الفهرس Only 14 pages are availabe for public view
 |  | from | 172 |  |  |
| | | from | 172 | | |
Abstract
The placenta is defined as the fusion of foetal membranes with the uterine mucosa for the purpose of materno fetal exchange of nutrients, gases, and waste substrates. According to this definition, placental development starts at day 6 or 7 post-conception, as soon as the blastocyst starts invasion of the endometrium.
The placenta is responsible for the nutritive, respiratory, and excretory functions of the fetus. The placenta is often overlooked in the routine evaluation of a normal gestation, receiving attention only when an abnormality is detected.
In this study, the imaging characteristics of the normal and abnormal human placenta are presented.
In this study, after reviewing the embryologic features of the placenta, normal placental anatomy and morphology are described, including twin gestations. Finally, pathologic conditions of the placenta, including placental causes of hemorrhage, gestational trophoblastic disease, nontrophoblastic placental tumors, metastases, and cystic lesions are discussed.
Typically, the placenta is located along the anterior or posterior uterine wall, extending onto the lateral walls. Although usually discoid, the placenta can be variable in morphology. Variant placental shapes include bilobed, succenturiate, circumvallate, and placenta membranacea.
Circumvallate placenta is caused when the fetal surface presents a central depression surrounded by a thickened ring, composed of a double fold of amnion and chorion with degenerated decidua and fibrin in between.