Chapter 19
Excretion
in
Humans
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Excretion
™The
removal of metabolic
wastes from an organism
(I) Human Excretory Organs
Lungs
Liver
Skin
Lungs
™Rid
the body of CO2 and excess
H2O from the blood during
exhalation (breathing out)
Liver
™ Largest
internal organ
™ Major function is the removal of
toxins (poisons) from the blood.
This process is know as
detoxification and therefore, the
liver helps in purifying the blood
™ Produces bile which is used for the
breakdown of fats (emulsification) in
the small intestine
Liver
A)
detoxification- removal of toxins
from the blood
B)
Urea- is formed in the liver from
the breakdown of amino acids in a
process known as Deamination
-urea then diffuses into the blood
and is transported to the kidneys
and excreted in the form of urine
Urinary System
™A
group of organs whose sole
purpose is to perform excretion
™The urinary system consists of:
Kidneys
Ureters
Urinary bladder
Urethra
Urinary System
Urinary System
Kidneys
™ Bean-shaped
organs located below
and toward the back of the
diaphragm
™ Perform two major functions:
1. Remove wastes from blood
2. Controls the concentration of
various substances in the body
™ The functional units of the kidneys
are known as nephrons
Kidney
Nephrons
™Each
kidney contains
approximately 1.25 million
nephrons
™The nephron begins with a
cluster of capillaries called the
glomerulus
™The glomerulus is surrounded by
a cup-like structure called
Bowman’s capsule
Nephron
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The way the nephron works:
1.
2.
3.
Blood is carried to each kidney by the
Renal artery
The renal artery subdivides into smaller
arterioles and then subdivides into a ball
of capillaries known as the glomerulus
Each glomerulus is part of the nephron
4. Through diffusion (passive
transport), wastes are filtered out
(urea, water, and salt) and enter the
Bowman’s capsule
5. From the Bowman’s capsule, the
filtrate (waste) passes through a long
tubule surrounded by capillaries
6. Through active transport, useful
substances are reabsorbed into the
capillaries from the Loop of Henle
7. The remaining liquid, called urine,
pass into the collecting tubule and
then pass out of the kidney and into
the ureter
8. Urine is composed of urea, water,
and salt
9. Urine then travels down the ureter,
into the urinary bladder, and out of
the body through the urethra
Ureter
™Structure
that carries urine from
the kidneys and into the urinary
bladder
Urinary Bladder
™Temporarily
store urine
Urethra
™Urine
is excreted from the
bladder, through the urethra and
out of the body
Skin
™Largest
external organ of the
body
™In contact with the external
environment
™Composed of two layers:
epidermis
dermis
Skin Cross-section
™ Epidermis-
outer
layer of the skin
used for protection
™ Dermis- lower
layer of the skin
where sweat glands
are found
Sweat Glands
™ Consist
of tiny coiled tubes that
open to the surface of the skin
through pores
™ Perspiration (sweat) is excreted
by these glands
™ Perspiration consists mostly of
water (98%), salts, and urea
Function of Skin
1.
2.
3.
4.
Protects internal tissue of the body from injury
and the entrance of foreign materials and
microorganisms
Excretes a small amount of urea and salt in the
form of perspiration
Nerve endings in the skin detects stimuli like
heat, and pain
The skin is also involved in the regulation of
body temperature (homeostasis)
- sweating cools the body
Skin
™Sweat
glands secrete wastes in
the form of water, urea, and salt
(perspiration)
™These wastes pass by diffusion
from capillaries and into sweat
glands and then through ducts
that transport the waste to the
pores in the surface of the skin
A Closer look
at the
Liver and Skin
(III) Diseases of the Excretory
System
™Diseases
of the kidneys affects the
ability of the body to eliminate
normal amounts of metabolic
wastes
Gout
™Produces
symptoms similar to
arthritis
™Caused by deposits of uric acid in
the joints
™Victims of gout suffer severe pain
and stiffness in the joints