Index Introduction Page 3Secision and blastulation Page 5Morula and blastocyst Page 6Implantation and placentation Page 7Placentation Page 8Formation of the three primary germ layers Page 9Embryonic acquisition of the external form Page 11IntroductionBeginning of pregnancy: another A new individual is formed when the components of a powerful sperm combine with those of a fertile egg. Various motile spermatozoa are saved in the vagina, pass through the uterus and attack the uterine (Fallopian) tubes, where they incorporate the egg. After entering the tube, the egg loses its outer layer of cells due to the activity of substances present in the sperm and the lining of the tubal wall. The loss of the outer layer of the egg allows various sperm to enter the surface of the egg. However, one and only sperm regularly transforms into the healing creature. When it has entered the substance of the ovum, the atomic leader of this spermatozoon differentiates from its tail. The tail continually disappears, but the head with its nucleus survives. As it reaches the center of the ovule (at this stage called the female pronucleus), the head expands and transforms into the male pronucleus. The two pronuclei successively approach each other, meet halfway through the egg's cytoplasm, and lose their nuclear membranes. Each resolves its diffuse chromatin material into a single complete set of 23 chromosomes. Centrioles apparently supplied by the sperm appear and a mitotic spindle organizes itself with the two sets of chromosomes arranged halfway on it, ready to proceed with a typical mitosis in fertilization events creates a joint product called a zygote Contains all the factors essential for the development of...... middle of paper ......ædia Britannica Retrieved from http://www.britannica .com/EBchecked/topic/275660/human-embryology6- Nazario, B. (2013, WebMD - Better information.. Healthy Babies: Worth the Wait). /www.webmd.com/baby/pregnancy-137- Nordqvist, C. (2009, June 4) Medical news today: the latest health news. What is pregnancy? How do I know if I'm pregnant? - Medical news today. Retrieved May 2, 2014, from http://www.medicalnewstoday.com/articles/38302.php8- Pregnancy. (2011). In the Encyclopedia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/474704/pregnancy9- Teresa, A., &Jaquez, M. (2012). Pregnancy (Vol.6). New York: Nova Science.10- University of Rochester Medical Center, (n.d.). Women's health. Retrieved May 1, 2014, from http://www.stronghealth.com/services/womenshealth/maternity/trimesters.cfm