Axial Skeleton: Skull

skull, vertebral column, and rib cage

the axial skeleton consists of…

8 cranial bones

how many cranial bones are there?

14 facial bones

how many facial bones are there?

calvaria

the roof of the cranial cavity

nasal septum

the bone and cartilage that divides the nasal cavity in half

spheniodal, maxillary, frontal, ethmoidal

what are the four paranasal cavities?

maxillary sinus; it drains at the top

which sinus is the most commonly infected?

frontal bone

the bone located at the anterior roof of the cranium

supraorbital margin

the prominent bony ridges over the orbits, typically covered in hair

supraorbital foramen

a hole at the midpoint of each supraorbital margin, that allows for passage of small nerves and blood vessels

frontal sinuses

sinuses that are shaped like a butterfly, not everyone has, and are a unique biological identifier

frontal crest

a ridge on the internal anterior surface of the frontal bone that is the anterior attachment site for the falx cerebri

falx cerebri

a sickle shaped sheet of connective tissue that partially separates the left and right sides of the brain

parietal bones

paired bones forming the lateral walls and roof of the cranium

sagittal suture

the midline suture that divides the left and right parietals

coronal suture

the suture that separates the parietal bones from the frontal bone

temporal bones

paired bones that form the lower sides and part of the floor of the cranium

squamosal suture

the suture that divides the temporal bones from the parietal bones

petrous region

the region of the temporal bone that houses the structure of the middle and inner ear

internal auditory canal (internal acoustic meatus)

the space that allows nerves and blood vessels to travel to and from the inner and middle ear

otitis media

infection of the middle ear

carotid canal

a space that allows the entry of the internal carotid artery into the cranial cavity

foramen lacerum (FLOST)

an opening that is closed off by connective tissue in a living person, and is located between the petrous portion of the temporal bone, the sphenoid bone, and the occipital bone

jugular foramen

an opening just posterior to the carotid canal, and allows blood to drain from the brain via the internal jugular vein

mastoid region

a region of the temporal bone that is a rounded projection and can be felt behind the ear

mastoid process

the large bony part of the temporal bone that allows for muscle attachment that can flex the neck or rotate the head

mastoiditis

an infection of the mastoid bone, due to prolonged otitis media

squamous region

the region of the temporal bone that is the lateral flat surface directly inferior to the squamosal suture

zygomatic process

the forward projection of the temporal bone that forms the posterior portion of the zygomatic arch

mandibular fossa

the inferior portion of the squamous region that receives the articulating condyle of the mandible

temporomandibular joint (mandibular condyle)

the condyle that articulates with the mandibular fossa of the temporal bone

tympanic region

the region of the temporal bone that is a small area surrounding the outer entrance to the external auditory canal

styloid process

the spiney process just inferior to the tympanic region that serves as a muscle attachment site for several muscles associated with the tongue and hyoid bone

occipital bone

the bone that forms the back and much of the base of the skull

lambdoidal suture

the suture that separates the occipital bone from the parietal bones

foramen magnum

the large opening at the base of the occipital bone that the spinal cord passes through to attach to the brain

occipital condyles

the rounded knobs on each side of the foramen magnum that articulate with the atlas vertebrae, they work as a “rocking chair” and allow the head to nod yes

nuchal lines (superior and inferior)

the two prominent horizontal ridges on the posterior of the occipital bone that are attachment sites for neck muscles

internal occipital crest

a ridge on the internal posterior surface of the occipital bone that is the posterior attachment site for the falx cerebri

sphenoid bone

the bone that contributes to the base of the skull and resembles a bat, sometimes it is referred to as the bridge bone because it connects several facial and cranial bones

sella turcica

the prominent depression on the superior medial portion of the sphenoid bone that holds the pituitary gland

head into the dashboard syndrome

when trauma to the brain sends it forward, severing the pituitary stalk

optic foramen

a foramen in the sphenoid bone that allows passage of the optic nerve (CN II)

foramen rotundum

a foramen in the sphenoid bone that allows for passage of the second branch of the trigeminal nerve (CN V) that conveys sensations from the teeth and gums of the maxillae

foramen ovale

a foramen in the sphenoid bone that allows for passage of the third branch of the trigeminal nerve (CN V) that conveys sensation from the teeth and gums of the mandible

foramen spinosum

a foramen in the sphenoid bone that is a small opening for meningeal blood vessels

superior orbital fissure

a foramen in the sphenoid bone that allows for passage of several cranial nerves including the first branch of the trigeminal nerve (CN V) that conveys sensation to the nose, forehead, and anterior scalp

pterion

the portion of the sphenoid bone that articulates with the frontal, parietal, and temporal bones and is named after Hermes wings, this is the weakest part of the skull, and the middle meningeal artery runs underneath

ethmoid bone

the bone that is located in the anterior portion of the floor of the cranium between the orbits

crista galli (cock’s comb)

the midsagittal elevated superior part of the ethmoid bone, and is an anterior attachment site for the falx cerebri

cribriform plates

the parts of the ethmoid bone lateral to the crista galli that have numerous foramina that allow passage of fibers for the olfactory nerves (CN I) to travel from nose to brain

meningitis

fracture and leakage of of spinal fluid following trauma to the face, allowing bacteria to enter the meninges

perpendicular plate

the superior part of the nasal septum, the inferior midline projection of the ethmoid bone that divides the nasal cavity

conchae (turbinates)

two projections of the ethmoid bone on the lateral walls of the nasal cavity

superior nasal conchae and middle nasal conchae

the two projections of the ethmoid bone on the walls of the nasal cavity

erectile tissue

what are nasal conchae made of?

nasal cycle

the turbinates in on fossa fill up with blood while the opposite turbinates decongest by shunting blood away, this cycle is usually 2.5 hours, but varies

zygomatic bones

paired facial bones that form the bony prominence of the cheeks and contribute to the lateral margin of the orbits

zygomatic arch

formed by the articulation of the temporal process of each zygomatic bone with the zygomatic process of each temporal bone

lacrimal bones

paired facial bones that form part of the medial wall of each orbit

lacrimal groove

a passageway for the nasolacrimal duct that drains tears into the nasal cavity

nasolacrimal duct

the duct that opens into the nasal cavity just inferior to the inferior nasal conchae

nasal bones

paired facial bones from the bridge of the nose, support the lateral cartilages

vomer bone

the single facial bone that has a triangular shape and resembles a plow, it contributes to the posterior portion of the nasal septum

inferior nasal conchae

paired facial bones that project into the nasal cavity just below the superior and middle nasal conchae

palatine bones

paired facial bones that are small with an L shape, and form the posterior third of the hard palate

maxillae bones

paired facial bones that unite at the midline to form the upper jaw, they form the anterior portion of the hard palate

• anterior portion of the face

• anterior portion of hard palate

• anterior floor and walls of nasal cavity

• inferior parts of the orbits

What parts of the face do the maxillae support?

infraorbital foramen

the foramen located just under the eye, part of the maxillae

palatine processes

projections of the maxillae that move horizontally from the anterior portion of the hard palate

cleft palate

palatine processes fail to join during early prenatal development

maxillary sinus

sinuses that lay lateral to the nasal cavity which drain into the nasal cavity through an opening high and medial within the sinus that exits just inferior to the middle nasal conchae

crepitus

a crackling sound caused by gas or broken bone under the skin

blowout fracture

blows to the eye and orbit that may fracture the floor of the orbit causing the eye, or the muscles to drop down into the maxillary sinus

mandible bone

facial bone that forms the entire lower jaw

body of mandible

the large horseshoe shaped portion of the mandible that is the front and lateral sides

mentum

the anterior point of the body of the mandible

rami (ramus)

the vertical extending portions of the mandible that form the posterior portion of the body

mandibular condyle

the condyle that articulates with the mandibular fossa of the inferior squamous portion of the temporal bone

coronoid

a pointed process of the mandible that allows for muscle attachment that closes the jaw

mandibular notch

the U-shaped depression between the coronoid and mandibular condyle of the mandible

mental foramen

the foramen that penetrates the body of the mandible on each side of the chin for passage of nerves and blood vessels

mandibular foramen

the foramen which penetrate the medial side of each ramus and allows passage of the third branch of the trigeminal nerve

third division nerve block

an injection of anesthetic near the mandibular foramen that will desensitize the mandibular teeth and gums

nasal bones, cribriform plate of ethmoid, parts of the frontal and sphenoid bones

roof of nasal complex

palatine processes of maxillae and the horizontal plates of the palatine bones

floor of the nasal complex

ethmoid bone, maxillae, inferior nasal conchae, palatine bones, and lacrimal bones

lateral walls of the nasal complex

perpendicular plate of ethmoid bone, vomer, and septal cartilage (hyaline cartilage)

nasal septum

• maxillae

• palatine

• sphenoid

• zygomatic

• frontal

• lacrimal

• ethmoid

• (Mandy Purposely Sees Zebras Falling Like Elephants)

what bones contribute to the orbital complex?

• malleus (hammer)

• incus (anvil)

• stapes (stirrup)

what are the auditory ossicles

hyoid bone

the slender, U-shaped bone located inferior to the skull between the mandible and the larynx, it is suspended by ligaments and is commonly fractured in strangulation homicides

5 years

what age is the skull mostly grown by?

fontanelles (soft spots)

the large membranous areas of the skull that provide spaces between the developing bones

molding

the shifting of cranial bones during parturition that causes a temporary cone head, one parietal bone typically overlaps the other and the occipital bone slides underneath

dehydration (sunken) or meningitis (bulging)

what causes sunken or bulging fontanelles?

dental attrition

the wear down and loss of teeth during aging

1. coronal

2. sagittal

3. lambdoidal

4. squamosal may or may not fuse before death

in what order do the cranial sutures fuse and become ossified?

Rene LeFort

the man who classified the LeFort fractures

LeFort I fracture (horizontal maxillary fracture)

a horizontal fracture through the pterygoid plates and maxillary bone between the hard palate and orbits

LeFort II fracture (pyramidal fracture)

a fracture line from one of the lateral vertical buttresses across the maxillary bone, extending into the inferior orbital rim and crossing the midline