Excretion
Excretion
Removal of metabolic wastes
Metabolism:
Chemical reactions that build up, break
down or change compounds
Macromolecule Metabolism
used
Cellular
Respiration
Carbohydrates
C
H
O
Stored
Glycogen
Lipids
product
ATP
waste
CO2, H2O
Macromolecule Metabolism
Stored
Lipids
C
H
Fat
O
As lipids (hormones,
cell parts, etc. )
Used
Converted back to
carbohydrates
waste
“Ketones”
Macromolecule Metabolism
Used
Protein
C
H
O
Enzymes,
Hormones,
Chaperones,
Cell parts, etc…
N
Converted to
In the liver
Muscle waste
(ATP use)
Lipids,
Carbohydrates.
(C – H – O)
Heat,
Other
wastes
What happened to
the Nitrogen?
Nitrogenous Waste
• Nitrogen from protein “deamination” is in
the form of ammonia
NH3
(Very Toxic)
Ammonia Excretion
Ammonia
Uric acid
Urea
The Liver
• Major Vital organ
• Processes most macromolecules and ingested
toxins (including medicines and alcohol)
• Blood and lymph vessels carry materials absorbed
in the small intestines directly to the liver for
processing
• Doesn’t remove any wastes, just processes things
so they may be removed.
Excretory organs
Skin  sweat H2O, urea, salts
Lungs  breath CO2, H2O
Liver doesn’t remove wastes detoxifies and
deaminates
Urinary system = kidneys, ureter, bladder,
urethra make urineH2O, urea, salts and
surplus stuff (vitamins, sugars, etc.)
Note = this does not include the digestive system 
Feces are not really excretory (its not a metabolic
waste)
The Urinary System
ADRENAL GLAND – not excretory
KIDNEY
URETER
URINARY BLADDER
URETHRA
The Kidney
The Kidney Bean
URETER
The microscopic, functional unit of the
The Nephron kidney.
There are millions of these in
each kidney
How to make URINE:
1. Filtration: All dissolved
material leaves blood.
This occurs here
2. Reabsorption: “good”
material returns to the blood
This occurs here
What is left over is…URINE!