THE FCETAL CIRCULATION 



695 



FCETAL CIRCULATION 



The changes which accompany the transformation of the foetal type of 

 circulation into that of the adult are initiated by the first inspiration. Prior to 

 this act the functions of external respiration and digestion are performed by the 



Fig. 546. — The Heart, with the Arch op the Aorta, the Pulmonary Artery, the 



Ductus Arteriosus, and the Vessels concerned in the Fcetal Circulation. 



(From a preparation of a fcetus in the Museum of St. Bartholomew's Hospital.) 



Right innominate vein 



Superior vena cava 



Right pulmonary artery 



Inferior vena cava 



Left branch of portal vein 

 Ductus venosus 



Umbilical vein 

 Portal vein 



Right branch of 

 portal vein 



Umbilical vein 

 Umbilical arteries 



Umbilical artery 



Left innominate 

 vein 



Arch of aorta 

 Ductus arteriosus 

 .Left pulmonary 

 artery 



Descending aorta 



Superior 

 mesenteric artery 



Splenic vein 

 Superior 

 mesenteric vein 



Inferior 

 mesenteric artery 



•Left common iliac 

 artery 



Hypogastric artery 

 External iliac artery 



mother; the foetal venous blood passing to the placenta through the umbilical 

 arteries and returning through the umbilical vein. 



At the time of birth the right and left chambers of the heart communicate 

 only by means of an oblique passage between the overlapping atrial septa (p. 511). 

 The pulmonary artery and descending aorta communicate by means of the 

 ductus arteriosus (p. 508). 



i 



