Embryonic Development

Organogenesis Overview

• Endoderm derives structures including the gastrointestinal tract, liver, pancreas, and respiratory system.
• The primitive streak marks the beginning of gastrulation, establishing the body's axial structure and facilitating cellular migration for organ formation.

Germ Layers and Their Roles

• The placenta is primarily formed from the trophoblast layer, which is derived from the outer cell mass of the blastocyst.
• Neural tube formation occurs through a process called neurulation, where the neural plate folds and fuses to create the tube that becomes the central nervous system.
• The mesoderm gives rise to structures including muscles, bones, and the circulatory system.

Key Processes in Organogenesis

• Embryonic folding occurs laterally and in the cephalocaudal direction, allowing the embryo to assume a more cylindrical shape necessary for development.
• The sacrococcygeal region is associated with body cavities and blood islands, crucial for early blood cell formation and circulation.

Ectoderm Contributions

• The ectoderm is responsible for forming the epidermis, nervous system, and sensory organs during organogenesis.
• Structures NOT derived from the mesoderm include the epidermis and neural tissues, which originate from the ectoderm.

Essential Germ Layers

• The liver develops from the endoderm as part of the foregut during organogenesis, highlighting its critical role in digestive system formation.