THE ANATOMY OF A SIX MM. PIG EMBRYO 



denum, and, in the course of the right vitelline vein, passing between the 

 dorsal and ventral pancreas to the right of the duodenum, it soon enters the 

 liver and connects with the liver sinusoids. The portal trunk is thus 

 formed by persisting portions of both vitelline veins, and receives a new 

 vessel, the superior mesenteric vein. The middle portions of the primitive 



Int. car- Ant. car- 

 Metencephalon otid artery dinal vein 

 P.I 



Thyreoid Ph. P. 2 



Mesencephalon 



Ventral aorta 



Ophthalmic 

 vein 



Myelencephalon 

 Ph. P. 3 



Notochord 



Descending aorta 



Ph. P. 4 



Pulmonary artery 

 Linguo-facial 



Intersegmental 

 vein 



Spinal cord 



Mesonephros 



Post, cardinal vein Mesonephric arteries 



FIG. 104. Reconstruction of 7.8 mm. pig embryo, showing veins and aortic arches from the left 

 side (after Thyng). X 15. Ph.P. 1, 2, 3, 4, Pharyngeal pouches. 



vitelline veins are connected with the network of liver sinusoids. Their 

 proximal vitelline trunks drain the blood from the liver and open into the 

 sinus venosus of the heart. The right member of this pair is much the 

 larger (Fig. 100) and persists as the proximal portion of the inferior vena 

 cava. For the development of the portal vein see Chapter IX. 



