Gamete and Zygote Transport
2014; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-12-397175-3.00005-3
Autores Tópico(s)Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities
ResumoRegulation of transport of gametes and early embryos through the female tract is crucial to successful reproduction; however, there is a great deal of variation among species with regard to the details of transport. Basically, sperm are deposited into the anterior vagina or uterus. Those deposited in the vagina swim through the cervix or are drawn through by uterine contractions. Muscular contractions assist in moving sperm through the uterine cavity. When sperm reach the entrance to the uterotubal junction, they are required to have certain cell surface proteins in order to enter. While still within the junction, or upon reaching the oviductal isthmus, sperm are trapped by binding to the mucosal epithelium, forming a storage reservoir. As the time of ovulation approaches, sperm become capacitated, which enables them to release from the epithelium and escape from the reservoir shortly before oocytes, usually surrounded by cumulus, are released from the ovary. The cumulus mass adheres lightly to cilia on the mucosal surface of the fimbria and the enclosed oocytes are thereby transported by ciliary action through the oviductal ampulla. During this time, a few sperm reach the cumulus mass to fertilize the oocytes. After pausing at fertilization, the embryo resumes transport, probably by the actions of smooth muscle in the oviductal wall, and reaches the uterus in a few days.
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