. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 296 THE BRANCHIAL EPITHELIAL BODIES tion of the thyreoid body. It is situated immediately behind the anterior portion of the tongue, at the apex of the groove between this and the posterior portion, and is first a slight pouch-like depres- sion. As it deepens, its extremity becomes bilobed, and after the embryo has reached a length of 6 mm. it becomes completely sepa- rated from the floor of the pharynx. The point of its original origin is, however, permanently marked by a circular depression
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 296 THE BRANCHIAL EPITHELIAL BODIES tion of the thyreoid body. It is situated immediately behind the anterior portion of the tongue, at the apex of the groove between this and the posterior portion, and is first a slight pouch-like depres- sion. As it deepens, its extremity becomes bilobed, and after the embryo has reached a length of 6 mm. it becomes completely sepa- rated from the floor of the pharynx. The point of its original origin is, however, permanently marked by a circular depression, the foramen cacum (Fig. 175, fc). Later the bilobed body migrates down the neck and becomes a solid transversely elongated mass (Fig. 179, th), into the substance of which trabecule of connective tissue extend, dividing it into a network of anastomosing cords which. Fig. 179.—Reconstructions of the Branchial Epithelial Bodies of Embryos. of (a) 14 mm. and (b) 26 mm. ao, Aorta; Ith, lateral thyreoid; ph, pharynx; pth1 and pth2, parathyreoids; th, thyreoid; thy, thymus; vc, vena cava superior.—(Tourneux and Verdun.) later divide transversely to form follicles. When the embryo has reached a length of cm., a cylindrical outgrowth arises from the anterior surface of the mass, usually a little to the left of the median line, and extends up the neck a varying distance, forming, when it persists until adult life, the so-called pyramid of the thyreoid body. This account of the pyramid follows the statements made by recent workers on the question (Tourneux and Verdun); His has claimed that it is the remains of the stalk connecting the thyreoid with the floor of the pharynx, and which he terms the thyreo-glossal duct. Two other pairs of bodies enter into intimate relations with the. 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 resembl
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