Lesson one
Human digestive system
All living organism's have common characteristic such as nutrition,
transport, respiration, excretion, motion, sensation, reproduction.
The structure of the living organism body:The human body consists of a set of system.
Human Body Systems
The System
1
 The digestive system
Its Function
 Digests and absorbs food.
2
 The respiratory system
 For breathing.
3
 The circulatory system
 Distributes the digested food and
oxygen all over the body cells.
4
 The urinary system
 Gets rid of harmful substances.
5
 The nervous system
 Responsible for sensation process.
6
 The reproductive system
 To give birth for new individuals
who will look like us.
All systems are working in full harmony and integrity together
To keep the human life goes on.
Urinary system
Digestive system
1
The human Digestive System
The digestion Process: Changing the food from a complex form into a simple one to let the body
get benefit from it.
 Break down of food to get benefit from it.
Give reason:
 Digestion process is very important to the human body.
Because it converts the complex food into simple substances to let the body
benefit from it.
The digestive System Structure:
Digestive system
Digestive canal
Mouth - pharynx- esophagus – stomach
– small intestine – large intestine –
rectum - anus
Digestive canal Supplementaries
Salivary gland- Liver - Pancreas
The digestive canal
 A set of organs which connected to each other in shape of a long pipe(duct)
 It has (9-10) m. length.
 It starts with the mouth and ends in the anus.
The digestive canal supplementaries
 There are three types of glands
are connected with this canal:
A- The salivary glands.
B- The liver.
C- The pancreas.
2
The digestive canal
A) Mouth
 Teeth:- it has
 The teeth number in an adult are 32.
 Each jaw has 16 teeth, divided into
(4 incisors, 2 canines and 10 molars).
 Incisors and canines cut and tear food into small pieces.
 Molars grind the food to make swallowing easy.
 Tongue: It turns food inside the mouth cavity.
 Mixes food with saliva to help in swallowing and tasting the food.
 Salivary glands: They are three pairs of glands secrete saliva.
 The saliva contains digestive substances called enzymes.
 The enzymes digest starch to sugar.
Give reasons:-
(1) After chewing a piece of bread in the mouth, we feel a sweetly taste.
(2) Digestion of food starts at the mouth.
Because, the mouth contains saliva which digests starch into simple sugar.
(3)Food should be chewed well in the mouth.
To be easy to swallow, and change starch into simple sugar by saliva
B) Pharynx:
 It is a common cavity between digestive and respiratory system and leads to
the esophagus and trachea.
 It passes food from the mouth to the esophagus.
3
 C) Esophagus
 It's a muscular tube connecting to the stomach.
 It allows food to pass from the pharynx
to the stomach.
 D) Stomach : - A muscular sac.
 Help in mixing food by its juices.
 It secrets gastric juice.
 An incomplete digestion of protein
takes place by a gastric juice.
 E) Small intestine
 Its length is about seven meters.
Stomach
 It starts with duodenum followed by ileum.
Small intestine
 It has a bile juice :
o secreted by liver
o Breaks down fats and oil into small
particles that dissolve in water
forming emulsion.
Duodenum
 It has pancreatic juice:
o Produced by pancreas.
 The complete food digestion takes
place in it by using intestinal juice.
ileum
 Absorption process takes place in it
by villi.
4
Absorption process
 Passing the digested food from small intestine to blood.
 In the digestive system, food undergoes two processes which are digestion
and absorption.
F) Large Intestine
 Starts from the end of small intestine
and ends by anus.
 It stores wastes then ejects them outside the body
through anus.
 The function of rectum: It absorbs the water
from the food remains.
Large
Intestin
Rectum
Anus
How to keep the digestive system healthy?
 Chew the food well.
 Don't eat much food that contains large amounts of fats such as fast meals.
 Avoid food with additives.
 Don't buy food from street sellers.
 Practice sports regularly.