chorionic villi

Examples of chorionic villi in the following topics:

• Chorionic Villi and Placental Development

  • In the placenta, chorionic villi develop to maximize surface-area contact with the maternal blood for nutrient and gas exchange.
  • Chorionic villi sprout from the chorion after their rapid proliferation in order to give a maximum area of contact with the maternal blood.
  • During the primary stage (the end of fourth week), the chorionic villi are small, nonvascular, and contain only the trophoblast.
  • Chorionic villi are vital in pregnancy from a histomorphologic perspective and are, by definition, products of conception.
  • Image illustrating the placenta and chorionic villi.

• Implantation

  • The syncytiotrophoblast then implants the blastocyst into the endometrium of the uterus by forming finger-like projections into the uterine wall called chorionic villi.
  • The chorionic villi grow outwards until they come into contact with the maternal blood supply.
  • The chorionic villi will be the border between maternal and fetal blood during the pregnancy, and the location of gas and nutrient exchange between the fetus and the mother.
  • The creation of chorionic villi is assisted by hydrolytic enzymes that erode the uterine epithelium.
  • During implantation, extensions of the trophoblast, the syncytiotrophoblasts, embed within the endometrium and form chorionic villi.

• Development of the Extraembryonic Coelom

  • It is the fetal aspect of the placenta that gives rise to chorionic villi.
  • Villi emerge from the chorion, which invade the endometrium, destroy the uterine decidua, and allow the transfer of nutrients from maternal blood to fetal blood.
  • Chorionic villi are at first small and nonvascular, and consist of only trophoblast, but they increase in size and branch.
  • Blood is carried to the villi by the paired umbilical arteries, which branch into chorionic arteries and enter the chorionic villi as cotyledon arteries.
  • Until about the end of the second month of pregnancy, the villi cover the entire chorion, and are almost uniform in size; but, after this stage, they develop unequally.

• Fourth Week of Development

  • The chorion undergoes rapid proliferation and forms numerous processes.
  • The chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo.
  • Until about the end of the second month of pregnancy the villi cover the entire chorion, and are almost uniform in size, but after this they develop unequally.

• Trophoblast Development

  • Cytotrophoblast in the tips of villi can differentiate into another type of trophoblast called the extravillous trophoblast.

• Histology of the Small Intestine

  • The intestinal villi are part of the mucosa.
  • Intestinal villi (singular: villus) are tiny, finger-like projections that protrude from the epithelial lining of the mucosa.
  • Villi increase the internal surface area of the intestinal walls.
  • An increased absorptive area is useful because digested nutrients (including sugars and amino acids) pass into the villi, which is semi-permeable, through diffusion, which is effective only at short distances.
  • The villi are connected to blood vessels that carry the nutrients away in the circulating blood.

• Anatomy of the Small Intestine

  • The epithelial cells which line these villi possess even larger numbers of microvilli.
  • The villi in the jejunum are much longer than in the duodenum or ileum.
  • The wall itself is made up of folds, each of which has many tiny finger-like projections known as villi on its surface.
  • The villi contain large numbers of capillaries that take the amino acids and glucose produced by digestion to the hepatic portal vein and the liver.
  • Lacteals are the small lymph vessels that are present in villi.

• Absorption in the Small Intestine

  • From the plicae circulares project microscopic finger-like pieces of tissue called villi (Latin for "shaggy hair") .
  • The function of the plicae circulares, the villi and the microvilli is to increase the amount of surface area available for the absorption of nutrients.
  • The epithelial cells of the villi transport nutrients from the lumen of the intestine into these capillaries (amino acids and carbohydrates) and lacteals (lipids).

• Early Pregnancy Tests

  • ., human chorionic gonadotropin (hCG).
  • The first of these markers to be discovered, human chorionic gonadotropin (hCG), is produced by the trophoblast cells of the fertilized ovum (blastocyst).
  • Most chemical tests for pregnancy look for the presence of the beta subunit of hCG or human chorionic gonadotropin in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to 12 days after fertilization.

• Amnion Development

  • Outside the amniotic ectoderm is a thin layer of mesoderm (continuous with that of the somatopleure), which is connected by the body stalk with the mesodermal lining of the chorion.
  • This fluid increases in quantity, causing the amnion to expand and ultimately to adhere to the inner surface of the chorion so that the extra-embryonic part of the coelom is obliterated.