________________
Human Body
73
The Nose
The nose is the gateway to the respiratory tract. It filters, warms and moistens the incoming air. Nostrils and the area just inside are lined with a picket-fence of short stiff hairs. This is the first line of defence, screening large particles out of the entering air. The interior of the nasal cavity is lined with mucous membrane. Dust and other fine particles and bacteria are caught in the sticky mucus. The mucous membrane also helps to moisten the incoming air. It also contains dense vascular plexus (with copious blood supply) which acts as a radiator to warm the air. The jutting shelves--turbinates-increase the radiating surface making the warming action more effective.
It is also possible to breathe through the mouth but the mouth is not supplied with the apparatus for cleaning, warming and moistening the air. Mouth-breatbing, therefore, must be avoided. The Pharynx and the Larynx
The pharynx is an important junction for the passageways leading into the body. Both air and food have to pass through it. The passage connecting the pharynx with the trachea is called larynx or 'voice-box'. Its main function is the production of speech. But it is also important in breathing and protecting the trachea from foreign objects. The epiglottis is a hinged 'trap door' at the entrance of the larynx. During swallowing it closes like a lid to prevent the entry of food into the trachea, "The Trachea, the Bronchi and the Bronchioles
The trachea or windpipe is a cylindrical tube about 11 cms. long and about 2 to 2.5 cms in diameter. It lies in front of the aesophagus. Its tubular walls are reinforced by C-shaped rings of cartilage. It divides into two branchesbronchi, one leading into each lung. It is also lined with mucus-secreting cells. Inhaled particles are trapped in the mucus. The cilia (fine hairs) in the lining of the trachea and bronchi whisk up the dust laden mucus upwards towards the pharynx where they can be expectorated. The trachea with its two branches-the bronchi and their numerous branches the bronchial tubes and bronchioles, looks very
Jain Education International
For Private & Personal Use Only
www.jainelibrary.org
