What do placental villi contain

By the second month, the vascular core has develope At term, large vessels follow the villous core up to the basal plate, and these vascular trunks in the anchoring villi give rise to the capillary networks which are involved in all branches of the villi THE VILLUS AFTER MONTH 4 After 4 months, the villus is richly vascular and has a thin coat as a result of the disappearance of the cytotrophoblast contrast with the villus of 2 months The placenta at term may show a few large, persistent cytotrophoblastic areas particularly on the maternal plate , but, as term nears, the cytotrophoblast vanishes in this region as well and is replaced by a fibrinoid layer As a result of numerous branchings, the villus has become comparable to a "bushy tre" Its branches form a tangled mass in whose meshes the maternal blood circulates.

Related Organs. Related Anatomical Compartments. The placental membrane separates maternal blood from fetal blood. The fetal part of the placenta is known as the chorion. The maternal component of the placenta is known as the decidua basalis.

Although the placental membrane is often referred to as the placental barrier , many substances, both helpful and harmful, can cross it to affect the developing embryo. These blood vessels connect up with vessels that develop in the chorion and connecting stalk and begin to circulate embryonic blood about the third week of development. Figure 4 - Structure of placenta and chorionic villi. Table 8 - Substances that Cross the Placental Membrane.

Glucose, amino acids, free fatty acids, vitamins. Carbon dioxide, urea, uric acid, bilirubin, creatine, creatinine. Fetal and maternal both a few. Maternal serum proteins.

Serum albumin, some protein hormones thyroxin, insulin. Steroid hormones. This layer is divided into two further layers: the underlying cytotrophoblast layer and the overlying syncytiotrophoblast layer. The latter is a multinucleated, continuous cell layer that covers the surface of the placenta. It forms as a result of the differentiation and fusion of the underlying cytotrophoblast cells, a process that continues throughout placental development.

The syncytiotrophoblast otherwise known as syncytium thereby contributes to the barrier function of the placenta. Placenta : Image illustrating the placenta and chorionic villi. The umbilical cord is seen connected to the fetus and the placenta.

Learning Objectives Summarize the development of the chorionic villi and placenta. Key Points Chorionic villi invade and destroy the uterine decidua while at the same time they absorb nutritive materials from it to support the growth of the embryo. The villi begin primary development in the fourth week, becoming fully vascularized between the fifth and sixth weeks.

Placental development begins with implantation of the blastocyst; this leads to its differentiation into several layers that allow nutrient, gas, and waste exchange to the developing embryo and fetus —as well as forming a protective barrier.

The ST14 has been implicated in several cellular events, such as epithelial migration, remodeling of the extracellular matrix, cell differentiation, and oncogenesis in epithelial cancers [ 30 ]. The results from Spint1- knockout mice indicate that SPINT1 plays an important role in the early stage of placental development. Thus, SPINT1 expression and synthesis likely occur throughout the human chorionic villous tree during late gestation.

The HGF stimulates the branching morphogenesis of human villous CTB [ 39 , 40 ] and human placental angiogenesis [ 40 ]. Taking all these findings into consideration, we hypothesize that the structural integrity of the SPINT1-positive CTB layer plays an important role in regulating the efficient localization and concentration of HGF activators on and around the basal surface of the CTB layer. This function of the inhibitor allows villous differentiation and maintenance of the chorionic villous tree via the HGF signaling system during gestation.

Recently, SPINT1 was found to be a potent inhibitor not only of the HGF activators described above but also of PRSS8, a glycosylphosphatidylinositol-anchored serine protease that is highly expressed in human and mouse placentas [ 31 , 41 ] Fig. In human airway epithelium, PRSS8 activates epithelial sodium channels [ 42 ], although its physiologic functions in the placenta remain unclear. Another aspect of the present study was the shape transformation of CTB cells.

As a component of the placental barrier, this property is germane to the mechanism of fetomaternal exchange. Changes in the placental barrier, in the form of a decrease in the thickness and number of layers, occur in parallel with villous differentiation. As noted above, the CTB layer has been considered to play a reduced role in maintaining the placental barrier during late gestation; however, the present results suggest that the extremely thin layer of CTB cells is involved in barrier maintenance.

It should be emphasized that we do not interpret our findings as evidence for the complete interruption of communication between the STB layer and fetal endothelium by the CTB layer during late gestation. The initially cuboidal-shaped CTB cells are transformed to flat cells with many long cellular processes that, together with those of STB, eventually cover the trophoblast basal lamina in a complex network of interdigitations.

This unique structural change of the basal domain of the trophoblast layer may be involved in the regulation of molecular transport for fetomaternal exchange, an important function of the placental barrier. Although our data challenge currently held ideas about the morphogenesis of the CTB layer in human placenta, the functional roles of this layer during late gestation remains to be elucidated. In this context, it would be of interest to use SPINT1, as a specific marker, to examine the CTB in pathological conditions that affect villous development and vascular morphogenesis, such as intrauterine growth retardation and preeclampsia.

These types of experiments should be carried out concomitantly with conditional knockout studies in animal models. Further studies in our laboratories are aimed at investigating the physiologic functions of the CTB in late gestation. We also are indebted to Drs. Clark L. Pathology of the Human Placenta , 5th ed. New York : Springer ; : 50 — Sadler TW. Langman's Medical Embryology , 9th ed.

From 13 weeks to term, the trophoblast of human placenta grows by the continuous recruitment of new proliferative units: a study of nuclear number using the dissector. Placenta ; 13 : — Google Scholar. Hepatocyte growth factor activator inhibitor, a novel Kunitz-type serine protease inhibitor.

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