-The nose is the passage of air into the lungs. As the air moves through the passage, its warmed and moistened.

-The trachea is a tube made up of rings of cartilage which ensures it does not collapse during breathing. Its lumen is lined with ciliated epithelium. The cilia wafts the mucus and foreign particles towards the pharynx away from the lungs. 

-The Lungs are enclosed in a double membrane known as the pleural membrane. One part of the membrane adheres tightly to the lungs and the other covers the inside of the thoracic cavity. The space between these membranes is known as the pleural cavity which is filled with pleural fluid which reduces friction during breathing.

-The Trachea branches into two bronchi (bronchus-singular), which divides into small tubes called bronchioles. Bronchioles branch and terminate in groups of tiny air sacs called alveoli ( singular alveolus).

Mechanism of breathing

-Breathing is accomplished by changes of the thoracic cavity in volume and air pressure.

-The Thoracic Cavity is enclosed by ribs which are attached to the vertebral column at the back and sternum at the front.

-The Ribs are covered by intercostal muscles and the diaphragm is below the cavity.

-Breathing mechanism involves two processes; inspiration (inhalation) and expiration (exhalation)

Inspiration/inhalation 

-External intercostal muscles contract while the internal intercostal muscles relax. This movement pulls the ribs upwards and outwards.

-The diaphragm which is dome-shaped flattens by the contraction of its muscles.

-These movements increase the volume of the thoracic cavity and decreases the pressure inside it.

-Atmospheric pressure being higher than the pressure inside the thoracic cavity, forces air to rush into the lungs. 

Expiration/exhalation 

-The external intercostal muscles relax while internal intercostal muscles contract bringing the ribs down to their original position.

-The muscles of the diaphragm relax and the diaphragm regains its original shape (dome-shaped)

-These movements decrease the volume of the thoracic cavity and increase the pressure inside it. Thus the air is forced out of the lungs through the air passages into the atmosphere.

1. Name the structures of the human respiratory system involved in breathing.

2. Describe the movements of the structures of the respiratory system and the changes in pressure and volume they bring about in the chest cavity during inspiration (inhalation).

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