Science Grade 4 First term Concept 1 1 Lesson 3

Lesson 3Digestive system
To get nutrient from food, food must be digested
Digestive system: • system which breaks down food into small pieces
Digestive system starts with mouth and ends with anus
1. Mouth: Digestion process starts in mouth
• Mouth contains:
1-Teeth: chewing food
2-Saliva: A liquid moistens food to facilitate swallowing food.
3-Tongue: it mixes food with saliva
Esophagus:
It moves food down into stomach
Stomach:
It mixes food with stomach acid and digestive juices to change food into soupy juice.
Small intestine :
-It’s a 6-meter-long winding tube
-Liver and pancreas secrete juice in small intestine to break food into nutrients.
-It makes complete digestion and absorbs nutrients.
Large intestine
• It absorbs water from undigested food to produce solid waste, so they become solid wastes that leave the body through the anus.
How can you keep your digestive system healthy?
1-Chew the food well
2-don’t eat much fast food
Notes:-
System; It is a group of organs that work together
Digestive system and respiratory system are working together to get energy from food and breathing. 
Respiratory system
Respiratory system : • System responsible for breathing (respiration)
Respiration process: • A Process by which oxygen gas gets into lungs and get rid of carbon dioxide out of the body
Respiratory system consists of: (Nose - Throat - Trachea - 2lungs - Diaphragm)
Function of respiratory system organs
Nose: The first organ in respiratory system
Throat: Allow air to pass from nose to trachea
Trachea: Allow air to pass to lungs
Lungs: it has alveoli which makes gas exchange
Diaphragm: A muscle helps in inhalation and exhalation .
How the respiratory systems does works
1. During inhalation, the air enters through the nose and the
mouth, then to the throat until it reaches the two
lungs
2. trachea is branched into two bronchi that are divided into smaller tubes called bronchioles.
3. Air sacs(alveoli) extract oxygen from the air.
4. Blood carries oxygen gas to all body parts to do their functions
(1) Inhalation
1. Diaphragm contracts and moves down
2. Oxygen gas enters two lungs.
3. Chest size increases.
(2) Exhalation
1. Diaphragms relaxes and moves up.
2. Carbon dioxide is expelled outside the body.
3. Chest size decreases.
Diaphragm: A large muscle that directs Inhalation and exhalation processes.
How can you keep your respiratory system healthy?
1. Avoid smoking
2. Breathe in clear air
3. Eat healthy food rich in vitamin c
Complete the following:
1. The human body uses digestive system to get nutrients from food and uses respiratory system to get oxygen from air
2. In order for food to become soft tongue and teeth work to mix and grind the food well.
3. In the digestive system, food becomes a soupy liquid in the stomach while breaks down into nutrients in small intestine
4 The esophagus is a tube that has muscles to move the food down into the stomach, while small intestine is a long winding tube, its length is more than six meters.
5. The longest part of the digestive system where most digestion takes place inside it is small intestine
6. The respiratory system supplies the body with oxygen gas and gets rid of carbon dioxide gas
7. Inside the lung, the trachea is branched into two bronchi that are divided into smaller tubes called bronchioles
8. The alveoli plays an important role in extracting oxygen gas from the air.
9. The blood plays an important role in carrying oxygen gas to all body parts.
❹Give reason:
1. The importance of juices of liver and pancreas.
Because it help in digestion process and break down food into nutrients.
2. Anus is an important organ in the digestive system.
Because it help to get rid of waste material out of the body.
3. The inhaled air differs from the exhaled air.
Because inhaled air contain oxygen gas while exhaled air contain carbon dioxide gas.
❺What happens if...?
1. The small intestine is removed from the human body.
We cannot complete digestion process or absorbs the needed nutrients.
2. The nutrients absorbed by the walls of small intestine enter the tiny blood vessels.
Blood vessels carry nutrients to all body.
3. The diaphragm moves downward during inhalation.
The oxygen gas enter the two lungs and chest size increase.
4. The diaphragm moves upward during exhalation.
Carbon dioxide is expelled out of the body and chest size decreases.