Frog organogenesis

The frog organogenesis will be studied as an example of the general organogenesis of vertebrates.

The following scheme explains in a simplified way how the initial phase of organogenesis occurs in these animals: neurulation.

Some of the final destinations of embryonic leaflets in vertebrates in general are:

Ectoderma Mesoderm Endoderm
  • Epidermis and dermal derivatives, with mucous glands;
  • all structures of the nervous system;
  • Epithelium lining the nasal, anal and oral cavities.
  • Dermis;
  • Muscles;
  • Cartilage, bones and other connective tissues;
  • Blood, bone marrow and lymphatic tissues;
  • Organs of the genital and urinary system.
  • Digestive tract lining epithelium (except oral and anal cavities);
  • Liver and pancreas;
  • Respiratory system (except nasal cavities)

Special embryonic cells typical and unique to vertebrates form the neural crest. These cells differentiate along with the formation of the neural tube from the embryo ectoderm. They are arranged next to the neural tube, but posterior to the brain region.

Neural crest cells have the ability to migrate throughout the body, giving rise to various cell types, such as sensory neurons from the peripheral nervous system, adrenal medulla cells, dermis of the head skin, and pigmentary skin cells throughout the body.

It is considered today that the definitive step in the origin of vertebrates was the evolution of neural crest cells. No other animal has them.