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

LIPS AND GUMS

• The maxillary and mandibular prominences that form the jaws are originally solid masses of mesenchyme covered with the ectoderm.
• At about 3 ½ weeks, in the ectodermal epithelial lining of the mouth, a horse-shoe shaped thickened band of cells appear on each jaw.
• The band of epithelial cells begins to grow into the underlying mesenchyme thereby causing bands to become the grooves.
• Along the course of the original band, the epithelial lamina is formed because of the sufficient penetration of epithelium into the mesenchyme.
• Then the lamina splits forming a peripheral layer of tissue to form the lips (labia oris) and a medial layer of tissue to form the gums (gingiva). Thus, the grooves and the lamina are called labio-gingival groove and lateral lamina respectively.
• The space created by the labio-gingival lamina is called the vestibule.