What is Placenta?
[[File:Placenta.svg|thumb|230px|Plancenta in womb diagram]] [[File:Placenta held.jpg|thumb|A placenta with umbilical cord attached]] The '''placenta''' is a temporary [[Organ (anatomy)|organ]] in the [[uterus]] (womb) of [[Pregnancy|pregnant]] female [[mammal]]s. Its main role is to transfer oxygen and nutrients from the mother's blood to the baby's blood, and to transfer waste molecules back from the baby's blood to the mother's. It also protects the baby from harmful substances in the mother's blood, and produces [[Hormone|hormones]] that support the pregnancy. The placenta is attached to the wall of the uterus and connected to the baby by big blood vessels in the [[umbilical cord]]. After the baby [[Childbirth|is]] born, the placenta and cord are also pushed out of the uterus. At this time the placenta and cord are often called the '''afterbirth'''. == Functions == === The placenta feeds the baby and removes its wastes === The baby in the womb gets everything it needs through the placenta. Oxygen travels in the mother's blood from her lungs to the placenta and then in the baby's blood through the umbilical cord to the baby. [[Carbon dioxide]] waste travels the same route in reverse, from the baby's blood to the mothers blood and out through her lungs. Nutrient molecules (sugars, fats, proteins and vitamins) travel through her blood from her digestive tract to the placenta, and then in the baby's blood to the baby, and waste products travel back to her kidneys for disposal. === The placenta protects the mother and fetus === One of the placenta's jobs is to make sure [[blood]] from the mother and fetus never mixes. The placenta acts as an [[exchange]] surface between the mother and the fetus. [[Nutrient]]s and [[oxygen]] are passed from one bloodstream to the other by [[diffusion]] only. If the mother's and fetus's blood mixed, it could be deadly for both of them. If the mother and the fetus had different [[w:blood type|blood types]], they might both die if their blood mixed. === The placental ba