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ShareThe placenta is an ephemeral (temporary) organ present only in female placental vertebrates during gestation (pregnancy).
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All mammals other than monotremes and (most) marsupials utilise placentas in reproduction, and are known as placental mammals.
Also, some species of snakes utilise placentas. The placenta is composed of two parts, one of which is genetically and biologically part of the fetus, the other part of the mother.
It is implanted in the wall of the uterus, where it receives nutrients and oxygen from the mother's blood and passes out waste.
This interface forms a barrier, the placental barrier, which filters out some substances which could harm the fetus.
However, many other substances are not filtered out, including alcohol and some chemicals associated with smoking cigarettes.
Several types of viruses, such as Human Cytomegalovirus, may also cross this barrier; this often leads to various degrees of birth defects in the infant.
The placenta is connected to the fetus via the umbilical cord, which is composed of blood vessels and connective tissue.
When the fetus is delivered, the placenta is delivered afterwards (and for this reason is often called the afterbirth).
For more information about the topic Placenta, read the full article at Wikipedia.org, or see the following related articles:
Umbilical cord — In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to its placenta. It contains one or two major vessels, ... > read more
Fetus — A fetus (also foetus) is a developing mammal after the embryonic stage and before birth. The plural is fetuses or foetuses. In humans, a fetus ... > read more
Birth weight — Birth weight is the weight of a baby at its birth. It has direct links with the gestational age at which the child was born and can be estimated ... > read more
Pregnancy — Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. In a pregnancy, there can be ... > read more
Progesterone — Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other ... > read more
Mammalian embryogenesis — Mammalian embryogenesis is the process of cell division and cellular differentiation which leads to the development of a mammalian embryo. A mammal ... > read more
Breech birth — A breech birth (also known as breech presentation) refers to the position of the baby in the uterus such that it will be delivered buttocks first as ... > read more
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
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