Skull And Facial Bones Flashcards
what is the axial skeleton composed of?
skull bones
hyoid bone
ribs
sternum
bones of the vertebral column
How many bones does the skull consist of?
22
8 cranial and 14 facial
what do the cranial bones do?
form the cranial cavity that encloses and protects the brain
What 2 section are the skull bones divided into?
calvaria (skull cap)
floor or base
What makes up calvaria (skull cap)?
1 frontal bone
1 occipital bone
2 parietal bones
2 outer plates of compact bone
inner layer of spongy or trabecular bone called diploë
What makes up the floor or base of cranial bones?
1 ethmoid bone
1 sphenoid bone
1 occipital bone
1 frontal bone
2 temporal bones
what is the very top of the skull called?
the vertex
What are the 3 regions of the cranial floor?
anterior cranial fossa
middle cranial fossa
posterior cranial fossa
What is housed in the anterior cranial fossa?
frontal lobe of cerebrum
What is housed in the middle cranial fossa?
temporal lobes or cerebrum
What is housed in the posterior cranial fossa?
cerebellum, pons, medulla oblongata
What is the vertical part of the frontal bone?
called frontal squama (forehead)
- contains frontal sinuses
forms the forehead and anterior part of cranial vault
What is the horizontal part of the frontal bone?
orbital plates
part of roof of the nasal cavity
greater part of floor of anterior cranial fossa
How can you determine if there is any tilt in a lateral skull image?
orbital plates - will not be superimposed if there is a tilt in the image
what are the important landmarks of the frontal bone?
supraorbital margins - superior ridge of orbit
superciliary arches - eyebrows
supraorbital foramina
glabella - superior to where the eyebrows meet - smooth elevation between superciliary arches
What are the articulations of the frontal bone?
parietal bones (right and left)
sphenoid
ethmoid
nasal bones (nasion)
zygoma
what are the parietal bones?
roughly square and have a concave internal surface (convex external surface)
What is the widest part of the skull?
parietal eminences
what are the articulations of the parietal bones?
frontal
temporal
occipital
sphenoid
opposite parietal bone
what is the occipital bone?
situated at the posteroinferior part of the skull
forms the floor of the posterior cranial fossa
What are the 4 parts of the occipital bone?
squama
2 occipital condyles
- where c1 articulates with the skull
basilar portion
What are the important landmarks or the occipital bone?
External occipital protuberance (inion) - bump on middle back of skull
Nuchal lines - ridges on outside and inside of skull for muscle attachment
Foramen magnum - under side spinal cord, inside skull is spinal cord
hypoglossal canals - hypoglossal nerve (CN XII) - 12th cranial nerve passes through
Jugular foramen - internal jugular vein drains venous blood from brain
foramen lacerum
what are the jugular foramen and foramen lacerum adjacent to?
occipital bone
what are the articulations of the occipital bone?
parietal bones
temporal
sphenoid
C1
What are the temporal bones?
forms a large part of the middle cranial fossa and a small part of the posterior cranial fossa
forms the inferior lateral parts of skull
what do the temporal bones consist of?
squamous portion
tympanic portion
petrous ridges or pyramids
mastoid process
what is the squamous portion of the temporal bone?
zygomatic process of the temporal bone and temporal process of zygomatic bone form the zygomatic arch
mandibular fossa
condyle of mandible articulates with mandibular fossa to form TM joint
What is the tympanic region of the temporal bone?
inferior to squamous and anterior to mastoid and petrous bones
EAM
styloid process
what is the mastoid portion of the temporal bones?
tip of mastoid process (vertebral level of c1)
contain mastoid air cells that communicate with space in the middle ear
these air cells vary significantly in size and number
what forms the petrous portion of the temporal bones?
called petrous ridges or pyramids
project anteriorly and medially
thickest, densest bone in skull
contains the cochlea and semicircular canals
Top of ear attachment is a good landmark for the top of petrous ridges
what are the angles of the petrous ridges in the different skull shapes?
mesocephalic skull (average) - 47
brachycephalic - 54
dolichocephalic - 40
What are the important foramina of the temporal bones?
carotid canal through petrous pyramids - opens up right near foramen lacerum
- internal carotid artery - travels through the carotid canal
jugular foramen
foramen lacerum
EAM
Internal auditory canal - vestibular and facial nerves
What is the sphenoid?
keystone bone of the cranial floor - articulates with all other cranial bones holding them together
forms part of the anterior and middle cranial fossa
vaguely shaped like a bat
what does the sphenoid consist of?
1 body
2 lesser wings
2 greater wings
2 pterygoid processes
what is the body of the sphenoid?
contains 2 sphenoid sinuses
forms posterior bony wall of nasal cavity
sella turcica
what is the sella turcica?
superior surface of the body
houses the pituitary gland (hypophyseal fossa)
3/4” anterior and 3/4” superior to EAM
tuberculum sellae (anterior border)
dorsum sellae (posterior border)
- posterior clinoid processes (top border) and the clivus (which the pons sits against)
What are the lesser wings of the sphenoid?
triangular and horizontal
smaller and more superior than greater wings
What do the lesser wings of the sphenoid form?
postermedial portion of the roofs of the orbits
optic foramen - optic nerve and ophthalmic artery
upper margin of the superior orbital fissures and optic canals
anterior clinoid processes
what do the greater wings of the sphenoid form?
posterolateral walls of the orbits
lower margin of the superior orbital fissures
part of the middle cranial fossa
what do the greater wings of the sphenoid contain?
foramen ovale
foramen rotundum
foramen spinosum
what are the pterygoid processes of the sphenoid?
inferior processes off the sphenoid body and greater wings
forms the posterolateral region of nasal cavity
What is the ethmoid?
anterior to the sphenoid and posterior to nasal bones
forms a great deal of the surface area of the nasal cavity
what does the ethmoid form?
part of the anterior portion of the anterior cranial fossa
medial wall of the orbits
superior portion of nasal septum
superior portion of sidewalls of nasal cavity
what does the ethmoid consist of?
cribiform plate
cista galli
perpendicular plate
lateral masses
what is the cribiform plate?
horizontal plate
contains olfactory foramina (olfactory nerves)
What is the crista galli?
sits on cribriform plate
attachment for Falx cerebri (membrane that separates hemispheres of the brain)
what is the perpendicular plate?
forms the superior part of the bony nasal septum
what are the lateral masses?
contain the ethmoid sinuses
form the superior and middle nasal conchae
form the medial wall of orbits
what are the sutures of the skull?
fibrous, synarthrodial-type joints
1. coronal suture
2. sagittal suture
3. lambdoidal suture
4. squamosal suture
where is the coronal suture?
between frontal and parietal bones
where is the sagittal suture?
superior midline between parietal bones
where is the lambdoidal suture?
posteriorly between occipital bone and both parietal bones
where is the squamosal suture?
lateral part of skull between parietal and temporal bones
what are the important landmarks or the sutures?
- Bregma
- Lambda
- Pterions (Right and Left)
- Asterions (Right and Left)
What is the Bregma?
anterior end of sagittal suture
What is the Lambda?
posterior end of sagittal suture
What are the Pterions?
junction of the parietal, temporal and greater wing of sphenoid
landmark for the middle meningeal artery
- this is a common spot for epidural hematomas - weak spot
What are the Asterions?
Posterior to the ear where the squamosal and lamdoidal sutures meet
what does the posterior fontanel turn into in adulthood?
lambda
What does the anterior fontanel turn into in adulthood?
bregma
what do the facial bones do?
protect the entrance to the respiratory and digestive tracts
provide attachments for muscles
- facial expressions
- chewing (mastication) of food
have no contact with the brain
What are the facial bones?
nasal bones (2)
lacrimal bones (2)
maxillary bones (2)
zygomatic bones (2)
palatine bones (2)
inferior nasal conchae (2)
vomer (1)
mandible (1)
what are the nasal bones?
form the bridge of the nose
- 2 laterals when imaging - include anterior nasal spine
What are the articulations of the nasal bones?
other nasal bone
frontal bone (nasion)
maxillae
perpendicular plate of ethmoid
What are the lacrimal bones?
“tear ducts”
smallest bones in face (size and shape of a finger nail)
posterior and lateral to nasal bones
Form anterior part of medial wall of each orbit
tear duct passes through each lacrimal bone
What is the maxillary bone?
articulate with every other facial bone except the mandible
also articulates with frontal and ethmoid
what does the maxillary bone form?
part of the lateral walls and most of the floor of the nasal cavity
Part of the orbits
3/4 of the hard palate
- bony roof of mouth
- separates the nasal cavity from the oral cavity
what are the parts of the maxillae?
contains the maxillary sinuses
anterior nasal spine
- acanthion
consists of a body
4 processes come from the body
1. frontal process
2. zygomatic process
3. alveolar process
4. palatine process - forms the hard palate
What is the frontal process?
articulates with nasal bone and frontal bone
What is the zygomatic process?
articulates with zygoma
appear triangular on lateral projections of facial bones/orbits
What is the aveolar process?
articulate with 8 teeth
What is the palatine process?
require an inferior view to see
form the anterior 3/4 of hard palate
incisive foramen
articulate with palatine bones (forms other 1/4)
2 palatine processes must fuse together (cleft palate)
What is the inferior orbital fissure?
between the greater wing of sphenoid and maxilla
What is the infraorbital foramen?
below orbit
maxillary branch of the trigeminal nerve
What are the zygomatic bones (zygoma)?
form the cheek bones (malar)
what do the zygomatic bones articulate with?
frontal
temporal
sphenoid
maxillary
what forms the zygomatic arch?
temporal process of the zygomatic bone and
zygomatic process of the temporal bone
What are the palatine bones?
“L” shaped bones
Has a vertical and horizontal part
what is the vertical part of the palatine?
ascends between maxilla and pterygoid processes of sphenoid
forms posterior nasal cavity
most superior tip assists in forming posteromedial orbit
What forms the horizontal part of the palatine?
posterior 1/4 of hard palate
What is the inferior nasal conchae?
inferior lateral wall of nasal cavity
project into cavity
all 3 pairs of nasal conchae (superior, middle and inferior) increase the surface area of the nasal cavity and help swirl and filter air before it passes into the lungs
What is the vomer?
triangular bone on the floor of the nasal cavity
forms the inferior portion of the bony nasal septum
slants superiorly and posteriorly from anterior nasal spine (can fracture)
What is the mandible?
the largest, strongest facial bone
only movable skull bone
Ramus - vertical part, body - horizontal part and Angle or Gonion - between body and ramus, landmark for C3
what is the ramus?
mandibular condyle
- articulates with mandibular fossa of the zygomatic process of the temporal bone to form Temporomandibular joint (TMJ)
coronoid process
- attachment for temporalis muscle
mandibular notch is the area between the coronoid process and condyle
What is the body of the Ramus?
alveolar process
symphysis menti
mental protuberance
mental foramen
- below the 2nd premolar or bicuspid tooth
What are the TM joints?
condyle of the mandible articulates with the mandibular fossa of the zygomatic process of the temporal bone
joint is anterior and slightly superior to the EAM
Synovial, diarthrosis joint
Hinge and gliding
Images are acquired with the mouth open and closed
Amount condyle moves is termed excursion
What are the paranasal sinuses?
air-filled structures that all communicate with nasal cavity
- frontal sinuses
- sphenoid sinuses
- ethmoid sinuses
- maxillary sinuses
what is the purpose of the paranasal sinuses?
resonating chamber for the voice
decrease weight of skull
help warm and moisten inhaled air
act as schock absorbers in trauma (air bags)
What are the frontal sinuses?
second largest group
located between the 2 tables of squama
typically 2
vary greatly in size and shape
What are the sphenoid sinuses?
typically 2 sinuses in body of the sphenoid
What are the ethmoid sinuses?
lateral masses of ethmoid
divided into three different groups: anterior, middle and posterior
What are the maxillary sinuses?
largest
in the body of the maxillae
floor of the sinus is called maxillary antrum
frontal view they appear pyramid-shaped
Lateral view they appear more cube shaped
What is the position for the waters method?
looking up and opening mouth to see the sphenoid sinuses through the mouth
What are the orbits composed by?
3 cranial bones and 4 facial bones
What are the cranial bones that make up the orbit?
frontal, sphenoid and ethmoid
What are the facial bones that make up the orbit?
palatine, zygomatic, lacrimal and maxillary
What bones make up the circumference of the orbit?
frontal, zygomatic and maxillary
What makes up the roof of the orbit?
mainly frontal bone (orbital plates) and lesser wing of the sphenoid
What makes up the floor of the orbit?
Maxillary, zygomatic and palatine
site of blowout fractures - maxilla - bleeding into maxillary sinus
What makes up the medial wall of the orbit?
ethmoid, lacrimal and maxillary
thinnest portion
What makes up the lateral wall of the orbit?
frontal process of zygomatic, greater wing of sphenoid
thickest part for protection
What is the Hyoid?
part of the axial skeleton
does not articulate with any other bone
“U” shaped
Suspended from the styloid processes of the temporal bones by muscles and ligaments
located in the anterior part of the neck between mandible and larynx
supports the tongue
may be fractured during strangulation
