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1. 32.4 Excretory System
KEY CONCEPT
The excretory system removes wastes and helps
maintain homeostasis.

2. 32.4 Excretory System

3. 32.4 Excretory System
The excretory system eliminates nonsolid wastes from
the body.
• Nonsolid wastes are
eliminated through lungs,
skin, and kidneys.
• Lungs exhale carbon
dioxide and water vapor.
• Sweat glands in skin
release excess water and
salts.
• Kidneys filter and clean the
blood to produce urine.
skin
lungs
kidneys
ureters
urinary bladder
urethra

4. 32.4 Excretory System
• Kidneys have three basic functions in maintaining
homeostasis.
– remove waste from blood
– help to maintain electrolyte, pH, and fluid balances
– release key hormones

5. 32.4 Excretory System
The kidneys help to maintain homeostasis by filtering the
blood.
• Kidneys are a pair of bean-
shaped organs.
– two layers: medulla and
cortex
– filtering units called
nephrons
– renal artery and renal
vein
cortex
medulla
renal
artery
renal vein
ureter
(to bladder)

6. 32.4 Excretory System
Nephrons clean the blood and produce urine.
• 4. Glomerulus-filters and cleans the blood
• 5. Bowman’s Capsule-holds the filtrate, molecules are
reabsorbed into the capillaries to balance the blood
chemically
• 6. Loop of Henle-
Water is reabsorbed.
7. Collecting ducts-
collect urine from
nephrons and
send it to the
ureter.
from body
to body
to body
from other
nephrons
loop of Henle

7. 32.4 Excretory System
Nephrons clean the blood and produce urine.
• Nephrons are the filtering units in the kidneys.
• They clean and rebalance the blood to produce urine.
from body
to body
to body
from other
nephrons
loop of Henle

8. 32.4 Excretory System
• Nephrons clean the blood in a three-step process.
• The first step is filtration of the blood.
FILTRATION
Water,electrolytes,aminoacids,
glucose,urea, and other small
molecules diffuse out of the
blood,creating the filtrate.
1
Glomerulus
Bowman’s capsule

9. 32.4 Excretory System
• The first step is filtration of the blood.
• The second step is reabsorption of materials.
• The third step is excretion of materials.
from body
to body
collecting
duct
from other
nephrons
loop of Henle
REABSORPTION
As the filtrate enters the rest of
the tubule ,most of the materials
are reabsorbed into the
blood.Materials not reabsorbed
make up the urine,which flows
into the loop of Henle.
2
EXCRETION
In the loop of Henle,water can be
reabsorbed one final time to
reduce the volume of urine.The
remaining urine flows into a
collecting duct that leads to the
ureter.
3

10. 32.4 Excretory System
Injury and disease can damage kidney functions.
• A kidney transplant can replaced damaged kidney.
– recipient and donor tissue must match
– drugs prevent tissue rejection
The daughter and son in this photo donated a kidney and
liver tissue to their mother.

11. 32.4 Excretory System
• Dialysis can be used to filter and clean the blood.

12. 32.4 Excretory System

13. 32.4 Excretory System
Hand-in worksheet on the
Excretory/Urinary System