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 Cavities open to outside

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) Start labeling skull diagrams from Lab Exercise 13 in Hole’s Lab Manual

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 (???) Mandibular fossae – depressions in the temporal bone that articulate with condyles (???) of the mandible What does “meatus” mean? (passage) What could the external auditory meatus be?

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 (sella turcica) 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. Crista galli – triangular process between cribriform plates Perpendicular plate projects downward from cribriform plates helps form nasal septum Cribr = sieve (These plates have tiny openings.)

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)

Cranial Bones Diagrams Whole class: Label cranial bones on the diagrams of the skull. Choose a color for each of the bones in the cranium (EX: parietal bone = red). Color the bones their assigned color in each diagram.

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