Hair and Scalp Slideshow
Slideshow: The Amazing Journey of Conception From Egg to EmbryoMore Slideshows from eMedicineHealthWatch and learn from these additional pictures slideshows. Infectious Mononucleosis Slideshow Vegetarian Diet Slideshow Swine Flu Slideshow Eye Diseases See All Slideshows Conception: From egg to embryoAt the moment when a lone sperm penetrates a mature egg, conception or fertilization takes place. To better understand the incredible process of conception, take a journey with us from tiny egg to growing embryo. OvulationEach month, a mature egg is released from one of the women's two ovaries -- this is called ovulation. Ovulation takes place about two weeks after the first day of the last menstrual period. The rare picture shown here is the clearest ever taken of human ovulation. Observing ovulation in humans is extremely rare, and previous images have been fuzzy. Passage into the fallopian tubeOnce the egg is released from the ovary, it travels into the fallopian tube where it remains until a single sperm penetrates it during fertilization. The laborious journey of the spermAn average ejaculate discharges 40-150 million sperm which eagerly swim upstream toward the fallopian tubes on their mission to fertilize an egg. Fast-swimming sperm can reach the egg in a half an hour, while other may take days. The sperm can live up to 48-72 hours. Only a few hundred will even come close to the egg, due to the many natural barriers and hurdles that exist in the female reproductive tract. Fertilization: Sperm penetrates eggIf a sperm cell meets and penetrates an egg, it will fertilize the egg. The fertilization process takes about 24 hours. When fertilization happens, changes occur on the surface of the egg to prevent other sperm from penetrating it. At the moment of fertilization, the genetic makeup is complete, including the sex of the infant. The cells begin to divideThe fertilized egg begins dividing rapidly, growing into many cells. It leaves the fallopian tube and enters the uterus three to four days after fertilization. Rarely, the fertilized egg does not leave the fallopian tube; this is called a tubal pregnancy or ectopic pregnancy and is a danger to the mother. ImplantationAfter entering the uterus, the fertilized egg attaches to the uterine lining, or endometrium. This process is called implantation. The cells continue to divide. Pregnancy hormonesHuman chorionic gonadotropin (hCG) is a hormone present in the blood within about a week of conception. It is the hormone detected in a blood or urine pregnancy test, but it usually takes three to four weeks for levels of hCG to be high enough to be detected by pregnancy tests. It is secreted by cells that develop into the placenta. Fetal developmentAfter implantation, some cells become the placenta while others become the embryo. About three weeks after ovulation, the baby's brain, spinal cord, heart, and others organs begin to form. The heart begins beating during week five. During week seven, the umbilical cord appears. At the eighth week the developing baby, now called a fetus, is well over 1/2 of an inch long -- and growing. A 'full term' delivery generally occurs around 40 weeks. More Reading on Conception and PregnancyAdvertisementReviewed by Brunilda Nazario, MD on March 04, 2008 WebMD Medical Reference: "Pregnancy: Understanding Conception." WebMD Medical Reference: "Your Pregnancy Week by Week: Weeks 1-4." WebMD Medical Reference: "Genetics: Topic Overview." WebMD Medical Reference from "The Fertility Sourcebook:" "The Semen Factor." "A Child is Born," Lennart Nilsson, Lars Hamberger. Mayo Clinic web site. Images provided by Phototake: Copyright © Dennis Kunkel / Phototake -- All rights reserved. Getty: Stone/Yorgos Nikas, Visuals Unlimited/Dr. David M. Phillips, Photonica/Steven Puetzer, 3D4Medical.com. PhotoTake: Courtesy of the film, Building Babies. (c) Mona Lisa., Copyright © LookatSciences / Phototake -- All rights reserved. , Copyright © Dr. Y. Nikas / Phototake -- All rights reserved.
This tool does not provide medical advice. See additional information: THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the eMedicineHealth Site. If you think you may have a medical emergency, immediately call your doctor or dial 911. © 2008 WebMD, LLC. All rights reserved. |









