The Skull

Seatwork: Which bone is known as the Keystone of the facial skeleton?

The Maxillae aka Maxillary Bones All facial bones except the mandible articulate with the maxillae

The Skull The skull is made up of 22 bones; Including: 8 cranial bones 13 facial bones The mandible

Infant Skull Incompletely developed Separated by fibrous membranes called FONTANELS (aka soft spots)

Cranium: (aka Braincase) Houses brain Encloses & protects the brain, provides attachments for muscles, and contains air-filled sinuses that reduce its weight Features of the frontal bone (behind forehead): Supraorbital foramina (notch) above the orbital cavity; where blood vessels & nerves pass to forehead tissues 2 frontal sinuses

Cranium cont’d Parietal bones—lie at sides of cranium posterior to the frontal bone. Join at sagittal suture. They meet the frontal bone along the coronal suture. Occipital bone—lie at back & base of cranium. Lambdoidal suture (between the parietal & occipital) Foramen magnum (where spinal cord passes through) Occipital condyles (articulate with the 1st vertebra) Condyles: rounded processes that usually articulate with another bone

Cranium cont’d Temporal bones—at sides of cranium (lower area where ear openings are found) Squamosal suture (between temporal & parietal bone) External auditory/acoustic meatus (ear canal in temporal bone) Mandibular fossae (articulate with mandible) Mastoid process (attaches to neck muscles; a spongy bone that projects from the temporal) Styloid process (anchors muscles, tongue & pharynx) Zygomatic process (projects anteriorly and joins with the temporal process of the zygomatic bone to help form the cheek) Fossa—deep pit/depression

Cranium cont’d Sphenoid bone—winged bone at anterior floor of cranium Sella turcica —saddle shaped depression that houses pituitary gland Sphenoid sinuses

Cranium cont’d Ethmoid bone—in front of sphenoid Cribiform plates (hold it together) Perpendicular plate (goes downward into nasal cavity & forms nasal septum) Superior & middle nasal conchae —coils/folds of bone that project inward into nasal cavity Ethmoidal sinuses Crista galli —projects into cranial cavity; upward attachment for membranes around the brain Note: the inferior nasal conchae—considered part of facial skeleton; they increase surface area in the nasal cavity

Figure 7.7 The Ethmoid bone (anterior view)

FACIAL SKELETON The 13 immovable facial bones & the moveable mandible bone of the lower jaw form the face; they provide attachments for muscles of mastication & expression (total number of facial bones = 14)

Facial Skeleton cont’d The maxillae (maxillary bones) form: The upper jaw Hard palate Formed anteriorly by the fusing of the palatine processes & posteriorly by the palatine bones) Floor of the orbits Sides of the nasal cavity House the upper teeth Alveolar process –inferior part of each maxillary bone projects downward, holds upper teeth) Maxillary sinuses (largest sinuses in skull)

Facial Skeleton Cont’d Palatine bones: L-shaped bones located behind maxillae; form the floor of the nasal cavity & posterior part of hard palate Zygomatic bones: make up cheekbones; join with the temporal bones to form the zygomatic arches Lacrimal bones: form part of the medial walls of the orbits Nasal bones: form bridge of nose

Facial Skeleton Cont’d Vomer bone: makes up lower part of nasal septum Inferior nasal conchae: fragile scroll shaped bones that support mucous membranes within the nasal cavity Mandible (aka lower jawbone): supports lower teeth Includes mandibular condyle Coronoid process (anterior projection of mandible) Alveolar arch

Bones forming left lateral wall of nasal cavity (nasal septum removed)

The end