Viscerocranium

Viscerocranium or splanchnocranium refers to the portion of the skull that consists of the facial bones. The viscerocranium is derived from the embryonic pharyngeal arches, and its components serve primarily in the formation of the face, including the cavities of the nose, mouth, and pharynx.

Development

The viscerocranium develops from the neural crest cells of the embryo, which migrate to form the pharyngeal arches. Each arch gives rise to specific structures in the mature skull. For example, the first pharyngeal arch forms the mandible (lower jaw) and the maxilla (upper jaw).

Components

The viscerocranium includes several bones, which can be divided into those of the upper and lower face.

Upper Face

• The nasal bone forms the bridge of the nose.
• The lacrimal bone is a small bone located in the eye socket.
• The zygomatic bone forms the cheekbone.
• The maxilla forms the upper jaw and the roof of the mouth.

Lower Face

• The mandible forms the lower jaw.
• The vomer is a thin bone that forms part of the nasal septum.
• The palatine bone forms the back of the nasal cavity and a small part of the hard palate.

Function

The viscerocranium serves several functions. It forms the framework of the face and provides attachment points for the muscles of facial expression and mastication. It also forms part of the respiratory tract and digestive tract, housing the cavities of the nose, mouth, and pharynx.

Clinical Significance

Abnormalities in the development of the viscerocranium can lead to conditions such as cleft palate and Pierre Robin sequence, which involve malformations of the facial bones.

See Also

• Neurocranium
• Skull
• Pharyngeal arches