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7417248 
Journal Article 
Fertilization and Implantation 
Mutlu, L; Macer, M; Taylor, HS; , 
2013 
Springer New York 
New York, NY 
Clinical Reproductive Medicine and Surgery 
75-90 
Knowledge of fertilization and implantation is essential for understanding both normal reproduction and the pathological basis of infertility. The purpose of this chapter is to discuss our current understanding of normal fertilization and implantation. A healthy spermatozoon is essential for reproduction and must undergo a variety of changes in order to fertilize an oocyte. Spermatogenesis occurs in the seminiferous tubules of the testes and is controlled by the affect of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) on testicular Sertoli and Leydig cells. Mature spermatozoa are then transported through the epididymis, combined with seminal vesicle and prostatic secretions, and ultimately transported into the vaginal vault with ejaculation. Through a calcium-mediated process called capacitation, the spermatozoon develop hypermotile flagella and an activated acrosome, eventually resulting in penetration of an oocyte. Normal oogenesis and folliculogenesis are crucial in order to produce a healthy oocyte for fertilization. Following menarche, release of FSH and LH stimulates development of antral follicles, completion of meiosis, and subsequent ovulation of a dominant follicle. An activated spermatozoon binds to the outer layer of the oocyte, the zona pellucid, and fertilization by a single spermatozoa ensues. With completion of a second meiotic division, and genomic union of the sperm and oocyte, a zygote forms. Approximately day 6 or 7 post-ovulation, the trophoectoderm of the blastocyst implants into the endometrial epithelium. Many factors are required for successful implantation. In addition to proper trophoblast development and invasion, endometrial receptivity has been shown to be crucial for normal implantation, and disruption of it a major cause of abnormal placentation and infertility. Due to the complexity of fertilization and implantation, it is not surprising that two of the most common mechanisms of infertility are failure of fertilization and failure of implantation.