182 



THE ENTODERMAL CANAL AND THE BODY CAVITIES 



nective tissue. The parietal lining is derived from the somatic layer of 

 mesoderm and the visceral covering from the splanchnic layer. 



Esophagus 



Pericardial cavity 

 Ventricle of heart 



Ventral mesocardium 

 Liver _ 



Ventral mesentery 

 (falciform ligament) 



Dorsal mesocar- 

 dium 



Septum transversum 



Stomach 



B 



Ventral mesentery 



(lesser amentum) 



Dorsal mesogastrium 



Dorsal pancreas 



Mesorectum 



FIG. 189. Diagram showing the primitive mesenteries of an early human embryo in 

 median sagittal section. The broken lines (A , B, and C) indicate the level of sections A , B, 

 and C, in Fig. 190. 



Neural lube 



Aorta Notochord 



Postcar- 4 . 

 dinalvein Aori 

 Dorsal mesentery. 



Fore-gut 



Lesser 



amentum 



Liver 



Peritoneal 



cavity 

 Falciform 

 ligament 



FIG. 190. Diagrammatic transverse sections of an early human embryo. A, Through 

 the heart and pericardial cavities; B, through the fore-gut and liver; C, through the intestine 

 and peritoneal cavity. 



The primitive ccelom lies in the horizontal plane, as in Fig.iSS. Coin- 

 cident with the caudal regression of the septum transversum, the peri- 

 cardial cavity is bent ventrad and enlarged (Fig. 191). The ventral 



