Transcript Excretory System (Remee v1)

Excretory System
Function and Parts
Excretion
• Different organs in the body have roles for
the removal of waste products.
• The removal process is known as
EXCRETION.
• The excretory system is the system in the
body that collects wastes produced by cells
and removes the wastes from the body.
Why is excretion necessary?
• In order for cells to stay alive, they must
continually intake water and other molecules.
• The cells would continue to get bigger and bigger
if they only took in molecules
• They must also export molecules
– These molecules may be important signaling
molecules such as hormones, or they may be
molecules of glucose on their way to other cells, or
they may be waste products of cellular metabolism
that cells need to dispose.
The Excretory System
• The structures of the excretory system are:
–
–
–
–
Kidneys (2)
Ureters (2)
Urinary bladder
Urethra
The Excretory System
• The waste eliminated is
–Urea: a chemical that comes
from the breakdown of
proteins
–Water
The Job of the Kidneys
• They are responsible for cleaning the blood
by removing metabolic wastes and excess
water and excreting them as urine.
• Besides removing urea, it also removes
excess salts or glucose, the remnants of
drugs (reason for urine tests), and excess
water.
The Kidney
Nephrons
The kidneys are champion filters but the real workers
are the nephrons.
Each of your kidneys contains about
a million nephrons:
The tiny filtering factories that
actually remove the waste from
blood and produce the urine.
Formation of Urine
• If there is too much water in the blood, the
kidneys/nephrons will remove it and put in urine.
• If there is not enough water in the blood, the
kidneys/nephrons will not remove it.
• If there is too much urea or other liquids in the
blood, the kidneys/nephrons will remove these
too.
• By regulating the internal environment and
keeping if free of harmful levels of chemicals the
kidneys normally maintain homeostasis.
The Hard-working Kidneys
• The two kidneys in the body receive
between 1100 – 2000 liters (1160 – 2100
quarts or 500 gallons) of blood per day –
about the volume of a car!
• Because the body has only about 5.6 liters
of blood, your blood runs through the
kidneys to be cleaned about once every
four minutes.
Other Organs of Excretion
• The lungs: remove carbon dioxide and
excess water as water vapor when you
exhale.
• The skin: removes water and salt when
you sweat.
• The liver: removes wastes from the blood
– The liver works both excretory and digestion
making urea and bile.