The external features of the face develop from five primordia. The upper part of the face, including the forehead, nose, orbit and lacrimal apparatus and nasal cavity forms from the unpaired frontonasal prominence.
The upper jaw and palate develop from the paired maxillary prominences of the first branchial arch and the lower jaw from the paired mandibular prominences of the first branchial arch.
Five primordia contribute to the external features of the face. The frontonasal prominence forms midline structures. The two maxillary processes contribute to the upper jaw and palate and the two mandibular processes fuse to form the mandible.
Note that the nasal pits, which will perforate to form the nostrils, are surrounded by the medial and lateral nasal swellings.
The nasolacrimal groove is located between the lateral nasal swelling and the maxillary process and will contribute to the formation of the nasolacrimal duct. Note its relationship to the eye.
The medial nasal swellings (folds) are pushed toward the midline by the medial growth of the maxillary processes. Eventually, they will fuse in the midline to form a midline portion of the lip and upper jaw known as the intermaxillary segment because it is located between the parts of the lip and upper jaw that is formed by the maxillary processes.
The medial and lateral nasal swellings (folds) surround the external nares, openings into
the nasal cavity.
The medial nasal swellings (folds) are pushed together in the midline by the advancing maxillary processes. They form a midline portion of the upper jaw and face, called the intermaxillary segment of the face.
This segment has several components:
By the 8th week of development, the face has a distinctively human appearance. Note that the fused medial nasal swellings, in addition to contributing to the midline of the upper lip, jaw and palate also contribute to the nose. Observe that the auricles of the ear are developing in the cervical region, but will eventually ascend to their final position, parallel to the eyes.
The nose is a prominent feature of the human face. It is composed mainly of cartilage derived from five primordia. The bridge of the nose is bony and is formed by the frontonasal prominence itself. The crest and the tip of the nose are formed by the fused medial nasal swellings and are largely cartilage. The sides of the nose and alae are largely cartilaginous and formed from the lateral nasal swellings.
The palate consists of the anterior hard palate & posterior soft palate. Developmentally it forms from two sources:
Primary Palate
Around 6.5 weeks, the medial nasal swellings are fused with each other but not yet with the maxillary processes. In this superior view of the palate, we can see up into nasal cavity to observe the nasal septum growing downward toward the palatine processes. The palatine processes are growing toward each other in the midline. The green line marks the relative location of the coronal cut below.
In the coronal section to the right, note that the palatine processes are directed downward and that the tongue protrudes into the nasal cavity.
The primary palate is fusing with secondary palate. The palatine processes of the maxillary processes continue to grow toward midline where they will eventually fuse with each other and the nasal septum.
The nasal septum continues its downward growth toward the palate.
In the coronal section below, the palatine processes can be see to have returned to a more horizontal position and the tongue is now confined to the oral cavity.
Around 10 weeks of development, the primary and secondary palates have fused and the secondary palate is completed by fusion of the palatine processes of the maxillary processes.
In the coronal section below, we see that the nasal septum has also fused with the completed palate, dividing the nasal cavity into right and left sides.
Anterior cleft deformities may involve the lip, upper jaw and/or primary palate. These are located anterior to the incisive foramen, the boundary between the primary and secondary palates. They may be located unilaterally as in the image above on the left, or bilateral as in the image above on the right. They may also coexist with cleft of the secondary palate.
Posterior cleft deformities are located behind the incisive foramen and involve failure of fusion of the palatine processes of the maxillary processes. They may be unilateral or bilateral and can occur in conjunction with cleft lip and primary palate as seen in the images below.