Download Chapter 38: Excretory System

Chapter 38:
Excretory System
Functions of the Excretory System
a. Collect water and filter body fluids
b. Remove and concentrate waste products from body fluids
and return other substances to body fluids as necessary for
homeostasis
c. Eliminate excretory products from the body
- Include the kidneys (removes the most metabolic waste
via urine),liver, lungs, and skin
*** Responsible for regulating water balance in various body
fluids
- Osmoregulation is the active regulation of the osmotic
pressure of an organism's fluids to maintain the
homeostasis of the organism's water content; that is it
keeps the organism's fluids from becoming too dilute or too
concentrated (balance b/w sodium & water)
ANIMAL EXCRETORY STRUCTURES
• PROTOZOA: CELL MEMBRANE
(DIFFUSION) CONTRACTILE
VACUOLE (EXCESS WATER)
• FLATWORM(PLANARIA):
FLAME CELLS
• EARTHWORM: NEPHRIDIA,
SKIN
• GRASSHOPPER: MALPHIGIAN
TUBULES, TRACHEAE
• CRAYFISH: KIDNEYS, GILLS
• HUMAN: LUNGS, SKIN, LIVER,
KIDNEYS
• SNAKE: KIDNEYS
ANIMAL EXCRETORY STRUCTURES
• Made-up of the kidneys,
ureters, bladder, and
urethra.
• Nephron, an
evolutionary modification
of the nephridium the
kidney's functional unit
• Waste is filtered from the
blood and collected as
urine in each kidney
• Urine leaves the kidneys
by ureters, and collects in
the bladder can distend
to store urine that
eventually leaves through
the urethra
• Renal artery brings blood into kidneys
• Renal vein takes blood back to heart
Nephron- Urine Production
Urine Production
1. Filtration in the glomerulus and nephron capsule
2. Reabsorption in the proximal tubule
3. Tubular secretion in the Loop of Henle
Components of The Nephron
a. Glomerulus: mechanically filters blood
b. Bowman's Capsule: mechanically filters blood
c. Proximal Convoluted Tubule: reabsorbs 75% of the water,
salts, glucose, and amino acids
d. Loop of Henle: countercurrent exchange, which
maintains the concentration gradient
e. Distal Convoluted Tubule: tubular secretion of H ions,
potassium, and certain drugs
Section 38-3
Structure of the Kidneys
Kidney
Nephron
Bowman’s
capsule
Cortex
Capillaries
Glomerulus
Medulla
Renal artery
Renal vein
Ureter
Collecting
duct
Vein
To the bladder
Artery
Loop of Henle
To the ureter
Section 38-3
The Nephron
Reabsorption
Filtration
Most filtration occurs in the
glomerulus. Blood pressure forces
water, salt, glucose, amino acids, and
urea into Bowman’s capsule. Proteins
and blood cells are too large to cross
the membrane; they remain in the
blood. The fluid that enters the renal
tubules is called the filtrate.
As the filtrate flows through the renal
tubule, most of the water and
nutrients are reabsorbed into the
blood. The concentrated fluid that
remains is called urine.
KANGAROO RAT – LIVE IN HYPERTONIC
ENVIRONMENT
ADAPTATIONS
• VERY EFFICIENT KIDNEYS, WHICH
ALLOW IT TO LIVE WITHOUT
DRINKING!
• HAVE A LONGER LOOP OF HENLE IN
THEIR NEPHRONS, CAUSING THEM TO
PRODUCE URINE THAT IS 5 TIMES
MORE CONCENTRATED THAN
HUMANS
• DON’T SWEAT, AND LOSE WATER ONLY
THROUGH EVAPORATION DURING
GAS EXCHANGE
• RETAIN 90% OF THEIR WATER, AND
10% COMES FROM THEIR DIET