. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE EXTERNAL GENITALIA 363 The Development of the External Genitalia.—At about the fifth week, before the urogenital sinus has opened to the exterior, the mesenchyme on its ventral wall begins to thicken, producing a slight projection to the exterior. This eminence, which is known as the genital tubercle (Fig. 219, gt), rapidly increases in size, its extremity becomes somewhat bulbously enlarged (Fig. 221, gl) and a groove, extending to the base of the terminal enlargement, appears upon its v
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE EXTERNAL GENITALIA 363 The Development of the External Genitalia.—At about the fifth week, before the urogenital sinus has opened to the exterior, the mesenchyme on its ventral wall begins to thicken, producing a slight projection to the exterior. This eminence, which is known as the genital tubercle (Fig. 219, gt), rapidly increases in size, its extremity becomes somewhat bulbously enlarged (Fig. 221, gl) and a groove, extending to the base of the terminal enlargement, appears upon its vestibular surface, the lips of the groove forming two well- marked genital folds (Fig. 221, gf). At about the tenth week there appears on either side of the tubercle an enlargement termed the genital swelling (Fig. 221, gs), which is due to a thickening of the mesenchyme of the lower part of the ventral^abdominal wall in the V^. Fig. 221.—The External Genitalia of an Embryo of 25 mm. a, Anus; gf, genital fold; gl, glans; gs, genital swelling; p, perineal body.—(Keibel.) region where the inguinal ligament is attached, and with the appear- ance of these structures the indifferent stage of the external genitals is completed. In the female the growth of the genital tubercle proceeds rather slowly and it becomes transformed into the clitoris, the genital folds becoming prolonged to form the labia minora. The genital swellings increase in size, their mesenchyme becomes transformed into a mass of adipose and fibrous tissue and they become converted into the labia majora, the interval between them constituting the vulva. In the male the early stages of development are closely similar to. 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 McMurrich, J. Playfair (James Playfair), 1859-1939. Philadelphia : P. Blakis
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Keywords: ., bookautho, bookcentury1900, bookdecade1910, booksubjectembryology
