Lesson two
the human respiratory system
The respiration Process
 A process which provides the body with energy.
 The importance of respiration process:
1) Producing needed energy for vital activities (motion and sensation).
2) Taking oxygen gas and get rid of harmful products (Carbon dioxide and
water vapour).
 The most organs of the respiratory system exist in thoracic (chest) cavity.
The structure of respiratory system
 The respiratory system consists of: A) Nose : Has
 Mucous layer and hair: Filter the air from dust and microbes before
entering the lungs.
 Blood capillaries: - Warm the air.
Give reason:
Breathing through nose is preferable to that through mouth.
…………………………………………………………………………………..
7
Pharynx
A common cavity leads to the esophagus and trachea.
Allows air to pass from the nose to the larynx.





Larynx (voice box)
At the top of trachea.
It contains the two vocal cords (vibrate to produce sound).
Epiglottis
Lies at the top of larynx.
It closes the trachea during swallowing.
It prevents food from entering the trachea.
Trachea
Trachea is a tube supported with:
Incomplete cartilaginous rings that make it open all the time.
Lined with cilia to eject up the strange objects as dust.
The bottom of trachea branches into two
narrow tubes called bronchi
Lungs
They occupy the thoracic cavity.
They are surrounded by ribs (rib cage).
Each lung contains bronchus which is
divided into bronchioles
Bronchioles end in tiny air sacs
called Alveoli.
The air sacs are surrounded by networks of
blood vessels.
The importance of two lungs:
They have air sacs to make gases exchange.
Diaphragm:
 It is a muscle that separates the thoracic (chest) cavity from the abdominal
cavity.
 It has an important role in the respiration process.
8
 Give reasons:The alveoli surrounded by a network of blood capillaries.
To allow gases exchange between the air sacs and the blood.
The respiration:
 Decreases during sitting, increases during
walking and more increasing during running.
Give reasons:
 The respiration times increase during running.
 Because, running needs more energy which needs
more oxygen gas to burn more food.
Mechanism of respiration
During inhalation
During exhalation
1- The diaphragm muscle contracts
and moves down.
1- The diaphragm muscle relaxes and
moves up.
2- The ribs rise upwards.
2- The ribs move down.
3- Chest volume increase
3- Chest volume decreases.
4- Air rich with oxygen enters lung. 4- Air rich with carbon dioxide and water
vapour moves outside the lungs.
9
To test for carbon dioxide gas:
- The carbon dioxide gas turbid the clear lime water.
Exchange of gases
 Exchange of gases occurs between air exists in
alveoli and the blood in the blood
capillaries.
 Carbon dioxide gas transfers from blood to air sac.
 Oxygen gas transfers from air sac to blood.
 How to keep the respiratory system healthy?
 Avoid crowded or poor aerated places.
 Avoid smoking – smokers because it causes damage in respiratory
system.
 Keeping off the severe cold.
 Breathe by nose not by mouth.
 Eat fruits rich in vitamin (C) such as oranges, guava to protect us
from diseases.
Respiration: is the process carried out by human in order to get energy from
burning of the digested food.
The more active your body is, the more your respiration times increases
Exhalation air contains carbon dioxide and water vapour as products of
respiration process.