Excretion

1. Excretion Not of feces!!!

2. Functions • Removal of metabolic wastes from the body • Metabolic wastes are wastes that our cells have created through chemical reactions (EX: Cellular Respiration creates carbon dioxide that we need to get rid of) • Main wastes our excretory system removes: • Carbon Dioxide • Excess Water (too much water will disrupt osmosis) • Salt (will disrupt diffusion) • Heat (so our enzymes function properly) • Urea (created when we digest proteins, toxic)

3. Main Organs Involved in Excretion • Lungs – remove carbon dioxide from the body through respiration • Skin – removes urea, salt, and excess water through sweat • Kidneys – remove urine (urea, salt, and excess water) through filtration and urination

4. Skin • The skin has two layers • Dermis – lower layer of skin that is made up of cells, sweat glands, sebaceous glands, blood vessels and nerves • Epidermis – upper layer of skin covered in dead skin cells and live replicating cells below those

5. Epidermis • Functions: • Prevent Water Loss • Prevent absorption of unwanted materials • Protect cells contained by the skin • Keep dividing to keep up with the number of cells lost via friction (your skin touching other things)

6. Epidermis • Epidermis has four layers • Stratum corneum – top most layer composed of dead skin cells that protect the cells below it • Stratum granulosum – this layer of cells is about to die and become the next layer. The cells are full of granules that will keratinize to offer our skin the protection it needs • Stratum spinosum – This layer is full of lipids that reduce water loss from the skin • Stratum basale – the cells in this layer are constantly dividing to provide the above layers with new cells.

7. Dermis • Functions: • Cool the body • Send sensory information about pressure and heat

8. Sweat Glands • Sweat glands are located all over the skin except on lips and nipples. • They are essentially a ball of tubing which straightens and extend to the surface of the skin creating a pore • The purpose of the sweat gland it to cool the body when it is too hot • Some sweat glands excrete an odor as well as sweat. These are mostly concentrated in the arm pits and genital region

9. Capillaries • The capillaries in the dermis supply the sweat gland with the fluid and wastes to make sweat • The provide oxygen and nutrients to the dividing cells in the basal layer of skin cells and to the nerves and hair follicles in the dermis

10. Hair Follicles • A sac of cells that creates hair and which the sebaceous (oil) gland is connected • The base that is enriched with capillaries is the only living part of the hair • Hair is important because it is attached to nerves which send sensory information about how the hair moves • It also helps prevent air from stealing our warmth

11. Nerves • Sense pressure and hot or cold • Well you’ll just have to wait until the next unit to find out how that works

12. Urinary System 1. 2. 3. 4. 5. 6. 7.

13. Kidneys • A large artery called the renal artery flows into the kidney and divides into tiny capillaries • The capillaries join nephrons which makes up the kidneys where wastes such as urea and salt are filtered out • Then the newly filtered blood leaves through the renal vain to travel back to the heart • The waste materials flow into the ureter • The inner portion of the kidney is the medula and the outer layer is the cortex

14. Nephron • The capillaries form a ball called the glomerulus which is surrounded by the Bowman’s capsule • The Bowman’s Capsule thins out and forms a loop (Loop of Henle) • The capillaries go around the loop and as the loop descends the concentration changes pulling more urea out of the blood via diffusion

15. Ureter • The wastes (salt and urea) pulled from the blood by the Loop of Henle travel to the collecting duct, which leads to the Ureter • The ureter is the tube that urine (composed of urea, salt, and water) travels down from the kidneys to the bladder

16. Urinary Bladder • The bladder is a large muscular sac that holds the urine until there is enough to pass out of the body • The bladder is flexible and expands with increasing urine and contracts to push the urine out of the body through the urethra

17. Urethra • This is the tube that connects the bladder to the outside of the body • In men it has a smaller diameter and is much longer than in women

18. Excretory Diseases • Kidney stones – build up of minerals inside the kidneys until those minerals form a stone • Urinary Tract Infections – bacterial infection of the urethra and bladder causing irritation and bleeding • Kidney Disease – when the nephrons in the kidney start to die and stop filtering the blood (dialysis) • Gout – a build up of uric acid in the blood • Boils – a bacterial infection of the sweat gland causing it to swell and become very uncomfortable