mesoderm

Examples of mesoderm in the following topics:

• Somite Development

  • Somites develop from the paraxial mesoderm and participate in the facilitation of multiple developmental processes.
  • During the second week of development the lateral mesoderm splits into a dorsal somatic mesoderm (somatopleure) and a ventral splanchnic mesoderm (splanchnopleure).
  • The mesoderm found lateral to the neural tube is called the paraxial mesoderm.
  • The paraxial mesoderm is initially called the unsegmented mesoderm in vertebrates, but is called the segmented mesoderm in chick embryos.
  • The dermatome is the dorsal portion of the paraxial mesoderm somite.

• Development of the Urinary System

  • The urinary system develops from the intermediate mesoderm during prenatal development.
  • The urogenital system arises during the fourth week of development from urogenital ridges in the intermediate mesoderm on each side of the primitive aorta.
  • It develops from the uteric bud, an outgrowth of the mesonephric duct, and the metanephric mesoderm, derived from the caudal part of the nephrogenic ridge.
  • The connective tissue and smooth muscle surrounding the bladder are derived from adjacent splanchnic mesoderm.
  • Intermediate mesenchyme or intermediate mesoderm is a type of embryological tissue called "mesoderm" that is located between the paraxial mesoderm and the lateral plate.

• Development of the Extraembryonic Coelom

  • During the formation of the primitive yolk sac, some of the migrating hypoblast cells transdifferentiate into mesenchymal cells that fill the space between Heuser's membrane and the trophoblast to form the extra-embryonic mesoderm.
  • As development progresses, small lacunae begin to form within the extra-embryonic mesoderm that become larger and form the extra-embryonic coelom.
  • The extra-embryonic mesoderm is divided into two layers: the extra-embryonic splanchnopleuric mesoderm, which lies adjacent to Heuser's membrane around the outside of the primitive yolk sac; and the extra-embryonic somatopleuric mesoderm, which lies adjacent to the cytotrophoblast layer of the embryo.
  • The chorionic plate is composed of an inner layer of somatopleuric mesoderm and an outer layer of trophoblast cells.
  • It consists of an extra-embryonic mesoderm and two layers of trophoblast and surrounds the embryo and other membranes.

• Development of the Integumentary System

  • The integumentary system develops from all embryonic layers (ectoderm, mesoderm, and neural crest cells).
  • Fetal skin forms from three layers: ectoderm, mesoderm, and neural crest cells.
  • Between 4 and 12 weeks, the basal cells divide repeatedly to form the stratified epithelium while the mesoderm forms the blood vessels and connective tissues.

• Tissue Development

  • The epiblast keeps moving and forms a second layer, the mesoderm.
  • The mesoderm germ layer forms in the embryos of triploblastic animals.
  • The formation of a mesoderm leads to the development of a coelom, a fluid filled cavity.
  • Image illustrates the types of cells produced by the mesoderm (middle germ layer) of the developing embryo.
  • Compare the three embryonic germ layers (endoderm, mesoderm, and ectoderm) from which all body tissues develop

• Gastrulation

  • During gastrulation, the embryo develops three germ layers (endoderm, mesoderm, and ectoderm) that differentiate into distinct tissues.
  • These three germ layers are known as the ectoderm, mesoderm, and endoderm.
  • The mesoderm is found between the ectoderm and the endoderm, giving rise to somites.
  • The differentiation of cells into one of three types (endodermal, mesodermal, or ectodermal).

• Neurulation

  • Following gastrulation, the neurulation process develops the neural tube in the ectoderm, above the notochord of the mesoderm.
  • During gastrulation cells migrate to the interior of the embryo, forming the three germ layers: the endoderm (the deepest layer), the mesoderm (the middle layer), and the ectoderm (the surface layer) from which all tissues and organs will arise.
  • In a simplified way, it can be said that the ectoderm gives rise to skin and the nervous system, the endoderm to the intestinal organs, and the mesoderm to the rest of the organs.
  • After gastrulation, the notochord—a flexible, rod-shaped body that runs along the back of the embryo—is formed from the mesoderm.

• Chorionic Villi and Placental Development

  • During the secondary stage (the fifth week), the villi increase in size and ramify, while the mesoderm grows into them; at this point the villi contain trophoblast and mesoderm.
  • During the tertiary stage (fifth to sixth week), the branches of the umbilical vessels grow into the mesoderm; in this way, the chorionic villi are vascularized.
  • At this point, the villi contain trophoblast, mesoderm, and blood vessels.

• 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.

• Muscle Development

  • Myogenesis is the formation of muscle tissue during embryonic development from stem cells in the mesoderm.
  • The first differentiation of the hESCs that form the embryo proper, is in three cell types known as the germ layers: the ectoderm, the mesoderm, and the endoderm.
  • The mesoderm forms the skeleton and muscles, heart and circulatory system, urinary and reproductive systems, and connective tissues inside the body.