Transcript Digestive Tract

Digestive enzymes
Starch
AMYLASE
Proteins
PROTEASE
Lipids/ Fats
LIPASE
maltose
amino acids
fatty acids &
glycerol
 identify and describe the main
regions of alimentary canal
 describe the functions of the parts of
the human gut and the associated
organs
Pathway of Digestion in Alimentary Canal
Mouth
↓
Oesophagus
↓
Stomach
↓
Small Intestines
↓
Large Intestines
↓
Rectum
↓
Anus
• Digestion is the process of breaking down
complex, large molecules (food) into simple,
soluble and diffusible molecules so that it can
be absorbed by the body and be used to build
and nourish cells and to provide energy.
Functions of digestive system:
(1) Ingestion: taking food into the body.
(2) Digestion: breakdown of food materials
into smaller amounts
(i) Mechanical digestion
(ii) Chemical digestion
(3) Absorption
(4) Assimilation
(5) Egestion
Types of digestion:
(i) Mechanical digestion
• Break down particles into smaller pieces so as
to increase the surface area for the action of
enzymes.
(ii) Chemical digestion
• Involves enzymatic reactions which digest the
food into simpler chemical forms.
• Hydrolysis splits the large molecules by addition
of water.
How is Food Digested?
Mouth
• Ingestion is the process of taking food
into the body.
• The tongue rolls and lubricates food with
mucus and saliva.
• Chemical digestion of starch starts here
by salivary amylase.
Oesophagus
• It takes food down from the throat and
into the stomach. Moving food by waves
of muscle contraction called peristalsis.
The oesophagus
Circular muscles
contract to push
the food ball
down.
The partially digested
food is pushed to the
stomach by wave-like
contractions known as
peristalsis.
Circular
muscles relax,
and the tube
widens for food
to move.
The stomach
Stomach
• The stomach lining produces mucus and gastric juices
which contains:
i) hydrochloric acid (acidic medium of pH 2 for
enzymes and kills micro-organisms in food)
ii) Pepsin: hydrolyze protein to polypeptides.
iii) Rennin: hydrolyze milk caseinogen to casein.
stomach
Quick Revision:
What is the function of hydrochloric acid?
1) Provides an acidic medium for
activation of gastric enzymes.
Inactive forms
Active forms
Prorennin HCl
Rennin
Pepsinogen HCl
Pepsin
2) Kills germs and potential parasites.
3) Stop the action of salivary amylase.
You should:
• take multiple small
meal at regular intervals,
• take less protein per
meal
• clean and cook the food
thoroughly……
Dr. Jones, I am suffering
from stomach cancer &
half of my stomach was
removed.
What should I do?
Oh dear….i feel that my
chest is burning after
having a heavy dinner.
What could have gone
wrong?
Inflamed
oesophagus
This condition is due to
the irritation of the
oesophagus that is caused
by
too much stomach acid.
The Liver & Gall Bladder
 A small pear-shaped
organ that is greenishyellow in colour.
 Temporarily stores bile
secreted by liver.
QUESTION:
Will bile secretion be
hindered if the gall bladder is
removed?
THE STRUCTURE & FUNCTIONS OF …

Liver and Gall Bladder

Pancreas

Small intestines

Large Intestines

Rectum and Anus
LIVER:
 Largest gland in the
body.
 Lies below
diaphragm, on right
side of body.
 Secretes bile.
QUESTION: Can bile digest food?
Bile is not an enzyme, so it cannot
digest food but it aids in digestion of
lipids.
Emulsification
Bile
Large oil drop
Small oil droplets
The Pancreas
Connected to
duodenum by
pancreatic duct
 Secretes pancreatic
juice that contains
digestive enzymes.
Small Intestines
(Duodenum, jejunum and ileum)
• Major site of chemical digestion
of all remaining food
(carbohydrates, fats and
proteins).
• Also, main site of absorption of
nutrients occur here.
The Large Intestine
 Contains undigested
food material.
 Main function is to
absorb water and mineral
salts.
 Rectum temporarily
stores faeces that are
egested through the anus.