Face & Palate Development and Clefts

Facial prominences and what they form

Prominence	Forms
Frontonasal	Forehead, bridge and tip of the nose (via the medial and lateral nasal processes)
Medial nasal processes (fused)	Intermaxillary segment: philtrum of the upper lip, premaxilla with the four incisors, primary palate
Lateral nasal processes	Alae of the nose
Maxillary processes	Cheeks, lateral upper lip, most of the maxilla, secondary palate (palatal shelves)
Mandibular processes	Lower lip, chin, mandible (the first to fuse in the midline)

Face formation occurs mostly in weeks 4–8; the processes surround the stomodeum (primitive mouth).

Primary palate: from the intermaxillary segment, anterior to the incisive foramen.
Secondary palate: palatal shelves grow from the maxillary processes, first vertically beside the tongue, then elevate horizontally as the tongue drops and the mandible grows; they fuse with each other, the primary palate and the nasal septum.
Fusion proceeds from anterior to posterior, starting around week 7–8 and finishing around week 12 (ranges differ by textbook).
The incisive foramen marks the junction of the primary and secondary palates and is the reference point for classifying clefts.

Cleft	Failure of	Notes
Cleft lip	Fusion of the medial nasal process with the maxillary process	Unilateral more often than bilateral; left side more often; more common in males
Cleft of the primary palate	Same fusion, extending to the incisive foramen	Often with cleft lip; may involve the lateral incisor region (missing or extra laterals)
Cleft of the secondary palate	Palatal shelves to fuse with each other	Isolated cleft palate is more common in females; ranges from bifid uvula to complete cleft
Oblique facial cleft	Maxillary process with the lateral nasal process	Exposes the nasolacrimal duct; rare

Pierre Robin sequence: small mandible → tongue stays high → palatal shelves cannot elevate → U-shaped cleft palate and airway obstruction.
Risk factors include genetics, smoking, alcohol, anticonvulsants (phenytoin), retinoids and low folate; folic acid supplementation lowers neural-tube and some cleft risk.

Attributing cleft lip to failed fusion of the two medial nasal processes: classic cleft lip is medial nasal + maxillary process (a true midline cleft lip is rare).
Saying isolated cleft palate is more common in males: CL±P favors males, isolated CP favors females.
Forgetting that the premaxilla carries all four maxillary incisors, which is why clefts often affect the lateral incisor.
Placing the start of palatal fusion in the posterior: fusion proceeds anterior to posterior.

Pick an answer to see right away whether it is correct and why.

0 of 5 answered

Answer key: 1 C · 2 A · 3 C · 4 B · 5 B