The document summarizes the process of digestion in the human digestive system. It describes each organ involved and the roles they play, including the mouth, stomach, small intestine, large intestine, liver, gallbladder and pancreas. It details the mechanical and chemical breakdown of food, the enzymes and juices secreted by different organs, and how this leads to the absorption of nutrients and elimination of waste. The small intestine contains villi and microvilli that increase absorption surface area. The liver plays an important role in metabolizing nutrients and detoxifying substances.

1. Digestion

2. Label the following:
A:…………………
B: …………………
C:…………………
D:…………………
E:…………………
F:…………………
G:…………………
H:…………………
I:…………………
J:…………………
K:…………………
A
B
C
D
E
F
G
H
K J I
Mouth
Appendix
Stomach
Rectum
Large intestine/ colon
Small intestine
Pancreas
Anus
Liver
Oesophagus
Salivary gland

3. Each Tooth has a special shape
and role:
1. Incisors : sharp to cut and
bite food.
2. Canines: Sharp and pointed
to cut and tear.
3. Premolars: have cusps and
grooves to grind , crush &
chew the food.
4. Molars: same as premolars
but larger in size
Salivary glands produce Saliva ;
which contains:
1. Amylase enzyme
2. Mucin (slippery substance)
Canine
Incisors
Premolars
Molars

4. crown
root
Enamel
Dentine
Pulp cavity
Gum
Nerves
Blood vessels
Jaw bone
Cement

5. Tooth decay
Discuss what
brings about tooth
decay and what
could be done to
prevent it.

6. A:…………………
B: …………………
C:…………………
D:…………………
E:…………………
F:…………………
G:…………………
H:…………………
A B C
D
E
F
G
H
Label the following:
Duodenum
Pancreas
Pancreatic duct
Stomach
Oesophagus
Liver
Bile duct
Gall bladder

7. Stomach
Mechanical Digestion:
muscles of stomach keep
moving to churn up food just
like a blender.
Chemical digestion: The
gastric glands produce the
gastric juice that contains:
1. Pepsin enzyme
2. HCl acid
Other glands produce mucus
to protect the wall of the
stomach from the corrosive
acid.
Page 54 in BFU

8. Pancreas
Produces Pancreatic juice
that contains
1. Protease enzyme
2. Amylase enzyme
3. Lipase enzyme
4. Sodium hydrogen
carbonate
The pancreatic juice travels
through the pancreatic duct
to mix with food in the
duodenum.
Discuss the role of each of
the four constituents of the
pancreatic juice.

9. Liver and gall bladder
The liver produces the bile
juice which is stored in the
gall bladder and is released
through the bile duct to mix
with food in the duodenum.
The bile juice contains:
1. Bile salts
2. Bile pigments
3. Sodium hydrogen
carbonate
Bile salts help to emulsify fat;
change large drops of fat to
small droplets of fat.
How is emulsification useful?
Bile salts
Emulsification

10. Ileum
The ileum is lined
with many finger-
like projections
called villi which
help to increase the
surface area of the
ileum.
The increased
surface area helps
to increase the rate
of digestion and
absorption.
10

11. Villus
1. Each villus is covered with
a one cell thick layer called
the epithelium.
2. There is a network of
blood capillaries that help to
absorb glucose and amino
acids.
3. A blind-ended lacteal
absorbs the products of
digestion of fat.
4. It contains muscles to
move around; mixing food
with enzymes.
10

12. Features that increase the efficiency
of the ileum.
Think of the following questions to find how villi
are designed to maximize absorption.
• Why so many villi?
• Why a thin layer epithelium?
• Why do epithelial cells have microvilli?
• Why a dense network of capillaries?
• Why does the villus move?
10

13. Large intestine (colon)
Most of the food has been
digested and absorbed in
the small intestine.
In the large intestine some
salts and water are
absorbed.
The rest of the food
remains is mostly fibres
that cannot be digested ,
they will be stored in the
rectum and released
through the anus. This is
called egestion.

14. Liver and associated
blood vessels
The liver is the only
organ that has a blood
supply from an organ
other than the heart.
The Hepatic portal
vein carries blood rich
in glucose and amino
acids and other
molecules that must
be modified before
circulating around the
body.
Hepatic artery
(from heart)
Hepatic vein
(to heart)
Hepatic portal
vein (from ileum)
Liver

15. Roles of liver
1. It adjusts the blood glucose level.
2. Some of the glucose is used by liver cells in respiration. The pancreas
secretes insulin hormone when the blood glucose level rises above
normal. The hormone stimulates the liver to change the glucose into
glycogen to be stored in the liver cells.
3. Makes blood proteins e.g. fibrinogen using amino acids.
4. Performs deamination of excess amino acids to give two parts:
Nitrogen-containing part which become urea and is excreted by the
kidney. Remainder that can be respired to release energy.
5. Stores iron from worn-out red blood cells, which it breaks down,
excreting bile pigments.
6. Makes poisons harmless, this is called detoxification.
7. Makes bile salts which emulsify the fats in the intestine
8. Stores vitamins A & D.
9. The heat produced by the many metabolic reactions help to keep the
body warm.
10

16. Part of
alimentary
canal
Juices
secreted
from
Name of
juice
secreted
Juice
contents
What is
digested
Other points
Mouth
Stomach
Small
intestine
Large
intestine
Salivary
glands
Saliva •Amylase
•Mucin
Starch
maltose
Mucin makes
food slippery
Wall of
stomach
Gastric
juice
•HCl
•Pepsin
Protein 
amino acids
Starch 
maltose
Protein 
amino acids
Fats  fatty
acids +
glycerol
Liver
Pancreas
Bile juice
Pancreatic
juice
Bile salts
Alkaline sol
amylase
protease
Lipase
Alkaline sol
HCl kills
microbes
Bile salts
emulsify fats
Absorption of
water &
digested food
molecules
None None None None
Absorption
of water and
minerals