AC 2.3 THE PHASES OF A DEVELOPING EMBRYO An embryo is a developing fetus, this development process lasts 8 weeks and is called the embryonic phase. An embryo turns into a fetus after the eighth week of development. Below is a table showing the weekly development of the embryo.AC 2.4 THE ROLE OF THE PLACENTATA THE PLACENTAThe placenta is an organ that is attached to the uterine mucosa during pregnancy. The placenta begins its development with the implantation of the blastocyst in the mother's uterine lining. It connects to the fetus via the umbilical cord and resembles a piece of liver with its reddish-brown hue and fleshy-looking exterior. It is usually delivered after the baby is born through the combination of hormone release and contractions. The contractions help separate the placenta from the wall of the uterus. The placenta is approximately 9 inches long at delivery and weighs 1/6 of the baby's weight. In multiple births, babies share the placenta but have individual umbilical cords. THE ROLE OF THE PLACENTA1. The placenta provides the baby with adequate nutrition, glucose, minerals, vitamins and amino acids. The placenta also allows the diffusion of these substances.2. The placenta produces hormones such as estrogen and progesterone, which have the ability to prevent premature contractions before the baby is born and prepare the uterus for labor, the placenta also produces a hormone called placental lactogen, which allows the mother to have more glucose in circulation to provide your baby.3. The placenta serves as a protective barrier, ensuring that disease-causing microorganisms cannot reach the baby.4. The placenta acts as an effective filter keeping maternal blood separate... center of paper......Pregnant [online] Available from [Accessed January 15, 2014]ChildBirthGraphics.com (2012) Hormones in labor and birth [online] Available from [Accessed 15 January 2014]Hub Pages Inc. (2014) Hormones involved in lactation and milk supply [online] Available from [Accessed 15 January 2014]Jarvis, S., Stone, J., Eddleman , K. , Duenwald, M., (2005) Pregnancy For Dummies UK ed. Chichester: John Wiley & Sons Ltd.Parker, S., (2013) The Book of the Human Body 2nd ed. London: Dorling Kindersley Ltd.Walker, R., (2003) Guide to the Human Body. London: Octopus Publishing Group Ltd.Wright, D., (2007) Human Physiology and Health. Revised ed. Oxford: Cambridge Publishing Management Ltd.