Digestion is the process by which food is broken down into smaller molecules that can be absorbed by the body. It involves both mechanical and chemical breakdown of food. In the mouth, teeth chew food and saliva contains the enzyme amylase. The esophagus transports food to the stomach through peristalsis. The stomach contains acid and enzymes that break food down further. The pancreas and liver secrete enzymes and bile that aid in digestion within the small intestine. Nutrients are then absorbed through the intestinal walls and remaining waste is eliminated from the anus.

1. Digestion
Done by: Ooi huiying

2. Digestion
 The process whereby large food
molecules are broken down into smaller,
soluble, diffusible, simpler forms that can
be absorbed into our body.
 Physical-Mechanical breakdown of food
into smaller particle
 Chemical- Enzymatic hydrolysis of food
substances

3. Mouth & Buccal Cavity
Mouth
The opening that food enters & leads to the
buccal cavity.
Buccal Cavity
Tongue- Mixes food with saliva (Amylase)
- Rolls food into Bolus
- Pushes food down the Pharynx
Teeth- Chews food into smaller pieces for
enzymatic reactions. (mastication)

4. Oesophagus ( gullet)
 Consist of the inner circular muscles and outer
longitudinal muscles.
 Does not digest food.
 It is a muscular tube that pushes food down
the body through peristalsis.
 Peristalsis is the strong and rhythmic
movement.
 The inner circular muscles relaxes and the outer longitudinal muscles contracts, the
lumen widens for food to enter.
 When the inner circular muscles contracts and the outer longitudinal muscles relaxes,
the food is pushed forward.

5. Stomach
 A distensible, muscular bag with thick and well-
developed muscular walls.
 It creates powerful muscular contractions called
churning, which mixes food with gastric juices to
form chyme.
 Gastric juice : Hydrochloric acid
Protease(Digest proteins)
 Acidic environment: To kill germs & pasticides.
Provide an optimum environment for protein
digestion (Ph 1-2.5). Stop action of salivary
amylase

6. Small intestine
 6m long connected with liver and pancreas.
 Consists of : U-shaped duodenum
Jejunum
ileum
 Bile
 Pancreatic juice : Pancreatic amylase,
Pancreatic lipase, protease
 Intestinal juice: Peptidase,maltase,lipase
 Mucus is produced.

7. Villus
 Finger-like
structures which increases
surface area for digestion

8. Liver
 Produces a yellowish-green fluid called
bile.
 Bile does not contain enzymes but helps in
fat digestions through the process of
emulsification.
 Emulsification is the breaking down of fats
molecules into smaller droplets to increase
surface area for fat digestion.
 Bile is temporarily stored in gall bladder.

9. Pancreas
 Situated between stomach and small
intestine.
 Secretes pancreatic juice (alkaline)
containing amylase, protease.
 Alkaline juice neutralizes the acid in the
food from stomach.

10. Large intestine
 About 1.5 m long
 Absorbs remaining water and minerals
salts.

11. Rectum
 Near
solid waste called Faeces is
temporarily stored in the rectum.

12. Anus
 Faeces is forced out of the gut through
anus. (Egestion)
 Faeces contains mainly digested food
and unabsorbed material.
 Faeces contains dead bacterial,
cellulose, mucus, cholestrol,water.

13. Enzymes & their reactants
Enzymes reaction
Protease Proteins- Amino acids
Lipase Fats- glycerol + fatty acids
Amylase Starch- maltose
Maltase Maltose- glucose

14. Enzymes.
 Pancreatic juice : Amylase, maltose
protease, lipase.
 Intestinal juice : Maltose, protease, lipase