. Embryology. Embryology; Embryology; genealogy. STRUCTURE OF THE EMBRYO AT HATCHING 135 Thus the hypophysis of the embryo forms only the anterior lobe of the adult pituitary. Its function is extensive, and several hormones—including a growth- promoting hormone and two gonadotropic hormones—have been isolated and purified. On each side of the hypophysis are two blood vessels called the dorsal aortic roots. These vessels run forward as the internal carotid arteries and fuse posteriorly to form the dorsal aorta. In the early embryo the dorsal aortic roots connect with the ventral aortic roots by
. Embryology. Embryology; Embryology; genealogy. STRUCTURE OF THE EMBRYO AT HATCHING 135 Thus the hypophysis of the embryo forms only the anterior lobe of the adult pituitary. Its function is extensive, and several hormones—including a growth- promoting hormone and two gonadotropic hormones—have been isolated and purified. On each side of the hypophysis are two blood vessels called the dorsal aortic roots. These vessels run forward as the internal carotid arteries and fuse posteriorly to form the dorsal aorta. In the early embryo the dorsal aortic roots connect with the ventral aortic roots by means of the aortic arches (see Fig. 78). Ventral to the hypophysis lies the pharynx, lined with endoderm. From the floor of the pharynx an outgrowth (oral evagination) is directed toward an ingrowth of the epidermis (stomodeum). These two pockets fuse, and an opening forms the mouth. The oral suckers are purely embryonic and larval structures; they degenerate soon after the larva begins to feed. ANTERIOR CARDINAL VEIN DORSAL AORTA EFFERENT ARTERY RHOMBENCEPHALON ENDOLYMPHATIC DUCT NERVE GANGLION. AORTIC ARC AFFERENT ARTERY VENTRAL AORTA PERICARDIUM HEART Fig. 78. The structures present in a cross section through the otocysts. The heart and blood vessels are shown in schematic form, since actual sections do not show how the blood circulates from the heart through the external 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 Barth, Lester G. (Lester George), 1905-1979. New York, Dryden Press
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