Fertilization of the Oocyte Fertilization occurs when the chromosomes of the oocyte and the sperm unite to produce a zygote, the first cell of a new cell individual.

Basic information Sperm cell (23 chromosomes) and the oocyte (23 chromosomes) are both consider to be a haploid because they contain half of the genes from each parent. Once they combine a zygote forms, which is also called a diploid ,because it is a full set from the sperm and oocyte. A Zygote contains 46 chromosomes. An ovulated oocyte can live up to 24 hours without being fertilized. Sperm can live up to 5 days in the female reproduction tract. For fertilization to be successful, intercourse must occur no more than two days before ovulation and no more than 24 hours after. The oocyte if present should be in the distal third of the uterine tube.

Capacitation of the sperm Most of the sperm will not make it to the oocyte because they either get lost along the way ,stuck or the leak out of the vagina. Sperm can make the journey of 10 to 15 centimeters within 5 to 10 minutes. Sperm requires 10 hours in the female reproductive system for capacitation. Capacitation is the process by which sperm is able to penetrate and fertilize an oocyte. There is a protective cap(acrosomal enzymes) on the sperm that breaks down as it is traveling through the female reproductive system by the female fluids.it has to break down before entering the oocyte.

Brief summary When the 1st sperm gets to the oocyte membrane, the sperm and the oocyte membrane fuse. This fusion triggers oocyte activation. The oocyte activation involves a serious of chemical changes in the oocyte , including a polyspermy block and the completion of meiosis II. The polyspermy block is put up so it can stop more sperm from fertilizing with the egg.

Fusion Once the sperm fuses with the oocytes membrane, it triggers the completion of meiosis II. Once meiosis II is completed, the oocytes nuclear material reorganizes to form a structure called pronucleus. The oocyte is now called an ovum and is ready to combine its DNA with the sperm. As this is happening the sperms DNA is doing the same thing. Once both have finished , the pronuclei move toward the center of the ovum, where they find each other and fuse together. This allows their DNA to combine and fertilization is complete.

Video http://www.babycentre.co.uk/v1049102/inside-pregnancy-fertilisation-video