Stomodes

A stomode, also known as a stomodaeum or stomodeum, is an embryonic invagination that forms the primitive mouth in chordates and some invertebrates. It represents the point where the ectoderm and endoderm meet before the formation of the oral membrane.

During early development, the stomode develops as a depression in the surface ectoderm. It grows inward to meet the foregut (derived from endoderm), thereby creating a thin epithelial membrane called the oral membrane or buccopharyngeal membrane. This membrane then ruptures, establishing a connection between the mouth cavity and the digestive tract.

The stomode's development is crucial for the proper formation of the mouth and the subsequent development of associated structures like the jaws, teeth, and salivary glands. Malformations in the development of the stomode can lead to various congenital conditions affecting the face and oral cavity.