The first sequences animate the development of the placenta as viewed under low magnification. The starting diagram shows the uterus with the endometrium in the secretory phase. Within the uterus is a 5-day-old blastocyst, which penetrates the endometrium and becomes fully implanted at the 9th day. The next sequence animates the growth of the blastocyst, which transforms into the chorionic vesicle in an approximately 21-day-old embryo. Besides the amniotic cavity and yolk sac, the diagram shows the chorionic villi, chorionic cavity, uterine cavity, somatopleuric- and splanchnopleuric mesoderms and other structures. The following sequence animates the growth of the embryo up to the 30th day. The chorionic villi transform into the placental villi and the chorionic plate, future chorion frondosums and chorion laeve become visible. In an approximately 8-week-old fetus, the chorion frondosum (i.e. future placenta and chorion laeve) are animated. Besides these structures, many other details are shown. The further growth of the fetus is animated up to an approximately 4.5-month-old fetus along with the full development of the placenta; amnion and chorion laeve comprise the amniochorionic membrane. The decidua parietalis and decidua capsularis fuse with the amniochorionic membrane to give rise to the fetal membranes.

The next sequences show the development of the placenta under high magnification. The first diagram depicts a uterus containing a 5-day-old blastocyst. As the 6-day-old blastocyst approaches the endometrium, it is framed, reoriented, and highly magnified. The diagram describes the structure of the functionalis of the endometrium in the second half of the secretory phase. The next sequence animates the beginning of implantation for a 7-day-old blastocyst. All structures of the blastocyst are described. The animation continues with a 9-day-old blastocyst, which is now fully within the endometrium. The maternal sinusoids and trophoblastic lacunae begin to connect.

This connection continues in an approximately 12.5-day-old blastocyst. The cytotrophoblastic proliferations appear at this time. In a 13-day-old blastocyst, the cytotrophoblastic proliferations develop into the primary chorionic villi. During the next two days, the primary chorionic villi transform into the secondary chorionic villi due to the penetration of a mesenchymal core into the primary chorionic villi. The formation of the intervillous spaces, which connect the stalks and other structures, is also animated. Over the course of the next three days, the outer cytotrophoblastic shell and tertiary chorionic form, revealing the placental villi. The embryonic blood vessels and the connecting stalk also appear.

Finally, in a 21-day-old embryo, the chorion frondosum and chorion laeve develop, and the placental stem villi begin to ramify.

The next sequence animates the development of the placental layers and the formation of a placental cotyledon.

With more than 15 legends, the starting diagram describes a uterus with an embryo at the end of the 3rd week. Three chorionic stem villi of the chorion frondosum are cut out, reoriented, and magnified. The diagram details more than 30 structures formed between the embryo and the mother, including the uteroplacental blood vessels. In a 4-month-old fetus, the stem villus branches out to form a cotyledon, and the decidual septa develop. The junction between the endometrium and the fetus also forms. Because of the complexity of these structural elements, two successive diagrams describe the newly created structures. The first presents a general view of the amniotic sac, chorionic plate lined with the amnion, and umbilical cord. The stem villus (i.e. cotyledon) and its connections with the junctional zone are detailed. Finally, the structure and stratification of the endometrium are explained. The next diagram, which contains more than 20 legends, reveals the layers that form between the embryo/fetus and the mother. The next sequence animates uteroplacental blood circulation. With the addition of a uteroplacental artery and two uteroplacental veins, the above-mentioned diagram depicts maternal circulation. The moving arrows symbolize blood circulation from the placental villi to the uteroplacental veins. The syncytiotrophoblastic islands break off and circulate through the intervillous spaces.

The next sequence animates fetal circulation through the umbilical arteries from the placental villi to the umbilical vein.

To show the transformation into a full-term placenta, the above-mentioned diagram is used again and labeled as a placenta in the second half of pregnancy. The cytotrophoblastic layer reduces in an approximately 7-month-old placenta, and the hypochorial (Langhans'), Rohr's, and inferior (Nitabuch's) fibrinoid bands appear between the fetus and the mother. The reduction of the cytotrophoblastic cells and accumulation of the fibrinoid in the above-cited bands is animated in a placenta at term.

The next sequences are dedicated to the evolution of the chorionic villi to the placental villi and the formation of the placental barrier as viewed under high magnification. The sequence starts with a 13-day-old blastocyst. The syncytio- and cytotrophoblast form the primary chorionic villi. One of these villi is sectioned, and the cut is surface magnified. The diagram shows the structure of a primary chorionic villus with a cytotrophoblastic core surrounded by the syncytiotrophoblast. Some cytological details are also described. In a 15-day-old chorionic villus, the mesenchymal core appears, and the primary chorionic villus becomes the secondary chorionic villus. Three days later, the blood vessels appear within the mesenchymal core, and the villus becomes the tertiary chorionic villus or placental villus of a young placenta. The basal lamina of the trophoblast and blood vessels, the Hofbauer cells, and syncytiotrophoblastic islands develop. On the diagram, the layers composing the placental barrier in a young placenta are illustrated. In an approximately 4-month-old placenta, the placental villi divide. The diagram shows two placental villi with identical structures. During the second half of pregnancy, in a full-term placenta, of the number of blood capillaries in the placental villi increases, while the number of cytotrophoblastic cells decreases. In addition, the capillaries approach the trophoblast, and the capillary basal lamina fuse with the trophoblastic lamina. The diagram illustrates the layers of the placental barrier in a full-term placenta.

The next sequence animates the separation of the placenta from the uterus. First, the delivery of a newborn is animated in mediosagittal section followed by the expulsion of the placenta. The diagram shows the empty uterine cavity with the placenta and umbilical cord. The uterus contracts, and the retroplacental hematoma forms. The retroplacental hematoma spreads, and the placenta separates from the uterus. The delivery of the placenta is also shown.

To show more precisely the above-mentioned events, a series of sequences is dedicated to the histology of the separation of the placenta from the uterus. The first diagram shows the histologic structure of a placenta immediately after childbirth. Then, in a shearing movement, the contraction of the myometrium cuts the uteroplacental blood vessels at the level of the Nitabuch's fibrinoid band followed by the spreading of the maternal blood between the basal layer of the endometrium and the decidua basalis. All of these events are animated. The next sequence shows the contraction of the cut uteroplacental arteries and the expulsion of the placenta from the uterus by the retroplacental hematoma. The last diagram of this sequence details the histologic structure of the endometrium remnants approximately 20 minutes after childbirth. The basal layer of the endometrium with stroma, basal portions of the uterine glands, basal arterioles, and interrupted radial arterioles and veins, all covered with maternal blood, overlies the myometrium.

The next sequence animates the regeneration of the endometrium. The first diagram of this sequence is the last one from the former sequence. The uterine glands, radial arterioles, and veins lengthen, and the stroma regenerates during the course of the puerperium. The spiral arterioles, capillary network, collecting lacunae and veins regenerate. The epithelium of the uterine glands covers the stroma, thus reestablishing the normal structure of the endometrium at the end of the puerperium.

The next sequence is dedicated to the function of the placenta. A sectioned placental villus with fetal blood vessels during the second half of pregnancy is shown. The diagram demonstrates the structure of the villus and indicates the position of the placental barrier. Then, a small area of the placental barrier is observed under a transmission electron microscope.

The capillary endothelium, fused capillary and trophoblastic basal laminae, and syncytitrophoblast studded with microvilli are shown. The next sequence details all substances, including viruses and parasites, that may cross the placental barrier from mother to the fetus or from fetus to mother.

To show the evolution of placental types, the next sequences animate the development of the epithelio-chorial, syndesmo-chorial, endothelio-chorial and haemo-chorial placentae.

Placenta previa (animated under Implantation) and erythroblastosis fetalis are described as malformations. The hydatidiform mole is animated as another malformation.

(This animation is essential for students of medicine, veterinary medicine, and biology as well as for departments of anatomy, histology, embryology, physiology, and cell biology; it is also recommended for students of stomatology, departments of obstetrics and gynecology, and schools for midwives.)