THE ANATOMY OF A SIX MM. PIG EMBRYO 



I0 3 



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 olid artery dinal vein 



lyreoid Ph. P. 2 



Mesenccphalon 



Ventral aorta 



Ophthalmic 

 vein 



Myelenrephalon 

 Ph. P. 3 



Duetus vena 



R. umbilical vein 



R. ventricle 



L. com. cardinal win 



Liver 



,Notochord 



Descending aorta 



Ph. P. 4 



Pulmonary artery 

 Lingua-facial 

 MM 

 R. com. 

 cardinal vein 



Sinus venosns 



.Com. hepatic 

 vein 



Post, car- 

 dinal vein 



R. subclavian 

 vein 



R. subcar- 

 dinal vein 



Pulmonary 

 vein 



Intersegmental 



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, S, 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. 



