. Cunningham's Text-book of anatomy. Anatomy. 1034 THE VASCULAE SYSTEM. The perforations eventually blend together to form the secondary foramen ovale of the inter- atrial septum. As soon as the septum primum is completed the primitive atrium is divided into the permanent right and left atria, each of which communicates through the secondary foramen ovale, with the atrium of the Left part of atrio-ventricular orifice Truncus arteriosus opposite side and with the Septum primum fusing with corresponding portion of the ventricle through an atrio- ventricular aperture which is completely separate
. Cunningham's Text-book of anatomy. Anatomy. 1034 THE VASCULAE SYSTEM. The perforations eventually blend together to form the secondary foramen ovale of the inter- atrial septum. As soon as the septum primum is completed the primitive atrium is divided into the permanent right and left atria, each of which communicates through the secondary foramen ovale, with the atrium of the Left part of atrio-ventricular orifice Truncus arteriosus opposite side and with the Septum primum fusing with corresponding portion of the ventricle through an atrio- ventricular aperture which is completely separate from its fellow of the opposite side. As the ventral border of the septum primum fuses with the endocardial cushions of the atrio - ventricular canal, the septum secundum appears im- mediately to the right of the septum primum. It grows from the dorsal and cephalic (superior in adult) walls of the atrium. As the septum secun- dum develops, the right cornu of the sinus venosus is ab- sorbed into the atrium, the left venous valve fuses with the septum primum or dis- appears, and the angle between the right horn and the inter - Fig. 831.—View op the Interiors of the Right and Left Atria of mediate part of the sinus ap- a Human Embryo 5'5 mm. long. (Edinburgh University collection, pears in the caudal part of the Modelled by C. C. Wang.) dorsal wall of the right atrium. As the septum secundum in- creases in size its cephalic part grows first ventrally and then caudally and lastly dorsally; conse- quently the free border soon becomes concave and the concavity of its margin is directed dorsally. Both extremities of the free margin of the septum secundum fuse with the right lateral surface of the septum primum, and the more ventrally situated part of the border, growing along the. Wall of right atrium Septum primum fusing with inferior atrio- ventricular cushion Septum primum Left venous valve Right - venous valve Inferior atrio- ventricular cushion Bight posterior cardinal veins op
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
