. Chordate morphology. Morphology (Animals); Chordata. In the male the medullary cords, infiltrated with germ cells, form the seminiferous tubules, while in the female the medullary cords are repressed. Clumps and strands of cor- tical cells, with germ cells among them, become partly en- closed by thin strands of medullary cells. The medullary strands supply thecal (encapsulating) cells to the cortical cords in which the nests of female germ cells develop. Late in development the ovary moves posteriorly below its peri- toneal cover. Its suspensory ligament marks this movement. It still remains
. Chordate morphology. Morphology (Animals); Chordata. In the male the medullary cords, infiltrated with germ cells, form the seminiferous tubules, while in the female the medullary cords are repressed. Clumps and strands of cor- tical cells, with germ cells among them, become partly en- closed by thin strands of medullary cells. The medullary strands supply thecal (encapsulating) cells to the cortical cords in which the nests of female germ cells develop. Late in development the ovary moves posteriorly below its peri- toneal cover. Its suspensory ligament marks this movement. It still remains in contact with the body wall, but the ovi- duct now loops below and in front of it (Figure 10-37). The MuUerian ducts form the tubular portion of the fe- male system, conducting the egg from the ovary, supplying it with the proper environment for its development (uterus), and aiding in fertilization by means of a copulatory pouch, the vagina. The Mullerian ducts appear relatively late (20 mm) in man and develop by a process of infolding, begin- ning at the anterior end of the mesonephros and extending posteriorly. It should be noted that the ostium of this tube lies well anterior to the genital part of the mesonephric kidney. The first evidence of this duct is a thickening of the epithelium of the kidney ne.\t to the nephric duct. This thickening forms a groove (Figure 35 A) which closes over, except at its anterior end, the ostium. This process of invagination and tubulation extends back along the kidney through the genitoinguinal fold to the midline anterior to the urogenital sinus. Here the two ducts unite and extend back to enter the urogenital sinus just in front of the neph- ric duct (see Figure 355, Patten, 1946). The genitoinguinal fold has been modified by the medial movement of the pos- terior end of the Mullerian ducts. From the anterior end of their fused area a fold now extends to the inguinal region, passes out through the inguinal canal, and ends in the labia m
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