Spermatozoon structure Spermatozoon is shaped like a tadpole, with a total length of about 66 μm, and is divided into two parts: the head and the tail. The head is oval in shape on the front and pear-shaped on the side, and contains a nucleus with very dense chromatin and an acrosome. The sperm acrosome is a structure unique to sperm cells. The human sperm acrosome is located at the anterior end of the sperm head, covering the front of the sperm nucleus, and consists of the acrosomal cap and the equatorial plate, which is a membrane-bound cap-like structure. The acrosome contains a variety of protein hydrolases and phosphatases. The process of fertilization Sperm enters the reproductive tract and begins the process of capacitation when it crosses the cervix. When the capacitated sperm passes through the extracellular matrix of the oocyte mound, it is activated to trigger the acrosome reaction, which releases enzymes within the acrosome. The acrosomal enzymes dissolve the radial crown of the oocyte and the zona pellucida, and sperm are able to enter the oocyte successfully, completing the process of fertilization. Only after spermatozoa are energized and acrosome occurs can they penetrate into the egg cell and fuse with it to complete fertilization. Significance of inducing sperm acrosome reaction The acrosome reaction is one of the key steps in the process of sperm fertilization. One of the reasons why the egg cannot be fertilized is that the spermatozoa bound to the zona pellucida of the oocyte cannot undergo the acrosome reaction, and therefore the spermatozoa cannot penetrate the zona pellucida of the oocyte and enter into the egg. Clinically, it is sometimes found that the wife of a man with abnormal semen routine analysis can conceive normally, while a small number of men with normal semen routine analysis may also have low fertilization rate or even complete failure of fertilization after routine in vitro fertilization. Routine semen analysis can not fully reflect the ability of sperm fertilization, and induced sperm acrosome reaction rate test can make up for its shortcomings.