasisrev5.shtml. work your way through the section on kidneys and try the higher tier test.