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EXCRETION
Functions
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Removal of metabolic wastes from the body
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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)
⬜
Main Organs Involved in
Excretion
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Lungs – remove carbon dioxide
from the body through
respiration
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Skin – removes urea, salt, and
excess water through sweat
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Kidneys – remove urine (urea,
salt, and excess water) through
filtration and urination
Skin
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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
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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
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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
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Capillaries
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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
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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
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Nephron
◻
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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
Ureter
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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
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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
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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
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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