The Defence Mechanisms Peculiar to the Alimentary Tube

THE defence mechanisms peculiar to the alimentary tube itself are very limited. For analytical purposes they may be considered under the already mentioned broad classification of mechanical and chemical types of assault. Mechanical Assault.—The most easily investigated response to a harmful stimulus is a modification of the muscular activity of the wall of the tube. Since the only stimulus capable of evoking visceral pain is stretching leading to an exaggerated muscular activity, visceral pain of […]

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The Significance of Alimentary Pain

FROM the clinical aspect one of the most important evidences of the presence of abnormal conditions in the alimentary tube is a complaint of pain in, or in the neighbourhood of, the tube. The interpretation of such pain has given rise to much controversy, and in the following summary it must be appreciated that many of the views presented are not universally accepted. A brief definition of the nature of pain may help in the […]

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The Relevant Features of the Controlling Nervous Mechanism

THE important part played by the neuromuscular apparatus in defence, and the prominence allotted by modern theories to a nervous element in the causation of many clinical conditions in the alimentary tube, render it essential that the nervous arrangements of the tube should be studied carefully. In an elementary manual it is.impossible to discuss these in much detail, but a brief outline of the factors involved may indicate the lines of further study. The various […]

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The Work of the Explusive Segments

Compartment V, the last of the three great abdominal compartments of the alimentary tube, is almost entirely expulsive. No digestive processes are carried on in any part of this compartment; the chemical reactions taking place in it are chiefly of a bacterial nature. There is prob- ably some absorption of water from the pelvic colon, but no absorption of foodstuffs. Muscular activity is directed to driving the contents of the tube distalwards to the rectum […]

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The Work of the Final Digestive and Absorptive Segments

Compartment IV is the final digestive and absorptive chamber of the alimentary tube, and its vital centre is the distal half of the duodenum and the whole of the jejunum. From its situation this compartment is very difficult to investigate. Materials introduced into it, either from above or below, have had to traverse long stretches of the alimentary tube before reaching it, and may be completely altered in composition before arriving. Changes taking place in […]

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The Work of the Preparatory Segments

THE contents of Compartment I are under voluntary selection and voluntary control. Many considerations may be in- volved in making a selection from the materials offered before food is actually taken into the mouth. After the materials chosen have entered the mouth a further selection is possible. T h e chief factors in the final selection are the taste-buds (flavours), the teeth, and the muscular walls (consistence). The substances ultimately selected are then subjected to […]

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The General Anatomical Disposition of the Abdominal Part of the Alimentary Tube

THE original conception of an arrangement of the various parts of the abdominal alimentary tube within fixed ana- tomical boundaries, was completely disproved when it became possible to obtain radioscopie views of the alimentary tube in the living subject. From these it was apparent that only a few regions of the bowel could be regarded as even relatively fixed; the variations in position of the other parts were extremely marked. The relatively fixed regions are: […]

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The Lining Membrane of the Alimentary Tube

THE most prominent feature of the mucous membrane lining the alimentary tube is the great collection of glands related to it. The majority of these glands are embedded in the membrane. They are small (microscopic) single tubes lined by secretory cells and opening directly on the free surface of the mucous membrane. The material secreted may be of a simple nature as in the mucous glands, but in other glands, e.g., seromucous glands, certain stomach […]

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The Nervous Arrangements of the Alimentary Tube

THE muscles of Compartment I and of the upper part of Com- partment II as far as the junction of the upper and middle thirds of the oesophagus are chiefly striated muscles and are innervated mainly by somatic nerves; the glandular struc- tures of these compartments are, however, associated with the autonomic system. The part of the alimentary tube from the lower two-thirds of the oesophagus to the anal canal is activated almost entirely by involuntary […]

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The Vascular Arrangements of the Alimentary Tube

Arteries.—In Compartments I and II there are no special points of clinical interest in connexion with the arterial arrangements. The arteries are derived from those supplying structures in the vicinity. In the remainder of the alimentary tube, i.e., the abdominal part, the distribution of the arteries is highly specialized. This accords with the observation that when the distribution of the branches o f a large artery is confined to a particular region, that region is […]

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