Skull
The skull has 22 bones, excluding the ossicles of the ear. Except for the mandible, which forms the lower jaw, the bones of the skull are attached to each other by sutures, are immobile, and form the cranium.
The cranium can be subdivided into:
The cranium can be subdivided into:
- an upper domed part (the calvaria), which covers the cranial cavity containing the brain;
- a base that consists of the floor of the cranial cavity; and
- a lower anterior part-the facial skeleton (viscerocranium).
The bones forming the calvaria are mainly the paired temporal and parietal bones, and parts of the unpaired frontal, sphenoid, and occipital bones.
The bones forming the base of the cranium are mainly parts of the sphenoid, temporal, and occipital bones.
The bones forming the facial skeleton are the paired nasal bones, palatine bones, lacrimal bones, zygomatic bones, maxillae, inferior nasal conchae, and the unpaired vomer.
The mandible is not part of the cranium nor part of the facial skeleton.
Anterior view
The anterior view of the skull includes the forehead superiorly, and, inferiorly, the orbits, the nasal region, the part of the face between the orbit and the upper jaw, the upper jaw, and the lower jaw.
Frontal bone
The forehead consists of the frontal bone, which also forms the superior part of the rim of each orbit.
Just superior to the rim of the orbit on each side are the raised superciliary arches. These are more pronounced in men than in women. Between these arches is a small depression (the glabella).
The bones forming the base of the cranium are mainly parts of the sphenoid, temporal, and occipital bones.
The bones forming the facial skeleton are the paired nasal bones, palatine bones, lacrimal bones, zygomatic bones, maxillae, inferior nasal conchae, and the unpaired vomer.
The mandible is not part of the cranium nor part of the facial skeleton.
Anterior view
The anterior view of the skull includes the forehead superiorly, and, inferiorly, the orbits, the nasal region, the part of the face between the orbit and the upper jaw, the upper jaw, and the lower jaw.
Frontal bone
The forehead consists of the frontal bone, which also forms the superior part of the rim of each orbit.
Just superior to the rim of the orbit on each side are the raised superciliary arches. These are more pronounced in men than in women. Between these arches is a small depression (the glabella).
- Medially, the frontal bone projects inferiorly forming a part of the medial rim of the orbit.
- Laterally, the zygomatic process of the frontal bone projects inferiorly forming the upper lateral rim of the orbit. This process articulates with the frontal process of the zygomatic bone.
Zygomatic and nasal bones
The lower lateral rim of the orbit, as well as the lateral part of the inferior rim of the orbit is formed by the zygomatic bone (the cheekbone).
Superiorly, in the nasal region the paired nasal bones articulate with each other in the midline, and with the frontal bone superiorly. The center of the frontonasal suture formed by the articulation of the nasal bones and the frontal bone is the nasion.
Laterally, each nasal bone articulates with the frontal process of each maxilla.
Inferiorly, the piriform aperture is the large opening in the nasal region and the anterior opening of the nasal cavity. It is bounded superiorly by the nasal bones and laterally and inferiorly by each maxilla.
Visible through the piriform aperture are the fused nasal crests, forming the lower part of the bony nasal septum and ending anteriorly as the anterior nasal spine, and the paired inferior nasal conchae.
Maxillae
The part of the face between the orbit and the upper teeth and each upper jaw is formed by the paired maxillae.
- Superiorly, each maxilla contributes to the inferior and medial rims of the orbit.
- Laterally, the zygomatic process of each maxilla articulates with the zygomatic bone and medially, the frontal process of each maxilla articulates with the frontal bone.
- Inferiorly, the part of each maxilla, lateral to the opening of the nasal cavity, is the body of maxilla.
On the anterior surface of the body of maxilla, just below the inferior rim of the orbit, is the infra-orbital foramen.
Inferiorly, each maxilla ends as the alveolar process, which contains the teeth and forms the upper jaw.
Mandible
The lower jaw (mandible) is the most inferior structure in the anterior view of the skull. It consists of the body of mandible anteriorly and the ramus of mandible posteriorly. These meet posteriorly at the angle of mandible. All these parts of the mandible are visible, to some extent, in the anterior view.
The body of mandible is arbitrarily divided into two parts:
- the lower part is the base of mandible;
- the upper part is the alveolar part of mandible.
Laterally, a mental foramen is visible halfway between the upper border of the alveolar part of mandible and the lower border of the base of mandible. Continuing past this foramen is a ridge (the oblique line) passing from the front of the ramus onto the body of mandible. The oblique line is a point of attachment for muscles that depress the lower lip.
Sources :
- Gray's Anatomy for Students, 2nd Edition ( 812 – 813 – 814 ) .
- Gray's Anatomy for Students, 2nd Edition ( 812 – 813 – 814 ) .
Copyright © 2009 by Churchill Livingstone
