. A laboratory manual and text-book of embryology. Embryology. i,Common CQrclina-l V€l Lv/lelline vein Left ventricle - R. vitelline vein _/? Ventricle Fig. -Dorsal and caudal view of the heart from a 6 mm. pig embryo. X 21. Bulbus cor^ In Fig. 96, from a slightly smaller embryo, it is seen that the septum primum grows from the dorsal atrial wall of the heart and does not yet meet the endocardial cushions between the atrio-ventricular canals. This opening between the atria is known as the interatrial foramen. Before it closes, another opening appears in the septum, dorsal in positio
. A laboratory manual and text-book of embryology. Embryology. i,Common CQrclina-l V€l Lv/lelline vein Left ventricle - R. vitelline vein _/? Ventricle Fig. -Dorsal and caudal view of the heart from a 6 mm. pig embryo. X 21. Bulbus cor^ In Fig. 96, from a slightly smaller embryo, it is seen that the septum primum grows from the dorsal atrial wall of the heart and does not yet meet the endocardial cushions between the atrio-ventricular canals. This opening between the atria is known as the interatrial foramen. Before it closes, another opening appears in the septum, dorsal in position. This is the foramen ovale and persists during fetal life. In Fig. 96 these two openings may be seen, as may also the dorsal and ventral endo- cardial cushions. The outer mesothelial layer of the ventricles has become much thicker than that of the atria. It forms the epicardium and the myocardium, the sponge-like meshes of which are now being developed. The arteries begin with the ventral aorta, which takes origin from the bulbus cordis. From the ventral aorta are given off five pairs of aortic arches. These run dorsad in the five branchial arches (Figs. 99 and 100) and join the paired dorsal or descending aortce. The first and second pairs of aortic arches are very small and take origin from the small common trunks formed by the bifurcation. foramen ovaJe WallofLaJrium Infer atria I foramen ..Endocardial Cushions Fig. 96.—Dissection of a mm. pig's heart from the left side, showing the septum primum and two interatrial foramina. X Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Prentiss, Charles William, 1874-1915. Philadelphia, London, W. B. Saunders
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
