1. removal of metabolic waste
Excretory System:
removal of metabolic waste

2. Principal Wastes of Excretion
Metabolic Activity
Wastes Produced
Respiration
Carbon dioxide and water
Dehydration Synthesis
Water
Protein Metabolism
(deamination)
Nitrogenous wastes
(Ammonia, urea, uric acids)
Other metabolic activities
Mineral salts
These wastes are often toxic to the organism and must be removed
Excretion: removal of the wastes products of metabolism

3. What liquid waste do we make?
Digesting protein makes poison
nitrogen waste = ammonia = poison H |
—C—
C—OH || O H N
CO2 + H2O H
NH2 + H+ = ammonia NH3

4. Nitrogen waste The kind of waste you make depends on where you live
Freshwater
Ammonia directly into environment
Land
Urea
Urine
Land egg layer
uric acid
Non-toxic; crystalline
Mode of reproduction appears to have been important in choosing between these alternatives.
Soluble wastes can diffuse out of a shell-less amphibian egg (ammonia) or be carried away by the mother’s blood in a mammalian embryo (urea).
However, the shelled eggs of birds and reptiles are not permeable to liquids, which means that soluble nitrogenous wastes trapped within the egg could accumulate to dangerous levels (even urea is toxic at very high concentrations).
In these animals, uric acid precipitates out of solution and can be stored within the egg as a harmless solid left behind when the animal hatches.

5. Excretion in Plants
Because the wastes of photosynthesis are the reactants of respiration, plants have few wastes to excrete
Excess CO2 and H2O can be released through stomates
Some wastes can be stores in plant cell vaculoues

6. Excretion in Simple Organisms
Protozoans and Hydra: wastes are released through the cell membrane directly into the watery environment
In paramecia, excess water is pumped out by a contractile vacuole

7. Excretion in Simple Organisms
Earthworm: Carbon dioxide is excreted through moist skin
Nephridia: excretory tissue that absorb water, excess salts, urea and ammonia

8. Excretion in Simple Organisms
Grasshopper: Malpighian tubules open into the digestive tract, removing wastes from the blood
Nitrogenous wastes are converted to uric acid
CO2 is released through tracheal tubes and then spiracles

9. Human Excretory Organs
Lungs: CO2 and diffuses from the blood into the alveolar space and is then exhaled, along with some water vapor
Liver: large glandular organ that performs many functions, including excretion
Disposal of Hemoglobin: old red blood cells are broken down in the liver, creating bile salts which are eliminated in feces
Disposal of nitrogenous wastes: amino acids are broken down in the liver forming urea, which is filtered out of the body by the kidneys

10. Human Excretory Organs
Sweat Glands: small, coiled tubular exocrine glands found in the surface of the skin
Sweat contains water, salts and some nitrogenous wastes
Perspiration: formation of sweat
Sweat is very important for temperature regulation
Evaporation of sweat helps to cool the body

11. Human kidney Mammals have a pair of bean-shaped kidneys
supplied with blood by a renal artery and a renal vein
Functional unit is a nephron
In humans, the kidneys account for less than 1% of body weight, but they receive about 20% of resting cardiac output

12. 1. blood flows through capillaries into glomerulus
2. Filtration: water, salts, urea, amino acids, glucose diffuse out of blood into Bowman’s Capsule
3. Reabsorption: some water, salts, amino acids, glucose are reabsorbed through active transport into capillaries
1. blood flows through capillaries into glomerulus
Proximal
tubule
Distal tubule
Glomerulus
Collecting
duct
Loop of Henle
Amino
acids
Glucose
H2O
Na+ Cl-
Mg++ Ca++
Bowman’s capsule
4. Excretion: fluid formed at end of tubule consists of water, salts, urea, called urine

13. Endocrine System Control
increase thirst
ADH
pituitary
increased water reabsorption
nephron
high
blood osmolarity
too many solutes in blood
dehydration, high salt diet
release ADH from pituitary gland
antidiuretic hormone
increases permeability of collecting duct & reabsorption of water in kidneys
increase water absorption back into blood
decrease urination

14. Human Excretory Organs
Bladder
Urinary Bladder: urine is brought to the bladder for temporary storage by two ureters.
The bladder eliminates urine through the urethra.

15. Malfunctions of the Excretory System
Kidney Disease: many diseases affect the kidney
This could be caused by a diet high in protein exceeding the capacity of the kidney
Gout: a form of arthritis in which excess uric acid crystallizes in the joints