EXCRETION

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)

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

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

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)

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.

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

Sweat Glands Sweat glands are located all over the skin except on lips. 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

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

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

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

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

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

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

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

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

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

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