1144 



DIGESTIVE SYSTEM 



irregularly folded omentum are exposed the coils of the small intestine; in the right 

 iliac fossa a part of the csecum appears; and in the left iliac fossa the lower (iliac) 

 part of the descending colon and the beginning of the sigmoid colon. 



To the left of the stomach and under cover of the lower ribs of the left side the 

 edge of the spleen may possibly be observed; and just below the edge of the liver, 

 and about the level of the tip of the ninth rib, the gall-bladder may be seen. The 

 dome of the urinary bladder may be noticed just behind the symphysis pubis and 

 in the median line. The disposition of the viscera in the foetus is shown in fig. 953. 



General morphology — Before taking up the various individual organs included in the 

 abdominal and pelvic portions of the alimentary canal, a brief consideration of their general 

 morphology is desirable. The primitive canal, as already described in the embryo (in the 



Fig. 900. — Digrammatic Representation of an Early Stage in the Development of 

 THE Alimentary Canal and the Peritoneum. (After Sobotta-McMurrich.) 



Lesser curvature (Esophagus 



Ventral mesogastrium \ ^^ Stomach 



(lesser omentum) \ ^,«.^g^=.^y Greater curvature 



Ventral mesogas- 

 trium (falciform 

 lig.) 



Liver 



Falciform lig. 



Umbilical vein 



Omphalo-mesenteric du 



Umbilical aa 



Spleen 

 Aorta 



Left gastric art. 



Dorsal meso- 

 y gastrium 



Splenic art. 



Pancreas 



Coeliac art. 

 Mesenterium 

 commune 



Sup. mesenteric art. 



Left colic flexure 



Inf. mesenteric art. 



Descending meso- 

 colon 



Cloaca 



t 



Distal limb of intestinal loop 



section on Morphogenesis), and as found in the lower vertebrates is a comparatively straight, 

 simple tube extending ventral to the body axis from mouth to anus. In the abdominal region 

 (and primitively throughout the whole trunk), the canal lies within tlie body cavity, which is 

 lined by parietal perit(Hieum. The visceral peritoneum is reflected from the mid-dorsal line 

 as a double layer, the jtriniitivc dorsdl rnc.srnlcry, within which the vessels and nerves pass to 

 the walls of the canal. Within the; dorsnl mesentery are also the spleen and pancreas. In 

 the anterior (uj)per) region of the abdomen there is also a similar primitive ventral mesentery, 

 which contains the liver. 



The relations above mentioned are indicated diagrammatically in fig. 900, which represents 

 a comparatively early stage in the development of the intestinal canal. The liver is already 

 almost completely separated from the diaphragm (with which it was intimately associated in 

 the earlier septum transversum). The ventral mesentery persists in the form of (1) the gastro- 



