130 ORGANS OF DIGESTION. 



and gives attachment to the great omentum. The surfaces of the organ are 

 limited by these two curvatures. 



The anterior surface is directed upwards and forwards, and is in relation with 

 the Diaphragm, the under surface of the left lobe of the liver, and with the 

 abdominal parietes, in the epigastric region. 



The posterior surface is directed downwards and backwards, and is in relation 

 with the pancreas and great vessels of the abdomen, the crura of the Diaphragm 

 and the solar plexus. 



The stomach is held in position by the lesser omentum, which extends from 

 the transverse fissure of the liver to its lesser curvature, and by a fold of peri- 

 toneum, which passes from the Diaphragm on to the cesophageal end of the 

 stomach, the gastro-phrenic ligament; this constitutes the most fixed point of 

 the stomach, whilst the pyloric end and greater curvature are the most movable 

 parts: hence, when the stomach becomes greatly distended, the greater curva- 

 ture is directed forwards, whilst the anterior and posterior surfaces are directed, 

 the former upwards, and the latter downwards. 



Alterations in Position. There is no organ in the body the position and connections of which 

 present such frequent alterations as the stomach. During inspiration, it is displaced downwards 

 by the descent of the Diaphragm, and elevated by the pressure of the abdominal muscles during 

 expiration. Its position in relation to the surrounding viscera is also changed, according to the 

 empty or distended state of the organ. When empty, it occupies only a small part of the left 

 hypochondriac region, the spleen lying behind it ; the left lobe of the liver covers it in front, and 

 the under surface of the 'heart rests upon it above, and in front; being separated from it by the 

 left lobe of the liver, besides the diaphragm and pericardium. This close relation between the 

 stomach and the heart explains the fact that, in gastralgia, the pain is generally referred to the 

 heart, and is often accompanied by palpitation and intermission of the pulse. When the stomach 

 is distended the Diaphragm is forced upwards, contracting the cavity of the chest; hence the 

 dyspnoea complained of, from inspiration being impeded. The heart is also displaced upwards ; 

 hence the oppression in this region, and the palpitation experienced in extreme distension of 

 the stomach. Pressure from without, as from tight lacing, pushes the stomach down towards 

 the pelvis. In disease, also, the position and connections of the organ may be greatly changed, 

 from the accumulation of fluid in the chest or abdomen, or from alteration in size of any of the 

 surrounding viscera. 



On looking into the pyloric end of the stomach, the mucous membrane is 

 found projecting inwards in the form of a circular fold, the pylorus, leaving a 

 narrow circular aperture, about half an inch in diameter, by which the stomach 

 communicates with the duodenum. 



The pylorus is formed by a reduplication of the mucous membrane of the 

 stomach, containing numerous muscular fibres, which are aggregated into a 

 thick circular ring, the longitudinal fibres and serous membrane being con- 

 tinued over the fold without assisting in its formation. The aperture is occa- 

 sionally oval. Sometimes, the circular fold is replaced by two crescentic folds, 

 placed, one above, and the other below, the pyloric orifice ; and, more rarely, 

 there is only one crescentic fold. 



Structure. The stomach consists of four coats: a serous, a muscular, a cellu- 

 lar, and a mucous coat, together with vessels and nerves. 



The serous coat is derived from the peritoneum, and covers the entire surface 

 of the organ, excepting along the greater and lesser curvatures, at the points 

 of attachment of the greater and lesser omenta; here the two layers of peri- 

 toneum leave a small triangular space, along which the nutrient vessels and 

 nerves pass. 



The muscular coat (Fig. 399) is situated immediately beneath the serous 

 covering. It consists of three sets of fibres: longitudinal, circular, and oblique. 



The longitudinal fibres are most superficial ; they are continuous with the 

 longitudinal fibres of the oesophagus, radiating in a stellate manner from the 

 cardiac orifice. They are most distinct along the curvatures, especially the 

 lesser; but are very thinly distributed over the surfaces. At the pyloric end, 

 they are more thickly distributed, and continuous with the longitudinal fibres 

 of the small intestine. 



The circular fibres form a uniform layer over the whole extent of the stomach, 



