1. EXCRETION

2. Metabolism and Excretion
Metabolism-is the sum total of all reactions going on in cells. Waste -the reactions of metabolism produce a range of waste called excretory products, which the body needs to get rid of. Excretion- is the process by which excretory products which are made in the cells are removed

3. Excretion is not to be confused with…..
Egestion- the removal of undigested food from the gut. By….. Defecation- this is the removal of faeces during egestion Secretion- which is the release of a substance, such as a hormone from the cells

4. Excretory products in animals (1
Excretory products in animals (1.waste products due to respiration in the cells)
What are some of the waste products of respiration? Carbon dioxide- this is dangerous to living tissue because it increases the acidity of fluids which can affect other reactions. In man CO2 is transported to the lungs where it is exhaled Heat- is also given off during respiration, it can accumulate and increase the body temperature. At high temperatures enzymes can be denatured. Excess heat is lost through the skin

5. Excretory products in animals (2.Waste products from red blood cell)
Red blood cells have a short life span (~ 3 months) and are destroyed in the liver or spleen. The haemoglobin contain 3 parts i) the protein part which is broken down it amino acids and reused ii) iron- which is extracted, stored or used iii) the remainder is broken down by bile pigment and excreted by the gut, out the feaces

6. Excretory products in animals (3.Waste products of protein metabolism)
Proteins contain nitrogen, so the breakdown of protein produces nitrogenous waste which is converted to urea. This excretory nitrogenous waste; urea is removed by the kidney during the production of urine

7. Excretion in plants (the excretory products of plants)
What are the products of photosynthesis? What is needed by the plant? What are the waste products How are these removed? O2- (photosynthesis) ,excess diffuses out of the stomata CO2 - (respiration),excess diffuses out stomata H2O- ( respiration)is either needed by the plant or lost in transpiration. Heat -( respiration), excess diffuses out of the stomata Calcium oxalate and Tannins - ( from metabolic processes)these and other insoluble waste products are stored in leaves, bark, flowers fruit and seeds. Lost in leaf fall.

8. The human excretory system The kidneys
The kidneys are the major excretory and osmoregulatory organs of mammals
Osmoregulation- is the control of the amount of water in the blood

10. Keys points to remember about the kidney
The renal artery brings blood with nitrogenous waste
The cleansed blood returns to the heart via the renal vein
This waste is stored in the bladder(urine)
The kidney is made up of 3 regions
i) cortex
ii) medulla
iii) pelvis
Each kidney is made up of thousands of structures called nephrons

11. A longitudinal section through a kidney

12. The nephron The keys regions of the nephron are:
arteriole
Bowmans capsule
Loop of henle
Distal convoluting tubule
Proximal convulting tube
Collecting duct
glomerulus
Cortex
medulla

15. Pressure filtration
What is responsible for the smaller components of the blood being pushed out into the surrounding bowman’s capsule?
What are the components of the filtrate?
What are large molecules which remain in the blood?

16. Selective reabsorption of glucose
Selective reabsorption- this is the preferencial reabsorption of a substanceover other.
Where in the nephron does selective reabsorption of glucose occur?
Glucose in the filtrate is selectively reabsorbed by the capillaries that surround tubules

17. Reabsorption of water
This occur in the loop of henle, the longer the loop of henle the more water is reabsorbed by the capillaries

18. Distal convoluting tubule
What occurs here?
Urine
The filtrate that remain after the distal convoluting tubule is called urine. It contians water, salts and urea. The urine flows into the pelvis of the kidney the thousands of collectiing ducts, it then flow via the ureter to the bladder to be stored before urination

19. HOMEWORK
DO QUESTIONS 1 to 3 ON PAGE 139 in your textbook. Homework is to be submitted on folder paper or foolscap at the beginning of the next class on Thursday morning.