3. Human Excretion Excretion – process of removing waste substances produce by the metabolic processes from the body. Waste substance left in the body and not removed will become toxic and poison. Excretory organs – skin, lungs, kidneys Excretory substances – water, carbon dioxide, urea, excess mineral salts.

4. Human Excretion (cont’d)

5. Importance of excretion Disposal of toxic or poisonous substances e.g urea Disposal of excess subtances e.g salts and water

6. Urinary system

8. Urinary system (cont’d) Human kidney Dark red, broad bean-shaped organ Located at the back of the abdomen Parts : Cortex – lighter outer region Medulla – darker inner region Pelvis – central cavity Ureter – connects the pelvis to the bladder

9. Urinary system (cont’d) Function of the kidneys 1. Remove nitrogenous waste products e.g urea 2. Balance the water and mineral contents 3. Maintain the pH of the blood and tissue fluid

10. Urinary system (cont’d) Ways to maintaining healthy kidneys: Taking urine and blood test Limit protein and salt intake Maintaining blood sugar control (for diabetics) Drink, at least 8 glass of water per day Learn about symptoms of kidney failure

12. Urinary system (cont’d) Living with kidney failure Human can survive with one healthy kidney Cause of kidney failure : 1. Bacterial infection 2. Injury 3. High blood pressure Two ways to treat kidney failure 1. Haemodialysis 2. Kidney transplant

14. Urinary system (cont’d) Haemodialysis Dialysis machine works in similar to kidney Blood is withdrawn and circulated through the machine Blood flows through a dialysis tube, surrounded by dialysing solution

15. Urinary system (cont’d) Haemodialysis (cont’d) Urea and excess salts diffuse into the dialysing solution Used dialysing solution is discarded

16. Urinary system (cont’d) Kidney transplant The kidney of donor should be match to the patient

17. Excretion in plants Plants produce relatively small amount of waste products. less active – accumulate waste slowly Do not have specialised excretory organs

18. Excretion in plants (cont’d) Excretory productsSourceMethod of exrection Carbon dioxideRespiration Diffuse through stomata OxygenPhotosynthesis Diffuse through stomata WaterPhotosynthesis Transpiration Some other waste products Latex, resins, gum Stored in plants and released when the plants die and decay Some are useful to humans Latex – manufacturing Resins – paint industry