Full-term placenta

ORIENTATION IN THE SLIDE

A part of the placenta that is visible in the slide includes the basal plate (in an interactive slide indicated in blue), which represents the maternal part. An outer part of the basal plate looks straight as it is cut off the myometrium. An inner part is facing the intervillous space; it is a site where anchoring villi are inserted. The principal chorionic villi are relatively large, and they can be found in longitudinal or transverse sections. Villi ramify extensively and tiny terminal villi almost completely fill in the intervillous space.  Some chorionic villi are labelled in light green colour; two of them are anchored to the basal plate (the so called anchoring villi). The intervillous space also contains the decidual (placental) septa (purple) emanating from the decidua basalis.

Fig. 2. Interactive slide of the full-term placenta: Survey. Description can be found in the text. Stained with haematoxylin and eosin.
Author of the microphotograph: J. Mokrý.

INTERVILLOUS SPACE AND CHORIONIC VILLI

Intervillous space left among chorionic villi is narrow; it contains the maternal blood, which is removed from the slide in the course of tissue fixation - as a result only few red blood cells can be seen here. Chorionic villi are labelled in an interactive Fig. 3 in green. A detailed structure of chorionic villi and placental septa is depicted in Figs. 4 and 5. A surface of chorionic villi is covered by many deposits of the fibrinoid (orange) of different sizes (some are tiny, but others can cover several villi).

Fig. 3. Interactive slide of the inner side of the full-term placenta: Middle magnification. Moving a cursor to an image shows structures in the slide in different colours. Illustration legend can be found in the text; stained with haematoxylin and eosin.
Author of the microphotograph: J. Mokrý.

Placental or decidual septum belongs to the maternal part of the placenta as it is derived from the decidua basalis. Like other structures of the basal plate, this septum also contains decidual cells. Decidual cells are relatively large and of polygonal or oval shape. Some decidual cells in Fig. 5 are lined by a black colour; oval nuclei are grey, they often contain the nucleolus. A surface of the septum can be also covered by the fibrinoid (orange). Next to the septum the chorionic villi can be seen (two villi are indicated in green). Cleft-like space left between the villi, the so called intervillous space (indicated by letter "I") is filled in with the maternal blood. The foetal blood occurs in the blood capillaries inside of the chorionic villi.

Fig. 4. Interactive slide of the placental setum in  the full-term placenta: Detail. Moving a cursor to an image shows structures in the slide in different colours. Illustration legend can be found in the text.
Author of the microphotograph: J. Mokrý.

CHORIONIC VILLUS OF THE FULL TERM PLACENTA

Chorionic villus in the mature placenta can be distinguished from the villus of the early placenta in a transverse section. An outer surface is covered by the continuous syncytiotrophoblast (in an interactive slide it is indicated in dark green colour). Cytotrophoblast is reduced so that single cells (five cells are indicated in light green). A connective tissue of the villus contains many blood capillaries (red) that reach the edges of the villi - some contact the syncytiotrophoblast. Inside of blood capillaries, foetal blood cells can be seen; the maternal blood occurs in the intervillous space.

Fig. 5. Interactive slide of the chorionic villus in of the full-term placenta: Detail. Moving a cursor to an image shows structures in the slide in different colours. Illustration legend can be found in the text.
Author of the microphotograph: J. Mokrý.