Infant Palate Development

The development of the face and palate is centered around five structures known as prominences. They begin growing between the fourth and tenth week of pregnancy, eventually fusing together to form the bones of the face. The top portion is known as the frontonasal prominence. On each side there is a maxillary prominence and a manibular prominence, for a total of four.

Formation of Pharyngeal Arch I

• In the fourth week of pregnancy, on the surface of the head and neck, five ridges form. These are known as pharyngeal or branchial arches. Covered by ectoderm, the spaces between are known as clefts and are filled with ectoderm. The arches have a cartilage-like core, a cranial nerve and an aortic arch. The pharyngeal arches term indicates their location near the pharynx.

Maxillary and Mandibular Prominences

• From Pharyngeal Arch I, the mandibular and maxillary prominences form around a structure known as the stomodeum, or primordial mouth. Less than a millimeter in size, the maxillary prominence, shaped like a vertical oval that is more narrow on the upper end, forms above the mandibular prominence, shaped like a horizontal oval with a very slight hook upward in the center, where it meets the prominence on the opposite side.

Frontonasal Prominence

• Near the brain, from the mensenchyme, frontonasal prominence forms. Also less than a millimeter in size, it is shaped like an upside down heart, with the top end being curved instead of coming to a point.

Nasal Placodes

• Remembering the upside down heart-like shape, during week five, the frontonasal prominence develops two thickenings on each lower side. This is the beginning of the development of the nose structure, called a nasal placode. In week six, a small depression develops on each nasal placode, and these will later become the nostrils. From this point, two more prominences form from each nasal placode, the lateral nasal processes on the outer side and the medial nasal processes facing inward. A small groove separates the nasal processes from the maxillary prominence, this is known as the nasolacrimal groove. If this groove does not close, and the lateral nasal prominence does not fuse to the maxillary prominence, it is a condition known as an oblique facial cleft.

Coming Together

• If one observed each of the five prominences coming together, they would see the maxillary and mandibular prominence on each side of the head, and the frontonasal prominence on top. Each side, containing the maxillary and mandibular prominences, would slowly move toward the center of what will become the face, with the frontonasal prominence moving downward.