Head

Head is the uppermost part of the human body. It is a complex region which can be broadly divided into the face and the scalp. The face is the anterior aspect of the head, while the scalp covers the superior, lateral and posterior head regions.

The head comprises of several compartments, including the cranial cavity, the ears, two orbits, two nasal cavities and an oral cavity.

The cranial cavity of the head is a bony capsule which hosts the brain, its meninges and vasculature. Both middle and inner ears, as well as major part of the external ear canal, reside within the bones forming the floor of the cranial cavity. The auricle or pinna of the external ear protrudes out from the sides of the cranial cavity.

The orbital cavities are cone-shaped bony chambers. Their bases face forwards onto the face, while the apices are directed posteromedially. They are situated immediately below the frontal aspect of the floor of the cranial cavity. The orbits contain the eyeballs and surrounding structures, including the extra-ocular muscles.

The nasal cavities are sandwiched between the two orbital cavities and rest immediately above the oral cavity. Their walls are bony and cartilaginous and open anteriorly onto the face via the anterior nasal apertures (or nostrils), while communicate posteriorly with the nasopharynx via the posterior nasal apertures (or choanae). The nasal cavities extend laterally as four pairs of paranasal sinuses, into the bones of the cranial cavity and the facial skeleton.

The oral cavity lies immediately underneath the nasal cavities, from which it is separated via the hard and soft palate. Anteriorly, the oral cavity opens to the exterior as the mouth, while posteriorly it communicates with the oropharynx via the oropharyngeal isthmus.

Two additional well-confined compartments in the head region include the infratemporal and the pterygopalatine fossae. The former hides inner to the ramus of the mandible while the latter hides deep, immediately posterior to the upper jaw bone (the maxilla) underneath the cranial cavity.