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