1. The Digestive System Biology Grade -9-
Prepared by teacher: Ronak Ahmed
International School/ Duhok

2. Why you fell hungry
Because your brain receives signals that your cells need energy!!
But eating is only the beginning of the story. Your body must change a meal into substances that you can use.
What is digestive system?
It’s a group of organs that work together to digest food so that it can be used by the body.

3. Digestive system at a Glance
The most obvious part of your digestive system is a series of tubelike organs called the digestive tract.
Food passes through the digestive tract
Including:
9 m
Mouth.
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
Is their other organs in digestive system?
Yes, the liver, gallbladder, pancreas, and salivary glands are also part of the digestive system.
But the food does not pass through these organs.

4. Breaking down food Mechanical Chemical
What will happen to food such as falafel, kabab, candies, chocolate and dessert in digestive process?
The food will break down into a form that can pass from the digestive tract into the bloodstream.
Types of digestion
Mechanical
The breaking, crushing, and mashing of food.
Chemical
Large molecules are broken down into nutrients.
The importance of nutrients:
Are substances in food that the body needs for normal growth, maintenance, and repair.

5. Types of nutrients in your food
Carbohydrates
Proteins
Fats
What is enzymes?
Substances break some nutrients into smaller particles that the body can use.
Why enzymes cut protein into smaller pieces?
Because proteins are too large to be absorbed into the bloodstream

6. The role of enzymes in protein digestion
Enzymes act as chemical scissors to cut the long chains of amino acids into small chains.
The small chains are split by other enzymes.
Individual amino acids are small enough to enter the bloodstream, where they can be used to make new proteins.
Self-Check
How do enzymes help digestion?
Enzymes cut proteins into amino acids that the body can use.

7. Digestion begins in the mouth
Video
Why chewing is important?
1- Chewing creates small, slippery pieces of food that are easier to swallow than big dry pieces are.
2- Small pieces of food are easier to digest.

8. Teeth Teeth are very important organs for …………………….
Mechanical digestion
Teeth are very important organs for …………………….
What helping teeth break and grind food?
Chemical digestion
Strong jaw muscles
what is the hardest material in the body?
Enamel, which is the outer most layer of a tooth.
What is the function of enamel?
Enamel protects nerves and softer material inside the tooth