The Excretory System

What is Excretion?

• Excretion – the process of removing wastes from the body.– Can be in the form of a solid, liquid or gas.

• Wastes are useless to the body but if left to build up inside a person they could become poisonous and result in illness or death.

Types of Wastes• Solid Wastes:

– Indigestible material left after digestion and absorption – feces.

• Discussed during Digestive System

• Gaseous Wastes:– The carbon dioxide you exhale.

• Discussed during Respiratory System

• Liquid Wastes:– Excreted from the body as either urine or sweat.

• Both are more than 90% water.– Contains waste nitrogen and salts.

The Urinary SystemKidneys

Ureter

UrinaryBladder

Urethra

Organs of the Urinary System1. The Kidneys• We have two kidneys

– Unfiltered blood enters through the renal artery off the aorta.

– Filtered blood leaves through the renal vein.

• Function:– Filter blood– Remove water and salts.– Make urine for

excretion.

RenalArtery

RenalVein

Ureter

UrinaryBladder

Parts of the Kidney• Nephrons – filter the

blood to produce urine.– Approximately 1 million

per kidney.– Located in the outer rim of

the kidney.– Looks like a long coiled

tube with a cup at one end.• Each tiny tube extends into

the center of the kidney.

Nephron Artery Vein

Ureter

To the Urinary Bladder

Parts of the Kidney• Glomerulus – A ball of

capillaries surrounded by the nephrons.– Particles being filtered

out; salts, amino acids, water, glucose and urea of the blood pass into the glomerulus.

• Harmful wastes continue down into the tubule.

• Beneficial products, water and some salts are reabsorbed.

GlomerulusTubule

Organs of the Urinary System2. The Ureter• Ducts that carry urine from

the kidneys to the urinary bladder.

3. Urinary Bladder• Stores the urine until it is

released from the body.

4. Urethra• Opening through which

urine leaves the body.

RenalArtery

RenalVein

Ureter

UrinaryBladder

Urine• Yellowish in color

– Dehydrated = darker yellow• Less water and higher concentration of salts and metabolic

wastes.• Body purposely reabsorbs as much water as it can to keep

functioning.– Hydrated = pale yellow to clear

• An excess of water that is not needed by the body and contains fewer metabolic wastes.

• Make-up:– 95% water– 5% dissolved particles (salts and metabolic wastes)

Kidney Stones: 1:53min

Kidney Stones

Other Excretory Organs

1. The Liver• Also filters the blood

as it passes through it.– Absorbs drugs and

other poisonous chemicals

• Changes their chemical structure.

• Excreted in the bile.

• Largest internal organ of the body!

Gall Bladder

Liver

Other Excretory Organs2. The Skin• The largest organ of the

human body.• Functions:

– Excretion - water, salt, urea and uric acid are removed in sweat.

– Waterproofing - oil glands prevent entry of water into, and loss of water out of the body.

– Protection from Disease – Regulation of Body

Temperature – Sensory Detection - heat,

cold, touch, pressure and pain.

Epidermis

Dermis

Fat Cells

Other Excretory Organs• 2 layers:

– Epidermis – outer layer• Provides a waterproof,

protective wrap over the body.

• Contains NO blood vessels.

Epidermis

Dermis

Fat Cells

Other Excretory Organs– Dermis – inner layer

• Rich in blood vessels• Also contains hair

follicles, sweat glands, and oil glands.

Epidermis

Dermis

Fat Cells

Hair FollicleOil Gland

Sweat Gland

Sweating

• Also called Perspiration• Primary means of temperature regulation:

– sweat cools the body due to evaporation.• Causes of sweating:

– Too hot, stressed or nervous • What is sweat?

– Water, salts, urea.

• BrainPop – Excretory System