1. Excretion Definition Kidney structure & function
Nephron structure and function
Urine production
Excretion

2. What is Excretion?
Excretion is the process by which metabolic waste and harmful substances are removed from the body.
These wastes are produced by chemical reactions occurring inside body cells (metabolism)

4. Products excreted by plants and animals
PROCESS BY WHICH PRODUCED
PROCESS BY WHICH REMOVED
Excess carbon dioxide
Respiration in cells
Diffusion via stomata
Excess oxygen
Photosynthesis in green plants
Calcium oxalate
Metabolism in cells
Stored as insoluble crystals in tree barks, aging leaves, flowers, seeds/fruits
Water
Respiration
Transpiration
ANIMALS
Carbon dioxide
Exhalation (lung expiration)
Respiration and external intake
Excretion (Kidneys) ( lungs) (skin)
Excess salts
Metabolisms and intake
Excretion
Urea
Deamination of amino acids
Heat
Metabolism

5. How do plants excrete?
Plants do not have any specialized excretory organ
Oxygen, carbon dioxide and water vapour diffuse out through the stomata
Organic waste products can be stored in dead permanent tissue eg, heart wood.
Organic waste can also be converted to insoluble substances such as oils and crystals.
These substances are stored in leaves, barks, fruits, seeds, petals and are removed when the plants shed these structures.

6. EXCRETION IN PLANTS

7. EXCRETION IN PLANTS

8. EXCRETION THROUGH STOMATA

9. OTHER EXCRETORY PRODUCTS

10. EXCRETION IN HUMAN
Humans have several organs that excrete waste products
The kidneys – excrete water, nitrogenous waste (mainly urea) and salts as urine
The lungs – excrete carbon dioxide and water vapour during exhalation
The skin – excretes water, urea, and salts as sweat. The skin also excretes heat
The liver – excretes bile pigments. The liver makes nitrogenous wastes

11. The kidneys

12. EXCRETORY Functions of the kidney
REGULATING:
body fluids
Blood pressure
Filtration of waste
Reabsorption of water

13. The kidney – (nephron)

15. The nephron – urine production

16. Urine production- Ultra-filtration
Occurs in the glomerulus
The diameter of the capillary entering the glomerulus decreases- this creates more pressure.
The pressure of the blood increases- this forces small molecules from the blood into the Bowman’s capsule
This now forms a filtrate.
The filtrate contains:
Glucose
Amino acids
Hormones
Vitamins
Salts
Urea
Larger molecules, for example, Plasma proteins remain in the blood

17. Urine production- selective reabsorption
Occurs in the nephrons
Useful substances are reabsorbed from the filtrate back into the blood
The reabsorbed substances travel through the capillaries that are wrapped around the nephrons
The substances reabsorbed:
Glucose, Amino acids, Hormones, Vitamins, Salts, Urea – reabsorbed in the proximal convoluted tubule
Some water – reabsorbed in the loop of Henle
Some salts and some water- reabsorbed in the distal convoluted tubule
NB// WATER IS REABSORBED BY THE PROCESS OF OSMOSIS
THE OTHER SUBSTANCES ARE REABSORBED BY DIFFUSION AND ACTIVE TRANSPORT
Larger molecules, for example, Plasma proteins remain in the blood

18. Urine production- filtration & secretion
Filtrate containing urea, excess water and excess salts enters the collecting ducts
Some water is reabsorbed in the collecting ducts by osmosis
The filtrate is now called urine
The urine travels down the collecting ducts to the ureter then to the bladder
The bladder stores the urine until it is ready to be released through the urethra.