Mammals

Excretory System

• To filter out and eliminate metabolic, nitrogenous wastes and help maintain homeostasis– Gets rid of excess H2O ,

salt, vitamins, toxins, minerals, and heat

– Nitrogenous Waste: cells create ammonia which the liver converts to urea (urea is the yellow color in urine)

Job:

Humans/Mammalian Excretory System:

• Lungs: – Eliminates CO2, excess

water and heat.

• Sweat glands: – Eliminates excess

water, heat and salt.

• Kidneys:– Eliminates nitrogeneous

waste, salt and water.

• 2 kidneys-reddish bean shaped organ– Size of a clenched fist– Lie along in small of

back

Excretory System

Structure of a nephron

• Each kidney is made up of one million+ nephrons (filtering unit)

• Blood enters kidney via the renal artery

• Blood is pushed through a nephron where excess H2O, salt, toxins, minerals, urea is filtered out.

Structure of a nephron

• Blood enters the bowman's capsule

• Capsule filled w/ glomerulus( ball of blood vessels)

• All substances are filtered out

• Cleaned blood reenters circulatory system via the renal vein.

Structure of a nephron

• Impurities travel along the renal tube which leads to center of kidney.

• Some items reenter blood; impurities empty into the renal pelvis

3 Main Parts of a Kidney

• 3-parts– Cortex-outer

portion of kidney

– Medulla-inner region

– Renal pelvis-hollowed out area where all waste gathers.

Urine Formation

• All nephrons empty into renal pelvis

• Renal pelvis empties into the ureter(1/kidney)

• Ureter leads to bladder• Water and impurities

that collect in our bladder make up our urine which exits out the urethra

Urine Formation

• Average Adult:– ~1.5-2.3 Liters/day– Greatest amount of water loss

• Must urinate 500mL to get rid of toxins

Nonfunctioning Kidneys

Skin weighs 9 lbs!!!

Muscle Mass:

-1/2 Men

-1/4 Women

1 month to replace ALL skin cells