VAN 211: Veterinary Histology and Embryology (2+2)

MOUTH

• The first indication of the embryonic mouth is the stomodeum - an indentation of the ventral surface of the embryo at the level of first branchial arch.
• The stomodeum enlarges and becomes deeper. A defnite stomodeal cavity is formed at two weeks of gestation in most of the embryos. Shortly thereafter,the oropharyngeal memberane ruptures which allow the communication between the stomodeum and the floor of the pharynx.
• The rupture of the memberane allows structures arising from the pharynx to extend into the adjacent part of the stomodeum.
• After the rupture of the oral memberane,it is impossible to determine the exact junction of the ectoderm and endoderm in the mouth cavity.
• The terminal sulcus on the root of the tongue marked by the presence of circumvallate papillae is the only demarcation.
• The stomodeal part is lined with the ectodermal epithelium and the pharyngeal part with endodermal epithelium.