Sem1mini2 - Placental Development

Human chorionic gonadotropin (hCG) is the hormone first produced by the syncytiotrophoblast cells of the early placenta to maintain the viability of the corpus luteum. This hormone plays a crucial role in early pregnancy by stimulating the corpus luteum to continue producing progesterone, which is essential for maintaining the uterine lining and supporting the pregnancy. hCG levels can be detected in the blood or urine to confirm pregnancy, as its production begins shortly after implantation of the fertilized egg in the uterus.

During early pregnancy, most drugs are transported across the placental barrier primarily by simple diffusion. This is because simple diffusion is a passive process that allows molecules to move from an area of higher concentration to an area of lower concentration. The placental barrier is a selectively permeable membrane that allows small molecules, such as drugs, to pass through easily. Since simple diffusion does not require energy or specific carrier proteins, it is the most common method of drug transport across the placenta.

IgG is the correct answer because it is the only immunoglobulin that can cross the placental barrier. This allows for passive immunity to be transferred from the mother to the fetus, providing protection against certain infections. IgA, hormones from the pituitary gland, maternal cholesterol, and maternal phospholipids do not cross the placental barrier.

During Stage 3 of labor, the placenta separates at the spongy layer of the decidua basalis. This layer is located in the uterus and is responsible for anchoring the placenta to the uterine wall. As the placenta detaches, the spongy layer of the decidua basalis is shed, allowing the placenta to be expelled from the uterus. This separation is a natural part of the third stage of labor and is necessary for the completion of the birthing process.

Triglycerides are too large and insoluble in water to cross the placental barrier. The placental barrier allows for the exchange of certain substances between the mother and fetus, but it is selective in what it allows to pass through. Cortisol, amino acids, glucose, and IgG can all cross the placental barrier, but triglycerides cannot.

The allantois is a structure that develops during embryogenesis and is responsible for the formation of the umbilical arteries and vein. It is an outpouching of the hindgut and is involved in the exchange of gases and waste products between the embryo and the mother. The umbilical arteries carry deoxygenated blood from the fetus to the placenta, while the umbilical vein carries oxygenated blood from the placenta to the fetus.

During the final stages of fetal development, the placental barrier is composed of syncytiotrophoblast and endothelial cells of fetal capillaries. The syncytiotrophoblast is responsible for nutrient and gas exchange between the mother and the fetus, while the endothelial cells of fetal capillaries help in the transport of oxygen and nutrients from the placenta to the fetus. This combination of syncytiotrophoblast and endothelial cells ensures proper exchange of substances and supports the growth and development of the fetus.

Syncytiotrophoblast cells are involved in the production of placental estrogen. These cells are a specialized layer of cells that form the outermost layer of the placenta. They play a crucial role in hormone production during pregnancy, including the production of estrogen. Estrogen is important for maintaining pregnancy, promoting fetal development, and preparing the mother's body for childbirth. Therefore, the correct answer is Syncytiotrophoblast.

The most oxygenated blood flows to supply the fetus through the aorta. The aorta is the main artery that carries oxygen-rich blood from the heart to the rest of the body, including the placenta, where the exchange of oxygen and nutrients takes place between the mother and the fetus. From the placenta, the oxygenated blood is then transported to the fetus through the umbilical vein. Therefore, the aorta is the correct answer as it carries the oxygenated blood to nourish the developing fetus.

Lateral folding is the correct answer because ectopia cordis or Pentalogy of Cantrell is a congenital malformation of the anterior body wall, which is formed during the process of lateral folding in embryonic development. Lateral folding involves the folding of the embryo's sides towards the midline, resulting in the formation of the body wall and the closure of the ventral body wall. In the case of ectopia cordis, the failure of proper lateral folding leads to the heart being positioned outside the chest cavity.

After the twentieth week of gestation, the placental membrane is thinned and consists of three layers: syncytiotrophoblast, connective tissue of the villus, and fetal capillary endothelium. This arrangement allows for efficient exchange of nutrients and waste products between the maternal and fetal circulations. The syncytiotrophoblast layer is responsible for nutrient transfer and hormone production, while the connective tissue of the villus provides structural support. The fetal capillary endothelium allows for the exchange of gases and other substances between the maternal and fetal blood.

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The absence of a ventral double-fold of coelomic membrane connecting the heart to the ventral body wall (a ventral mesocardium) is a result of a bilateral connection of the early intraembryonic coelom rostral to the developing heart.