Chapter 13.1- EXCRETION IN HUMANS IGCSE BIO
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The document discusses the excretion process in birds and reptiles, highlighting their efficient conversion of ammonia to uric acid, which is less water-intensive. It details the formation and excretion of urea in humans, with a focus on the role of the liver and kidneys, as well as the structure and function of the nephron. Additionally, it covers urine formation, the pathways it takes through the urinary system, and treatments for kidney failure such as dialysis and transplants.
Chapter 13.1- EXCRETION IN HUMANS IGCSE BIO
- 3. Have you ever had bird dropping land on you? Reptiles and birds Less water-wasting process for dealing with their bodies' ammonia Instead of ammonia to urea, they convert it to uric acid Excreted as a white paste or even a dry, white powder Through cloacae
- 4. Terms you should know Cortex Medulla Pelvis Urethra Urine Ureter Renal capsule Glomerulus nephrons Tubules Bladder Re-absorption Loops down Filtration Dialysis
- 5. 13.1 What is Excretion? The removal of metabolic waste products & excess substances ◦ CO2 is a waste of Respiration ◦ CO2 is toxic in large amounts Excretion ≠ Egestion ◦ The material in feces is not MWP’s; it was never digested or absorbed. Egestion ◦ Getting rid of undigested materials ◦ Ex Cellulose in feces
- 6. 13.1 Excretory Products Carbon Dioxide ◦ Produced by cell Respiration Urea ◦ Produced in Liver, removed by kidneys Water ◦ In excess, removed by kidneys
- 7. Nitrogenous Waste Animals produce Nitrogenous waste From excess proteins and amino acids Cannot stored, broken down into nitrogen-containing excretory products = Urea
- 9. How do you Produce Urea? Eat proteins Digested into amino acids and absorbed into your blood AA’s travel to the Liver via HPV Deamination ◦ Excess AA broken down ◦ Part of AA with energy – stored as glycogen ◦ The part with N will be excreted as Urea
- 12. Quick Review 1. You eat a protein and break it down into AA’s. Where do the AA’s go next? 2. What happens to extra AA’s in the Liver? 3. Where does the urea go next?
- 13. Answer 1. You eat a protein and break it down into AA’s. Where do the AA’s go next? To the Liver (thru the HPV) 2. What happens to extra AA’s in the Liver? They get deaminated and made into urea 3. Where does the urea go next? To the kidneys, then out of the body thru the ureters bladder urethra.
- 15. How do you Excrete Urea? Protein AA Urea Urea goes back into the blood - travels to the kidneys. Kidneys take urea out of the blood and mix it with water to make urine. The urine flows from the: kidneys 2 ureters bladder. Exit thru urethra.
- 16. URINE FORMATION Filtered as blood passes through kidneys Filters ◦ most urea, water, salt, glucose Reabsorbs ◦ All glucose, some salts, some water Final liquid product – urine
- 18. URINE FORMATION Filtered as blood passes through kidneys Filters ◦ most urea, water, salt, glucose Reabsorbs ◦ All glucose, some salts, some water Final liquid product – urine
- 20. Kidney Tubules Tiny units of tubules called nephrons ◦ Urea is filtered out of the blood ◦ Begins in the cortex ◦ Ends in the pelvis ◦ Cortex Medulla Cortex Medulla Pelvis Network of blood capillaries around the nephrons ◦ For reabsorption
- 22. FILTRATION ◦ Glomerulus Tangle of blood capillaries Blood vessels bring blood here to be filtered Towards = wide / Away = narrow Builds high pressure ◦ Renal capsule ◦ Water and dissolved substances squeezed out of blood into renal capsule ◦ Shaped like a cup ◦ Thousands in the cortex
- 24. REABSORPTION Useful substances reabsorbed back to the blood Remaining fluid(urine) is excreted Kidneys – very efficient ◦ 99% of water reabsorbed Kidneys filter 170 L of water per day Urine production in adults: 1-2 L per day
- 26. Bladder Urine from all tubules flow into ureters Ureters take it to bladder Stores urine temporarily Urethra ◦ Male: 18–20 cm long ◦ Female: 4–6 cm long Sphincter muscle ◦ at the top of urethra Full bladder - opens
- 29. Kidney Dialysis Dialysis unit Used for kidney failure Blood flows through machine and back into body Treatment – 2 or 3x a week Kidney Transplant Transplants successful as long as the blood type matches Rejection ◦ WBCs attack donor organ Immunosuppressant ◦ Decrease chances of rejection