Skull • Usually consists of 22 bones, all of which (except the lower jaw) are firmly interlocked along lines called “sutures”. • Cranium = 8 bones • Facial skeleton = 13 bones + lower jaw • Lower jaw bone is called the mandible, and is the only movable bone.
Cranium • Functions: • Encloses and protects the brain • Provides attachments for muscles that make chewing and head movement possible • Has air-filled, mucous-membrane-lined (??), sinus cavities
Cranial Bones • Frontal bone • Parietal bones (2) • Occipital bone • Temporal bones (2) • Sphenoid bone • Ethmoid bone
Cranial Bones, continued….. • Frontal bone • Anterior portion of skull above the eyes • Houses 2 frontal sinuses, one above each eye near the midline • Parietal bones • One on each side of the skull just behind the frontal bone • Form bulging sides and roof of cranium • Fused at midline (sagittal suture) and to frontal bone (coronal suture)
Cranial Bones, continued….. • Occipital bone • Joins the parietal bones (lambdoidal suture) • Forms back of skull and base of cranium • Foramen magnum – opening at bottom of occipital bone for nerve processes to connect to spinal cord • Occipital condyles – rounded processes on each side of foramen magnum that articulate with 1st vertebra
Cranial Bones, continued….. • Temporal bones • On each side of the skull • Joins parietal bone (squamosal suture) • Form parts of sides and base of cranium • External auditory meatus(???) • Mandibularfossae– depressions in the temporal bone that articulate with condyles(???) of the mandible
Cranial Bones, continued….. • Temporal bones, continued…. • Below each external auditory meatus: • Mastoid process – rounded attachment for certain neck muscles • Styloid process – long, pointed anchor for muscles associated with tongue and pharynx • Zygomatic process • Projects anteriorly(???) from temporal bone, joins the zygomatic bone (“cheek bone”), and helps form prominence of the cheek
Cranial Bones, continued….. • Sphenoid bone • Wedged between several other bones in anterior portion of cranium • Has a central portion and 2 wing-like structures that extend laterally (???) • Helps form base of cranium, sides of skull, and sides of orbits (“eye sockets”) • Midline of sphenoid bone has a depression (sellaturcica) that houses pituitary gland • Contains 2 sphenoidal sinuses
Cranial Bones, continued….. • Ethmoid bone • Located in front of sphenoid bone • Consists of 2 masses, one on each side of nasal cavity • Masses joined by thin cribriform plates (???) • Cribriform plates form part of nasal cavity roof. • Cristagalli – triangular process between cribriform plates • Perpendicular plate • projects downward from cribriform plates • helps form nasal septum
Cranial Bones, continued….. • Ethmoid bone, continued….. • Superior nasal concha and middle nasal concha - project inward from lateral portions of ethmoid bone toward perpendicular plate • Lateral portions of ethmoid bone contain small air spaces (ethmoidal sinuses)
Facial Skeleton • Maxillae (2) • Form the upper jaw • Portions comprise the anterior (???) roof of the mouth (“hard palate”), the floors of the orbits (???), and the sides and floor of the nasal cavity. • Contain sockets of the upper teeth • “Maxillary sinuses” • Inside the maxillae, lateral (???) to nasal cavity • The largest of the sinuses
Facial Bones, continued…. • Maxillae, continued…. • “Palatine processes” fuse midline (???) to form anterior section of hard palate • Teeth are found in cavities in the “alveolar arch” (aka “dental arch”) formed by the “alveolar processes” projecting downward from the inferior (???) border of the maxillae.
Facial Bones, continued…. • Palatine bones • Behind the maxillae • Horizontal portions form posterior (???) section of hard palate and floor of nasal cavity • Perpendicular portions help form lateral (???) walls of nasal cavity
Facial Bones, continued….. • Zygomatic bones (“???”) • Also help form lateral walls and floors of the orbits • Each bone has a “temporal process” that connects to the zygomatic process (forming the zygomatic arch). • Lacrimal bones • Thin, scale-like structure in medial wall (??) of each orbit between ethmoid bone and maxilla
Facial Bones, continued….. • Nasal bones • Long, thin, and nearly rectangular • Lie side by side and fused at midline to form bridge of nose • Vomer bone • Thin and flat • Along midline in nasal cavity • Joins perpendicular plate of ethmoid bone posteriorly (???) to form nasal septum
Facial Bones, continued….. • Inferior nasal conchae • Fragile, scroll-shaped bones attached to lateral walls (???) of nasal cavity • Support mucous membranes in nasal cavity • Mandible (“???”) • Upward projection at ends: • Posterior “mandibular condyle” articulates with mandibular fossae on _______ bone • Anterior “coronoid process” provides attachments for muscles for chewing • “Alveolar arch” – curved, superior (???) border that contains sockets for lower teeth