The document summarizes the excretory system and its key organs. The lungs, skin, colon, and kidneys work to remove waste from the body. The lungs exhale carbon dioxide, the skin sweats out water and salts, the colon removes bacteria and waste from digestion, and the kidneys filter waste from the bloodstream and regulate water and salt levels. The liver also plays an important role in breaking down toxins, drugs, and other substances before they are excreted by other organs.

1. THE NUTRITION FUNCTION II
The excretory system.

2.  Certain waste products would become highly
toxic if they were to accumulate. This could
damage tissues.
 An excess of water could also lead to a number
of complications.
 Thus, the waste products must be removed –
they continually move into the bloodstream,
which carries them to the excretory organs.

3. Raw Materials
(Food and 02)
Useful Materials
Useless Materials
Egested (faeces) Metabolised
Metabolic Waste
Products (urea and
CO2)
Excreted
Useful Products

4.  There are four main excretory organs:
 Lungs
 Colon (large intestine)
 Skin
 Kidneys
 The liver is not an excretory organ, but produces many
products which are excreted elsewhere. Toxins and
drugs as well as alcohol, is broken down in the liver.
Hence, an excess of smoking, medication and alcohol is
extremely harmful to the liver.

5.  The carbon
dioxide released
from cellular
respiration is carried
to the lungs in the
blood. It then diffuses
across the respiratory
membrane and is
exhaled.
 A small amount of
heat and water is

6.  Bile pigments, from the break
down of haemoglobin, and
cholesterol are synthesised
in the liver.
 They pass into the small
intestine as bile and are finally
excreted in the faeces as bile
salts, from the colon.
 Mucus and bacteria are too
excreted through the colon.

7.  Sweat, which is excreted through the skin, contains water,
salts and some urea.
 As the water in the sweat is excreted, heat is lost and the
body is cooled.
 Sweat is a form of excretion as it rids the body of waste, as
well as a form of secretion as it maintains the body
temperature.

11.  The main function of the urinary system is to maintain
homeostasis by regulating the volume and concentration of
body fluids. It filters and reabsorbs certain materials from the
blood.
 The urinary system is made up of
the following parts:
A) Two kidneys
B) Two ureters
C) A bladder
D) An urethra

12.  The kidneys aid in:
 excretion as they filter
waste out of the blood
 regulate the water and
salt balance in the body.
 They secrete some
hormones, that control
blood pressure or red
blood cell production, for
example.
One kidney – the right
kidney – is slightly lower
than the left as it is pushed
down by the liver, which is

13.  Renal artery: carries
waste products to the
kidney and supplies
the kidneys with
oxygen and nutrients.
 Renal vein: contains
the purest blood in the
body. It carries CO2
to the inferior vena
cava.

14. Glomérulo
Arteriola

15.  Stores urine.
 Is stimulated by impulses from a motor nerve, to contract to expel the
urine (micturition reflex).
 Has sphincter muscles at the base to control the flow of urine.
 Carries urine from the bladder to outside the body.
 A MAN’S urethra is CONNECTED WITH A DUCT OF THE
REPRODUCTIVE SYSTEM.
 A WOMAN’S urethras are INDEPENDENT OF HER REPRODUCTIVE
SYSTEM.
 Carry urine from the kidneys to the bladder.

17. 1º. Glomerular filtration:
Water, salts, nutrient and
waste molecules move
from the glomerulus to
the inside of the
glomerular capsule.
2º. Tubular reabsortion:
Nutrient and salt
molecule are reabsorbed
from the convoluted
tubules into capilaries.
3º. Tubular secretion:
Certain molecules are
secreted from capilaries
into convoluted tubules