Royal Army Medical Corps training pamphlet / War Office.

Date:
1944
Catalogue details

Licence: Public Domain Mark

Credit: Royal Army Medical Corps training pamphlet / War Office. Source: Wellcome Collection.

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    the movements of the ribs and diaphragm have been purposely exaggerated so as to show more clearly how the space occupied by the lungs enlarges on inspiration. At the end of inspiration the diaphragm relaxes and again arches upwards ; the muscles which raised the ribs and sternum cease to act, and the chest walls fall in. The cavity of the chest is.reduced in size, and air is consequently expelled from the lungs. As might be expected, however, the lungs are not completely emptied at each breath ; so only a proportion of the air is changed by a single respiration. 57. The voice.—The larynx contains muscular bands called vocal cords, and by contracting or relaxing these cords the size of the opening through the larynx can be varied at will, During normal respiration the passage of air through the larynx is silent ; but, with the cords in particular positions, particular sounds can be produced—yjust- as different notes can be whistled by blowing air through partly closed lips. In this way, expulsion of air from the lungs through the larynx produces the voice, which is further modified by the lips and tongue. CHAPTER. 7 DIGESTION 58. After being swallowed, most foods have to be digested before they can be taken into the blood. The process of digestion is carried out in the long tube called the alimentary canal. ‘The food is dissolved by juices which come from various digestive glands. The alimentary canal (Fig. 22) begins at the mouth and ends at the anus; it is about 30 feet long. Its main sections, from above downwards, are :— The mouth and throat. The gullet or cesophagus. The stomach. The small intestine. The large intestine. The glands or organs which pour juices into the alimentary canal are :— (a) The salivary glands. These secrete saliva, which is alkaline, into the mouth, where dipcstvon of the starchy parts of food begins.