Author
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Bakst, Murray |
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Submitted to: Journal of Experimental Zoology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/7/1998 Publication Date: N/A Citation: N/A Interpretive Summary: A consequence of continued genetic selection for heavier birds by the commercial poultry industry is the negative impact this practice has on hen fertility. Knowledge of the biological mechanisms regulating fertile egg production is necessary to successfully address this problem. The macroanatomy, histology, and fine structure of the avian oviduct is reviewed and related to its role in fertile egg production. The avian oviduct functions as a biological assembly line, beginning sequentially with the deposition of the albumen around the fertilized or unfertilized ovum, then the shell membrane, and lastly, the shell all within 25 hr of ovulation. While in transit through the oviduct, the fertilized ovum progresses to the pre-gastrulation stage of development. New observations on the structure of the oviductal sperm storage sites are also introduced. These observations provide fundamental information for scientists to seeking to improve the reproductive efficiency of poultry. Technical Abstract: This review will address the role of the oviduct in the reproductive strategy of the bird, with emphasis placed on poultry. Five anatomically and functionally distinct segments are discernable, which in craniocaudal order are the infundibulum (grasps ovulated ovum and is the site of fertilization), magnum (albumen synthesis), isthmus (shell membrane formation), shell gland (uterus), and vagina (sperm storage site). The secreted proteinaceous materials are products of the luminal surface epithelium and subepithelial tubular glands found in each of these segments. Abovarian transport of the egg is accomplished by contraction of smooth muscle and possibly the activity of the dorsal and ventral ligaments. Alternatively, adovarian transport of sperm appears to be primarily accomplished by ciliary activity. After semen deposition, sperm are subjected to an intense selection process orchestrated by the vagina. "Selected" sperm enter the sperm-storage tubules, which are tubular invaginations localized at the cranial aspect of the vagina. Here sperm reside until exiting and ascending to the site of fertilization. If fertilized, the first cleavage furrow is evident in 6-8 h, while the egg mass is in the isthmus or shell gland. The role of oviductal secretions relative to the oviducal phase of embryonic development has yet to be investigated in birds. |
