Transcript 2.3 HUMAN DIGESTIVE SYSTEM

2.3 HUMAN DIGESTIVE
SYSTEM
Learning outcome
• explain what digestion is.
• identify the parts of the digestive system.
• describe the flow of food particles in the
alimentary canal.
• state the functions of the organs in the
digestive system.
• describe the process of digestion in the
alimentary canal.
• list the end products of digestion of
carbohydrate, protein and fats.
Digestion
• Process of breaking down complex food to
simple molecule for absorption into the
blood circulatory system.
• 2 stages:
– Physical digestion – big pieces of food are
broken down into smaller pieces by teeth
– Chemical digestion – enzymes break up
complex food molecules into smaller
molecules.
Enzyme
• What is enzyme????
– Protein that speed up the process of digestion.
• Characteristic of enzymes
–
–
–
–
required in small quantities
Not destroyed at the end of digestion
Act only specific foods
Function best at normal body temperature (37
celcius). It destroyed at high temperature.
– Specific enzyme act only in specific acidic or alkaline
conditions.
Digestive system
• What must you know????
• Organ that involve in digestive system..
– Mouth, oesophagus, stomach, pancreas, bile duct, gall
bladder, liver, small intestine, large intestine, large
intestine, anus
• Alimentary canal start from mouth, oesophagus,
stomach, small intestine, large intestine and the end
at anus.
• Process of peristalsis – food that pushed along the
alimentary canal by contract and relax of muscular
walls
Mouth (physical digestion)
• Food chewed and broken up into small pieces by the teeth.
• Small pieces of food have wide surface are for the saliva to
act upon.
• The salivary gland secrets saliva that is alkaline and contains
salivary amylase
• Salivary amylase convert starch into maltose
Salivary amylase
Starch
maltose
Oesophagus
• No digestion take place. Why???
• Food from mouth pushed through oesophagus(gullet)
into the stomach by the alternating muscular contraction
and relaxation of the oesophagus
• Process peristalsis.
Stomach
• Food mixed with gastric juice
• What is gastric juice???
– Juice that secreted from the cell at stomach wall.
– Contain Hydrochloric acid and enzyme rennin and
pepsin
Hydrochloric acid
• Function of hydrochloric acid
– Providing and acidic medium for enzymic action
– Killing bacteria found in food
– Neutralising the alkaline property of saliva and
stopping the action of salivary amylase
Cont…
• Pepsin
– Digest protein into peptones
Protein
Pepsin
Peptone
• Rennin
– Coagulates milk in the stomach to help in the
enzymic action of pepsin
Liquid milk protein
Rennin
Solid milk protein
Small intestine
• The duodenum is first part of the small
intestine
– Receive bile and pancreatic juices
Bile
• Bile produced by liver and stored in the gall
bladder.
• Bile flows from gall bladder into the
duodenum through the bile duct.
• Function of bile:
– Emulsification of fat
– Preparation of an alkaline medium for enzymic action
Pancreatic juice
• Produced by pancreas cell
• Contain 3 type of enzyme
– Pancreatic amylase(digest starch)
Pancreatic amylase
• Starch
maltose
– Protease( digest peptones)
• Peptones Protease
amino acods
– Lipase
lipase
• Fat
fatty acids+ glycerol
• Small intestine also produce enzyme maltase
that digest maltose into glucose
• Digestion is completed in the small intestine
• It ready to be absorbed into the blood stream
through the thin wall of the small intestine
Large intestine
• Absorb water
• Undigested food is expelled from the body
through the anus as faeces
End products of digestion
• The end product must in simple forms that
readily absorbed into the small intestine
through villi
Class of food
Final product of digestion
Carbohydrate Glucose
Starch
Protein
maltose
maltase
glucose
Amino acid
Protein
Fat
amylase
pepsin
peptones
protease
amino acid
Fatty acid and glycerol
Large fatty globules
bile
small droplet
lipase
fatty acid
and glycerol
The end