The development of the human body; a manual of human embryology . necessarily somewhat differentfrom what obtains in the child after birth. Taking theplacenta as the starting-point, the blood passes along theumbilical vein to enter the body of the fetus at the umbili-cus, whence it passes forward in the free edge of the ante-rior mesentery (see p. 340) until it reaches the liver. Here,owing to the anastomoses between the umbilical andomphalomesenteric veins, a portion of the blood traversesthe substance of the liver to open by the hepatic veins intothe inferior vena cava, while the remainder p
The development of the human body; a manual of human embryology . necessarily somewhat differentfrom what obtains in the child after birth. Taking theplacenta as the starting-point, the blood passes along theumbilical vein to enter the body of the fetus at the umbili-cus, whence it passes forward in the free edge of the ante-rior mesentery (see p. 340) until it reaches the liver. Here,owing to the anastomoses between the umbilical andomphalomesenteric veins, a portion of the blood traversesthe substance of the liver to open by the hepatic veins intothe inferior vena cava, while the remainder passes onthrough the ductus venosus to the cava, the united streamsopening into the right auricle. This blood, whose purityis only slightly reduced by mixture with the blood re-turning from the inferior vena cava, is prevented frompassing into the right ventricle by the Eustachian valve, THE FETAL CIRCULATION. 289 which directs it to the foramen ovale, and through this itpasses into the left auricle, thence to the left ventricle, andso out by the systemic ypu Fig. 152.—The Fetal , Aorta; , pulmonary artery; au, umbilical artery; da, ductusarteriosus; dv, ductus venosus; int, intestine; vci and vcs, inferiorand superior vena cava; vh, hepatic vein; vp, vena porta;; ,pulmonary vein; vu, umbilical vein.—{From Kallmann.) The blood which has been sent to the head, neck, andupper extremities is returned by the superior vena cavaalso into the right auricle, but this descending stream 29O THE DEVELOPMENT OF THE HUMAN BODY. opens into the auricle to the right of the annulus of Vieus-sens (see Fig. 131) and passes directly to the right ventri-cle without mingling to any great extent with the bloodreturning by way of the inferior cava. From the rightventricle this blood passes out by the pulmonary artery,but the lungs at this period are collapsed and in no condi-tion to receive any great amount of blood, and so thestream passes by way of the ductus
Size: 1268px × 1970px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
