Placental biology can be termed as the developmental biology of the Amniotic fluid and placenta.placenta can be defined as temporary organ joins the mother and fetus by tranferring nutrients and oxygen from mother to feutus and allowing relaease co2,waste products from feutus.The shape of placenta is disc shaped measuring seven inches in diameter and 2 inches thick with smooth upper surface and rough under surface.In general placenta are expelled during birth; together, these structures form the after birth. Journal Article is sometimes called a Scientific Article, a Peer-Reviewed Article, or a Scholarly Research Article. Together, journal articles in a particular field are often referred to as The Literature. Journal articles are most often Primary Research Articles. However, they can also be Review Articles. These types of articles have different aims and requirements. Sometimes, an article describes a new tool or method. Because articles in scientific journals are specific, meticulously cited and peer-reviewed, journal databases are the best place to look for information on previous research on your species.