Download The Excretory System

The Excretory System
Elimination of wastes
How do organisms get rid of wastes???
Bacteria – diffusion
 Protists – diffusion
 Fungi – diffusion
 Plants – diffusion through stomata

Sponges & Cnidarians
Diffusion
Flatworms
Diffusion for most waste
 “Flame cells” help with waste removal and
water level control

Roundworms

Excretory tube collects waste and sends to
the outside
Segmented Worms & Mollusks

Have 2 nephridia per segment that
remove waste from body fluid. Waste
moves though tubes and leaves through a
pore
Arthropods
Malphigian Tubules – remove
nitrogenous waste from blood and nearby
tissues
 Digestive waste – Moves through
digestive pathway and is exits through
rectum

Echinoderms

Wastes move into water vascular
system and exit through the anus on top
Fish & Amphibians



Undigested food exits the body through the
cloaca
2 Kidneys filter waste from the blood
Gills
Reptiles & Birds

Kidneys and excretory pathway are
similar to fish and amphibians, except
reptiles and birds excrete uric acid in a
thick pasty material to conserve water!
Mammals

Have 2 kidneys that filter waste from the
blood every 45 mins
II. Human Excretory System
A. Function – removes wastes, such as urea,
from the body
B. Excretory organs
1. Kidneys – (2) remove waste and
extra salts, drugs, sugars, and water from
the blood
a. contains many nephrons –
filtering units
B. Excretory organs
(continued)
2. Ureters – 2 tubes that carry wastes
from each kidney to the bladder
3. Bladder – temporary storage of
urine
4. Urethra – empties urine from body
The Urinary System
Section 38-3
Vein
Kidney (Cross
Section)
Kidney
Cortex
Medulla
Ureter
Urinary bladder
Urethra
Artery
Figure 38-17 Structure of the Kidneys
Section 38-3
Kidney
Nephron
Bowman’s
capsule
Cortex
Medulla
Renal
artery
Capillaries
Glomerulus
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.
Section 38-3
Figure 38-19 Kidney Dialysis
Blood in tubing flows
through dialysis fluid
Blood pump
Vein
Artery
Used dialysis fluid
Shunt
Air detector
Dialysis
machine
Fresh
dialysis
fluid
Compressed
air