CHAPTER1: RESPIRATION

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1.1 Human Breathing Mechanism



1. Living things get their oxygen supply from the around them.
2. We breathe in oxygen for respiration and breathe out carbon dioxide and water vapour is produced during respiration.
3. "Breathing" is physicall which involves exchanges of oxygen and carbon dioxide in our body.

1.1.1 Human Respiratory System

The stucture of the human respiration system :

•  Breathing consists of two stages:

         a.Inhalation - during which air is taken into the lungs.

         b.Exhalation - during which air passes out of the lungs.

• The breathing system or the human respiratory system consist of the following structures or organs :

         a. The nasal cavity              c. Bronchus (plural: bronchi)

         b. Trachea                           d. Bronchiole                                                               

                                                                              

          

        e. Lungs   

        i. Alveolus (plural: alveoli)                                 

        f. Rib cage

        g. Diaphragm

        h. The intercostal muscles

        i. Internal intercostal muscles,

        ii. External intercostal muscles

6. Flow of air into the lungs

 a. Air is breathed in through the nose and enters

     the nostrils.

b. The nostril leads to the nasal cavity where the air

     is warmed up and moistened.

b. The nostril leads to the nasal cavity where the air

i. Hairs and sticky mucus trap particles inside the nasal cavity.

c. The air then enters the trachea.

 

d. The trachea branches into two bronchi.
i. Each bronchus leads directly into a lung.
ii. The bronchus branches into many smaller

tubes called bronchioles

e. The air then passes through the bronchiole and comes to alveolii. The human lungs have millions of alveoliii. The wall of the alveolus is only one-cell thick.
iii. It is thin , moist and is surrounded by a network of capillaries.

iv. The exchange of respiratory gases, oxygen and carbon dioxide, occurs between occurs between the alveolus and capillaries.

1.   The breathing mechanism is the  physical changeswhich occur in the respiratory system during breathing 

           2.   This mechanism involves

                 a.inhalation (breathing in),

                 b.exhalation (breathing out).

          

            3.    During inhalation

           a. Both the intercostal muscles and the diaphragm contract

           b. The diaphragm moves downwards,increasing the volume of the thoracic (chest)

                cavity



           c. The intercostal muscles pull the ribs up ,expanding the rib cage
               and further increasing the volume of the thoracic cavity.

           d. These actions lower the air pressure in the alveoli

           e. Air from the outside then rushes in through the nasal cavities,
              trachea and lungs. The lungs expand.

 

                a. The intercostal muscles relax causing the

                    rib cage to move downwards  and inwards

                b. The muscles of the diaphragm relax and

                    the diaphragm curves upwards curves upwards and

                    returns to its original dome shape

               c. These actions return the thoracic cavity to its original volume

               d. The air pressure inside the lungs is now

                    higher than the atmospheric pressure outside.

               e. The lungs contract and the air is forced out through the respiratory tract.

Composition of inhaled air and exhaled air:

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