Chapter 6 axial skeleton

Cranial bones

8; Frontal, parietal 2, temporal 2, occipital, sphenoid 2

Facial bones

14; nasal 2, zygomatic 2, maxilla 2, mandible, lacrimal 2, vomer, palatine 2, inferior nasal conchae 2

Frontal bone

Forehead, roofs of the orbits

Features: Glabella, Frontal squama, Supraorbital margins, Supraorbital foremen, Lacrimal fossa

Glabella

Most medial

Smooth part in the midline of the frontal bone between the superciliary arches (support the eyebrows)

Frontal squama

Forehead

Vertical anterior most post of the frontal bone

Supraorbital margins

Marks the superior limits of the orbits, the bony recesses that support and protect the eyeballs

Supraorbital foramen

Opening above each orbit

Transmits the supraorbital artery and nerve

Lacrimal fossa

Marks the location of the lacrimal gland (lubricates the surface of the eye)

Parietal bones 2

Curved rectangular bones

Posterolateral to the frontal bone

Sides of the cranium

Superior and inferior temporal lines- attachment of the temporalis muscle (closes the mouth)

Parietal eminence

Smooth parietal surface superior to the temporal lines

Occipital bone

Floor and back wall of the skull

Most posterior

Features: foramen magnum, occipital condyles, hypoglossal canals, basioccipital, external occipital crest and protuberance, superior and inferior nuchal lines

Foramen magnum

Hole in the base of the occipital bone

Spinal cord passes through and connects to brain

Hypoglossal canals

Passageway for hypoglossal cranial nerve XII

Begin at lateral base of each occipital condyle

Basioccipital

Band of bone anterior to foramen magnum

Articulation point between occipital bone and sphenoid bone

External occipital crest and protuberance

Midline prominences posterior to foramen magnum

Crest extends posteriorly from the foramen magnum, ending in the protuberance (small midline bump)

Superior and inferior nuchal lines

Horizontal ridges that intersect the external occipital crest

Lines mark the attachment of muscles and ligaments that stabilize the articulation between the first vertebrae C1 and the occipital condyles

Temporal bones 2

Inferior to parietal bones on the skull

4 major regions: squamous, tympanic, mastoid, petrous

Squamous region of temporal bone

Lateral surface bordering the squamous suture

Features: squama, cerebral surface, zygomatic process

Squama

Convex external surface of the region

Cerebral surface

Concave internal surface

Curvature parallels to the surface of the brain

Zygomatic process of the temporal bone

Inferior margin of the region

Curves laterally and anteriorly to meet the temporal process of the zygomatic bone to form the zygomatic arch (cheek bone)

Tympanic region of temporal bone

Surrounds external acoustic meatus

Immediately posterior and lateral to mandibular fossa

Features: Styloid process

Styloid process

Needle like projection

Inferior to external acoustic meatus

Marks attachment site for ligaments that support hyoid bone and for muscles of the tongue, pharynx, larynx

Mastoid region of temporal bone

Breast shaped area

Posterior to the ear

Features: mastoid process

Mastoid process

Rough projection

Anchors some neck muscles that rotate and extend the head

Petrous region of the temporal bone

Most massive portion of the temporal bone

Contributes to cranial base and forms lateral region of skull base

Features: jugular foramen, carotid canal, foramen lucerum, internal acoustic meatus

Jugular foramen

Passageway for the internal jugular vein (largest vein of the head) and cranial nerves IX, X, XI

Carotid canal

Inferior aspect

Anterior to jugular foramen

Passageway for internal carotid artery

Foramen lucerum

Jagged opening between the medial tip of the petrous portion of temporal bone and sphenoid bone

Almost completely closed off in living humans

Internal acoustic meatus

Posterior face of petrous region

Transmits cranial nerves VII and VIII

Sphenoid bone

Bat shaped bone

Forms anterior plateau of middle cranial fossa

Spans width of cranial floor

Features: greater wings, lesser wings, pterygoid processes, sella turcica, optic foramen, superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum

Greater wings

Form portion of the orbits of the eyes

Visible exteriorly anterior to temporal

Lesser wings

Bat shaped portion

Anterior to the sella turcica

Pterygoid processes

Vertical projections that gin at the boundary between the greater and lesser wings

Attachment sites for pterygoid muscles that move the lower jaw and soft palate

Sella turcica

Turkish saddle

Superior surface of body

Superior surface forms part of superior orbital fissure

Inferior surface forms part of orbit

Features: hypophyseal fossa, anterior chinois processes, tuberculum sellae, dorsal sellae, posterior chinois processes, optic groove, optic canal

Hypophyseal fossa

Holds pituitary gland

Anterior clinoid processes

Located on either side of sella turcica are posterior projections of the lesser wings of the sphenoid

Tuberculum sellae

Forms anterior border of the sella turcica

Dorsum sellae

Forms posterior border

Posterior clinoid processes

Extend laterally on either side of dorsum sellae

Optic groove

Transverse groove that crosses to the front of the saddle, above the seat

Optic canal

Openings at either end of the optic groove

Optic foramen

Anterior to sella turcica

CN II passes through from the orbit into the cranial cavity

Superior orbital fissure

Long slit between the greater and lesser wings

Transmits CN III, IV, VI (control eye movement)

Foramen rotundum

Lateral to sella turcica

Passage for a branch of CN V

Foramen ovale

Posterior to sella turcica

Passage for a branch of CN V

Foramen spinosum

Inferior aspect

Transmits the middle meningeal artery; supplies the broad inner surfaces of the parietal and temporal bones

Ethmoid bone

Irregularly shaped bone

Most deeply intubated bone

Located anterior to the sphenoid

Forms part of orbital wall, anteromedial floor of the cranium, the roof of the nasal cavity, and part of the nasal septum

Features: cribiform plates, ethmoidal labyrinth, perpendicular plate

Cribiform plates

Contributes to roof of nasal cavities and floor of anterior cranial fossa

Features: olfactory foramina/cribiform foramina, crista galli

Olfactory foramina/ cribiform foramina

Transmit olfactory fibers of CN I (provide sense of smell)

Crista galli

Superior projection between the 2 cribiform plates

Attached to falx cerebri (membraneous ligament); help secure the brain within the cranial cavity

Ethmoidal labyrinth

Interconnected network of ethmoidal air cells

Best viewed from anterior and posterior surfaces of the ethmoid

Features: superior and middle nasal conchae

Superior and middle nasal conchae

Thin scrolls of bony structures that contribute to the conchae of nasal cavity on either side of perpendicular plate

Perpendicular plate

Forms superior part of nasal septum

Protects inferiorly in the median plane

Superior portion is covered by olfactory epithelium

Features: lateral masses

Lateral masses

Irregularly shaped, thin walled bony regions flanking the perpendicular plate laterally

Riddled with sinuses

Cranial bone sutures

Coronal

Sagittal

Squamous

Lambdoid

Frontonasal

Occipitomastoid

Coronal suture

Parietal bones articulate with the frontal bones

Squamous suture

Parietal bones articulate with the temporal bones inferiorly

Sagittal suture

Right and left parietal bones meet

Lambdoid suture

Parietal bones articulate with occipital bone

Frontonasal suture

Boundary between the superior aspects of the two nasal bones and the frontal bone

Occipitomastoid suture

Occipital bone articulates with the temporal bones

Mandible

Lower jawbone

Features: mandibular body, rami of the mandible, mandibular angles, alveolar margin, condylar processes, coronoid processes, mandibular notch, mental foramen, mental foramina, mylohyoid line of mandible, submandibular fossa, mandibular foramina

Mandibular body

Horizatonal portion that supports the teeth

Rami of the mandible

Ascending portions from each side of the body

Mandibular angles

Thickened area that contains the alveoli and roots of teeth

Condylar processes

Posterior processes

Enlarge superior to form the mandibular condyles (heads of the mandible)

Articulate with mandibular fossae of the temporal bones to form the temporomandibular joint

Coronoid processes

Jutting anterior portion of each ramus

Site of temporalis muscle attachment

Mandibular notch

Depression that lies between the condylar and coronoid processes

Mental foramina

Prominent openings lateral to the midline

Penetrating the body on each side

Passageway for entail blood vessels and nerve that serve lower jaw

Mylohyoid line

Lies on medial aspect of body

Marking origin of the mylohyoid muscle

Submandibular fossa

Depression inferior to the mylohyoid line

Submandibular salivary gland is located

Mandibular foramina

Openings on the medial aspect of both rami

Passageway for mandibular branch of CN V (tooth sensation)

Maxillary bones 2

Largest facial bones that form the upper jaw and central part of facial skeleton

Form part of orbits

All facial bones except mandible articulate with maxilla

Features: orbital surface, palatine processes, frontal processes, zygomatic processes, inferior orbital fissure, infraorbital foramen, alveolar margins or processes

Orbital surface

Provides protection for the eye and other orbital structures

Palatine processes

Form anterior part of hard palate (bony roof of the mouth)

Frontal processes

Lateral aspect of the bridge of the nose

Articulates with the frontal bone and the nasal bones

Zygomatic processes

Articulate with zygomatic bones

Inferior orbital fissure

Elongated opening within each orbit

Formed by maxilla and the sphenoid

Infraorbital foramen

Opening under each orbit in the orbital rim

Passageway for infraorbital nerves and vessels that serve the nasal region

Alveolar margins

Oral margins of the maxilla

Contain upper teeth

Zygomatic bones 2

Lateral to the maxilla

Form the cheek bones and part of the lateral rims of the orbits

Contributes to the inferior orbital wall

Features: temporal process, zygomaticofacial foramen

Temporal process

Articulates with the zygomatic process of the temporal bone to form the zygomatic arch

Zygomaticofacial foramen

Anterior surface of each zygomatic bone

Transmits a sensory nerve innervating the cheek

Nasal bones 2

Small, rectangular bones forming the bridge of the nose

Articulates with the frontal bone at the frontonasal suture

Lacrimal bones 2

Delicate, finger nail shaped bones

Situated in the medial portion of the orbits

Articulates with the frontal bone, maxilla, and ethmoid

Features: lacrimal groove/lacrimal sulcus, nasolacrimal canal

Lacrimal groove/lacrimal sulcus

Shallow depression that leads to a narrow passageway- nasolacrimal canal

Nasolacrimal canal

Encloses the tear duct as it passes toward the nasal cavity

Palatine bones 2

Small, L shaped bones

Features: horizontal plates, perpendicular plates, nasal crest

Horizontal plates

Posterior part of hard palate

Articulate with the maxilla

Perpendicular plates

Vertical portion of L shaped bones

Posterior part of the lateral walls of the nasal cavity and small part of the orbits

Features: conchal crest, ethmoidal crest

Conchal crest

Ridge on the medial surface

Marking articulation with inferior nasal concha

Ethmoidal crest

Ridge on the medial surface

Marking the articulation with the middle nasal concha of the ethmoid

Nasal crest

Ridge that forms where the right and left palatine bone interconnect

Marking the articulation with the vomer

Vomer

Slender, plow shaped bones in the medial plane of the nasal cavity

Forms posterior and inferior portions of the nasal septum

Articulates with both the maxilla and palatine bones along the midline

Inferior nasal conchae 2

Thin, curved bones protruding medially from the lateral walls of the nasal cavity

Perform same function as the conchae of the ethmoid

Orbits of the eyes

Enclose and protect the eyes

Comprised of 7 bones of the skull: frontal bone, maxilla, lacrimal bone, ethmoid, sphenoid, palatine bone, and zygomatic bone

Nasal Cavity

Constructed of bone and cartilage

Enclose the nasal cavities and include the paranasal sinuses (air spaces connected to nasal cavity)

Frontal bone, sphenoid, ethmoid, vomer, maxillae, lacrimal, and inferior nasal conchae contribute to complex

Bridge of nose supported by maxillae and nasal bones

Paranasal sinuses

Air filled chambers that act as extensions of and open into the nasal cavities

Found in maxilla, sphenoid, ethmoid and frontal bones

Serve to lighten skull bones, produce mucus, and resonate during sound production

Hyoid bone

Not a skull bone

Superior to larynx and inferior to the skull

Only bone in the body that does not articulate with any bone

Suspended by the stylohyoid ligaments

Body and horns are attachment points for tongue and neck muscles that raise and lower the larynx during swallowing

Greater horns: larger process on the hyoid; helps support the larynx and serves as the base for muscles that move the tongue

Lesser horns: connected to the stylohyoid ligaments; hyoid and larynx hang beneath the skull- like a swing from the limb of a tree