Anatomy chapters
Facial injuries and cleft lip and palate
How the face and palate develop and why clefts form, plus the common facial fractures (nasal, zygomatic, Le Fort, mandible) and the nerves they damage.
- The face forms from five prominences around the mouth; cleft lip is failure of the maxillary and medial nasal prominences to fuse.
- Cleft palate is failure of the palatine shelves to fuse with each other or with the primary palate.
- Facial fractures matter because of nerves: infraorbital with zygomatic and orbital floor fractures, inferior alveolar with mandibular fractures.
On this page
Overview
The face develops in weeks 4 to 10 from swellings around the primitive mouth. Clefts form when these swellings fail to fuse.
Facial injuries are common after road accidents, falls and assaults. Their anatomy matters because of the nerves, the eye and the airway nearby.
Development of the face
Five facial prominences surround the stomodeum (primitive mouth) in week 4:
- One frontonasal prominence above.
- Two maxillary prominences at the sides (from the first pharyngeal arch).
- Two mandibular prominences below (from the first pharyngeal arch).
Nasal placodes appear on the frontonasal prominence and sink into nasal pits. The ridges around each pit form the medial and lateral nasal prominences.
| Prominence | Forms |
|---|---|
| Frontonasal | Forehead, bridge of the nose |
| Medial nasal (fused as the intermaxillary segment) | Middle of the nose, philtrum of the upper lip, the four upper incisors and the primary palate |
| Lateral nasal | Sides (alae) of the nose |
| Maxillary | Cheeks, lateral upper lip, maxilla and the secondary palate |
| Mandibular | Lower lip, chin and lower jaw |
The upper lip forms from the medial nasal prominences (middle) and the maxillary prominences (sides).
Development of the palate
- Primary palate: a small triangle in front, from the intermaxillary segment.
- Secondary palate: formed by two palatine shelves that grow from the maxillary prominences. They start vertical beside the tongue, then lift to horizontal as the tongue drops, and fuse in the midline in weeks 7 to 10.
The incisive foramen marks the border between the primary and secondary palate.
The primary palate lies in front of the incisive foramen; the secondary palate lies behind it.
Clefts
Cleft lip
How it happens: the maxillary prominence fails to fuse with the medial nasal prominence on one or both sides.
What you see: a gap in the upper lip to one side of the philtrum (not in the midline). It may extend into the nose and the alveolus and join a cleft palate.
Cleft palate
How it happens: the palatine shelves fail to fuse with each other, with the nasal septum or with the primary palate.
What you see: a gap in the roof of the mouth. Babies have trouble feeding (milk comes through the nose), and later have nasal speech and middle ear problems because the muscles that open the auditory tube are affected.
Clefts are grouped by their relation to the incisive foramen:
| Group | Involves |
|---|---|
| Anterior clefts | Lip and/or primary palate (in front of the incisive foramen) |
| Posterior clefts | Secondary palate (behind the incisive foramen) |
| Combined | Both |
Cleft lip (with or without cleft palate) is commoner in males. Isolated cleft palate is commoner in females, because the shelves fuse about a week later in girls.
Risk factors include family history, smoking, valproate and phenytoin in pregnancy, and some genetic syndromes. Folic acid may lower the risk.
A median cleft lip (in the midline) is rare and comes from incomplete merging of the two medial nasal prominences, not the usual cause.
Facial injuries
Nasal fractures
The commonest facial fracture. Look for a septal haematoma, a swelling of the nasal septum that must be drained quickly or the cartilage can die and the nose collapse (saddle nose).
Zygomatic (cheek) fractures
How it happens: a direct blow to the cheek.
What you see: a flattened cheek, a step in the lower orbital rim, numbness of the cheek, side of the nose and upper lip (infraorbital nerve), and sometimes difficulty opening the mouth if the arch presses on the coronoid process.
Orbital blow-out fracture
How it happens: a blunt object such as a fist or ball hits the eye. Pressure inside the orbit breaks the thin orbital floor into the maxillary sinus.
What you see: double vision on looking up because the inferior rectus is trapped, a sunken eye, and a numb cheek from infraorbital nerve injury.
Orbital floor fracture = infraorbital nerve numbness + trapped inferior rectus.
Le Fort fractures of the maxilla
| Type | Line of fracture | Result |
|---|---|---|
| Le Fort I | Horizontal, just above the teeth and through the maxillary sinuses | The tooth-bearing part of the maxilla moves |
| Le Fort II | Pyramid shape, through the nasal bones and the floor of the orbits | The middle of the face moves |
| Le Fort III | Through the orbits and zygomatic arches | The whole face is separated from the skull (craniofacial separation) |
Le Fort II and III fractures can tear the dura and cause CSF leaking from the nose, and can block the airway.
Mandibular fractures
How it happens: a blow to the jaw. The mandible often breaks in two places, for example the body on one side and the neck of the condyle on the other.
What you see: a change in the bite, pain and, if the fracture runs through the canal, numbness of the lower lip and chin (inferior alveolar and mental nerve).
The neck of the mandible and the region of the canine tooth (long root) are weak points.
Scalp wounds
The scalp bleeds a lot because its arteries are held open by the dense connective tissue. A wound that cuts the epicranial aponeurosis gapes wide.
Typical questions: which prominences fail to fuse in cleft lip, the role of the incisive foramen, sex differences in clefts, the nerve damaged in zygomatic and orbital floor fractures, the muscle trapped in a blow-out fracture, and the planes of Le Fort fractures.
Quick revision
- Face: frontonasal, two maxillary, two mandibular prominences.
- Philtrum and primary palate: medial nasal prominences.
- Cleft lip: maxillary fails to fuse with medial nasal prominence; lateral to the midline.
- Cleft palate: palatine shelves fail to fuse; incisive foramen separates primary and secondary palate.
- Cleft lip commoner in boys; isolated cleft palate in girls.
- Orbital floor fracture: infraorbital nerve and inferior rectus.
- Le Fort I horizontal; II pyramidal; III craniofacial separation.
Written by The House Job from standard anatomy and embryology references (Snell's Clinical Anatomy by Regions; Langman's Medical Embryology).
FAQ
What causes cleft lip?
Failure of the maxillary prominence to fuse with the medial nasal prominence.
What separates the primary and secondary palate?
The incisive foramen.
Which nerve is injured in a fracture of the orbital floor?
The infraorbital nerve, causing numbness of the cheek and upper lip.
What is a Le Fort III fracture?
A fracture through the orbits and zygomatic arches that separates the face from the skull.