5 Breathing

Definition of breathing – Breathing refers to the muscular contractions and movements of the ribs which result in air moving in and out of the lungs.

5.1 The Lungs

· 2 lungs – left and right lungs

· Located within the thoracic cavity, protected by the rib cage.

· Diaphragm is a layer of muscles that separates the thoracic from the abdominal cavity.

· Each lung is protected by a double membrane known as pleural membrane. Pleural fluid is present in between the two layers of the pleural membranes so as to reduce friction.

5.2 The Thoracic Cavity

· The chest wall is supported by 12 pairs of ribs. 10 pairs of ribs are attached to the font of the chest at the sternum (chest bone) and to the back of the chest at the vertebral column. The remaining two pairs of ribs are called the ‘floating ribs’ which only attach to the vertebral column and not the sternum.

· Two sets of muscles – the external intercostal muscles and internal intercostal muscles are found between the ribs. These two sets of muscles are antagonistic. Ie when the external intercostal muscles contract, the internal intercostal muscles relax.

5.3 Breathing mechanisms

2 main process of breathing:

1. Inhalation (Inspiration)

2. Exhalation (Expiration)

Youtube video on Breathing Mechanism. URL: http://www.youtube.com/watch?v=pc2MmhkUW_E Visited on 10 August 2013.

Stimulus for breathing

• High concentration of carbon dioxide in the blood is the stimulus for breathing.

5.5 Differences between inhaled and exhaled air

Table of differences between inhaled and exhaled air.