According to the 2010 syllabus
- Define excretion as the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements. Substances should include carbondioxide, urea and salts.- Outline the structure of a kidney (cortex,medulla, and the start of the ureter) and outline the structure and functioning of a kidney tubule
including:
• role of renal capsule in filtration from blood of water, glucose, urea and salts
• role of tubule in reabsorption of glucose,most of the water and some salts back into the blood, leading to concentration of urea in the urine as well as loss of excess water and salts((abut the structure i had sum notes but i seriously cant find it.....rly searched a lot))
- Describe the function of the kidney in terms of the removal of urea and excess water and the reabsorption of glucose and some salt(details of kidney structure and nephron are not required)Function Of The Kidney-
The function of the kidney is to filter blood,removing urea and excess water but reabsorbing glucose, some water and some mineral salts. The liquid produced is called urine - a solution of urea and mineral salts in water. The kidneys recieve blood from the aorta(the main artery) via renal arteries. The renal artery spilts into millions of capillaries, from which the blood is filtered under pressure. This forces all the small molecules and ions(such as glucose,urea,water and mineral salts) out of the capillary into a nephron. As the filtrate passes thru the nephron , reabsorption takes place. Water is reabsorbed by osmosis, while glucose and mineral salts pass bck into the blood by diffusion and active uptake. The relative amount of water reabsorbed depends on the state of hydration of the body (how much water is in the blood), and is controlled by secretion of the hormone ADH. On a hot day,when we sweat more to cool down, the body needs to conserve water so we tend to produce a small amount of concentrated urine. On a cold day little sweat is being produced, so we tend to produce a larger volume of dilute urine. Filtered blood returns to the vena cava(main vein) via a renal vein.
The urine formed in the kidney passes down a ureter into the bladder, where it is stored. A sphincter muscle controls the release of urine thru the urethra.
- State the relative positions of ureters, bladder and urethra in the body.http://www.comprehensive-kidney-facts.com/images/ExcretorySystem.gifhttp://mypages.iit.edu/~smart/sheajan1/60.gifhttp://kvhs.nbed.nb.ca/gallant/biology/excretory_anatomy.jpghttp://2.bp.blogspot.com/_JQoYdcg50hk/R75-sBQp0_I/AAAAAAAAAD8/e07wdhvUtro/s400/urine+excretory+system.JPG-State that urea is formed in the liver from excess amino acids
- State that alcohol, drugs and hormones are broken down in the liver
- Explain dialysis in terms of maintenance of glucose and protein concentration in blood and
diffusion of urea from blood to dialysis fluid
- Discuss the application of dialysis in kidney machinesDialysis is a method of removing one or more components from a solution using the process of diffusion. The solution is separated from a bathing liquid by a partially permeable membrane (made of cellulose). The bathing liquid contains none of the componenets that need to be removed from the solution , so these pass from the solution, through the membrane, into the bathing solution by diffusion. The bathing solution needs to be changed regularly to maintain a concentration gradient.
http://www.londonderrynh.net/wp-content/uploads/2009/06/20090616_kidney_dialysis.jpgA patient with kidney failure needs to have toxic chemicals removed from the blood to stay alive.Blood is is removed from a vein in the arm,and is kept moving through dialysis tubing in the dialysis machine using a pump.The tubing is very long to provide a large surface area.The dialysis fluid has a composition similar to blood plasma,but with no urea or uric acid.Urea, uric acid and excess mineral salts are removed from the blood by diffusion into the dailysis fluid. The cleaned blood is then passed t
hrough a bubble trap to remove any air bubbles before being returned to the patient's vein.
- Discuss the advantages and disadvantages of kidney transplants, compared with dialysisAdvantages-
- The patient can return to a normal lifestyle- dialysis may require a lenghty session in hospital, three times a week, leaving the patient very tired after each session
- A dialysis machine will be available for other patients to use
- Dialysis machine are expensive to buy and maintain
Disadvantage-
- Transplant requires a suitable donor - with a good tisue match.
- The operation is very expensive
- There is a risk of rejection of the donoted kidney
http://www.youtube.com/watch?v=chhNaLi9P3E&feature=relatedhttp://www.youtube.com/watch?v=4-15JUVxAm8&feature=relatedhttp://www.youtube.com/watch?v=TzwPmz5V6Xg&feature=relatedThe notes are from this IGCSE study guide
Hope it helps
