2.3 human digestive system
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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 Peptone
• Rennin– Coagulates milk in the stomach to help in the
enzymic action of pepsin
Liquid milk protein Solid milk proteinRennin
Pepsin
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)• Starch maltose
– Protease( digest peptones)• Peptones amino acods
– Lipase• Fat fatty acids+ glycerol
Pancreatic amylase
Protease
lipase
• 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 maltose glucose
Protein Amino acid
Protein peptones amino acid
Fat Fatty acid and glycerol
Large fatty globules small droplet fatty acid and glycerol
amylase maltase
pepsin protease
bile lipase
The end