Oral Cavity Development

• Development of the oral cavity with Dr. Buvana Balamugundan.

Primitive Oral Cavity (3-4 Weeks)

• The stomodeum is a narrow slit-like opening in the face.
• It forms primarily through the longitudinal folding of the early embryo.
• The stomodeum is lined by ectoderm.
• The stomodeum lies between the brain capsule (above) and the pericardial sac (below) during development.
• A thin oral membrane at the back of the cavity separates the primitive mouth from the pharynx, which disappears later.

Facial Structures Derived from Stomodeum

• Face derives from structures around the stomodeum.
• The frontonasal process is single and ventral to the forebrain.
• Maxillary processes are paired and develop from the cranial part of the first branchial arch.
• Mandibular processes are paired and develop from the caudal part of the first branchial arch.

Derivatives of Facial Components

• Frontonasal process forms the forehead, external nose, nasal cavity, and nasal septum.
• Maxillary process forms the lateral parts of the upper lip and upper parts of the cheek.
• Mandibular process forms the chin, lower lip, and lower part of the cheek.

Intermaxillary Segment

• Two medial nasal processes fuse to form the intermaxillary segment.
• If this fusion fails, an orofacial cleft may develop in newborns.
• The intermaxillary segment consists of 3 components: labial (philtrum of the upper lip), upper jaw (alveolar process carrying 4 incisor teeth), and palatal (triangular primary palate or premaxilla).

Nasal Processes

• Naso-medial processes grow quickly, pushing the frontal prominence.
• They fuse with the maxillary processes to complete the arch of the upper jaw.
• Maxillary processes grow medially, press medial nasal processes, and fuse with them.
• Maxillary processes also fuse with lateral nasal and mandibular processes.
• Mandibular prominences fuse and form the chin, lower lip, and lower cheek regions (mandible).

Palatogenesis

• Palatogenesis begins at the end of the 5th week and completes by the end of the 12th week.
• The palate develops from two primordia: the primary and secondary palates.

Primary Palate

• The primary palate begins to develop early in the 6th week.
• It originates from the deep part of the intermaxillary segment, as the median palatine process.
• It fuses with the developing secondary palate.
• The primary palate represents a small part anterior to the incisive fossa of the adult hard palate.

Secondary Palate

• The secondary palate develops from the internal aspect of the maxillary processes, as the lateral palatine process, beginning in the 6th week.
• Lateral palatine processes elongate and ascend to a horizontal position above the tongue.
• Bone develops in the anterior part, forming the hard palate.
• The posterior part develops as muscular soft palate.
• Lateral palatine processes grow medially and fuse in the median plane.
• It also fuses with the primary palate and the nasal septum.

Development of Secondary Palate

• The main palate is formed by palatine shelves growing inwards into the upper pharynx.
• Palatine shelves grow toward each other and above the tongue.
• The nasal septum grows downwards towards the palatine shelves.

Palatine Bone

• The palatine bone is a paired bone located between the maxilla and the pterygoid process of the sphenoid bone.
• It participates in building the oral and nasal cavities, and the orbits within the skull.
• The quadrilateral horizontal plate posterior to the maxilla has a nasal (superior) and a palatine (inferior/oral) surface.
• The anterior border is serrated and attaches to the palatine process of the maxilla at the palatomaxillary (transpalatine) suture.

Permanent Palate

• The primary palate results from the fusion of medial nasal processes.
• The secondary palate results from the fusion of shelf-like outgrowths, the palatine shelves from the inner aspect of maxillary processes.
• The secondary and primary palates fuse anteriorly in a 'Y' shape.
• Each limb passes between the lateral incisor and canine teeth.
• The junction between the primary and secondary palate is represented by the incisive fossa in adults.

Anomalies Related to Palate

• Cleft palate is a birth defect with an opening in the oral cavity due to a lack of tissue development.
• Cleft palate is associated with craniofacial and genetic sequences or syndromes.
• Examples of syndromes: Pierre Robin sequence, Treacher-Collins syndrome, and Craniofacial microsomia.