Detailed Exploration of the Skull

what are the important features of the anterior cranial fossa?

orbital plates of frontal bones, cribriform plates of ethmoid bones, crista galli

orbital plates of the frontal bones

convex elevations to either side of the cribriform plates, form the roof of the body orbit

crista galli

part of the ethmoid bone, projects upwards in the midline, provides attachment for the falx cererbi

cribriform plates of the ethmoid bone

perforated areas on either side of the crista galli, small perforations communicate with the roof of the nasal cavity below and transmit the olfactory nerve (CN I)

when looking at the anterior cranial fossa, where can the lesser wing of the sphenoid be found?

at the posterior aspect

anterior clinoid processes

part of the middle cranial fossa, extend posteriorly from the lesser wing of the sphenoid bone and provide attachments for dura

squamous portion of temporal bone

part of the middle cranial fossa, flat region

petrous portion of the temporal bone

part of the middle cranial fossa, chunky/bulky region

sella turcica of the sphenoid bone

within the middle cranial fossa, turkish saddle

tuberculum sellae

within the middle cranial fossa, front of the saddle

hypophyseal (pituitary) fossa

within the middle cranial fossa, a concavity that resembles a riders seat in the saddle and accommodates the pituitary gland

dorsum sellae

within the middle cranial fossa, back of the saddle

posterior clinoid process

within the middle cranial fossa, extends posteriorly from either end of the dorsum sellae and provides dural attachments

optic canals

within the middle cranial fossa, pass forward to the orbits and transmit the optic nerves and the ophthalmic arteries

superior orbital fissure

within the middle cranial fossa, inverted, comma shaped gap between the greater and lesser wings of the sphenoid bone found under the cover of the lesser wing that communicates with the orbit anteriorly and through which the ophthalmic veins and cranial nerves III, IV, VI, and V1 pass

foramen rotundum

within the middle cranial fossa, round opening posterior to the inferior orbital fissure that transmits the maxillary nerve (CN V2)

foramen ovale

within the middle cranial fossa, an oval shaped opening posterior to the foramen rotundum that leads to the infratemporal region below the skull and transmits the mandibular nerve (CN V3)

foramen spinosum

within the middle cranial fossa, lies immediately behind and lateral to the foramen ovale, is a small, round opening leading from the infratemporal region below that transmits the middle meningeal artery

foramen lacerum

within the middle cranial fossa, provides and opening on either side of the hypophyseal fossa for the entrance of the internal carotid artery, occupied by cartilage in life

carotid canal

found at the junction of the greater wing of the sphenoid and the petrous portion of the temporal bone

hiatus for the greater petrous nerve

within the middle cranial fossa, exits from the anterior slope of the petrous temporal ridge (the groove can be followed to the foramen lacerum), transmits the greater petrosal nerve

hiatus and groove for the lesser petrosal nerve

within the middle cranial fossa, runs parallel and inferior to the greater hiatus and groove, and leads toward the foramen ovale and transmits the lesser petrosal nerve

what structures are part of the posterior cranial fossa?

clivus, foramen magnum, hypoglossal canal, internal auditory meatus, jugular foramen, internal occipital protuberance

clivus

the body of the sphenoid bone behind the dorsum sellae which becomes fused with a portion of the occipital bone anterior to the foramen magnum, slopes posteriorly and inferiorly to end as the anterior margin of the foramen magnum

foramen magnum

large, oval shaped opening through which the spinal cord is continuous with the brainstem above

hypoglossal canal

found on the lateral margin of the foramen magnum, anterior to the occipital condyle, runs obliquely anteriorly and laterally and transmits the hypoglossal nerve (CN XII)

internal auditory meatus

lies on the posterior slope of the petrous temporal ridge just above the jugular foramen, CN VII and VIII pass through this to the middle ear region within the temporal bone

jugular foramen

a large opening lateral to the foramen magnum that leads to the base of the skull below, transmits the internal jugular vein and CN IX, X, and XI

internal occipital protuberance

internal projection of bone at the posterior pole of the internal aspect of the skull

each side of the hard palate consists of ___ bones which are the ____ and they form the ____

2

palatine process of the maxilla, forms the anterior 2/3 of the palate

horizontal plate of the palatine bone, forms the posterior 1/3 of the palate, ending posteriorly as a double crescent shaped free border

where is the intermaxillary suture found?

in the midline of the palatine processes of the maxilla, aka median palatine suture

posterior nasal spine

midline posterior projection form the posterior border of the bony palate

incisive fossa

opening of the incisive canals behind the central incisor, is the common opening for the right and left incisive canals, transmits the nasopalatine nerve and vessels

what does the greater palatine canal open as?

the greater palatine foramen and the lesser palatine foramen

greater palatine foramen

on the palatal process of the palatine bone in line with the last maxillary molar, transmits the greater palatine nerve and vessels

lesser palatine foramen

posterior to the greater palatine foramen, transmits the lesser palatine nerve and vessels

posterior nasal apertures

the posterior limits of the nasal cavity

vomer

free edge of the bony nasal septum, divides the nasal cavity into right and left nasal cavities

lateral plate of the pterygoid process of the sphenoid bone

provides attachment for both lateral and medial pterygoid muscles

medial plate of the pterygoid process of the sphenoid bone

forms the posterior limit of the lateral wall of the nasal cavity

hamulus

small, slender hook, inferior ending to the medial plate of the pterygoid process of the sphenoid bone

scaphoid fossa

canoe shaped shallow depression at the base of the medial pterygoid plate, tensor palatini muscle originates from this area

pharyngeal canal

aka palatovaginal canal, runs near the base of the vomer

pterygoid canal

passes through the base of the pterygoid process, mouth of the canal is immediately medial to the scaphoid fossa

mandibular fossa

accommodates the condyle of the mandible

tympanic plate

forms the anterior wall of the external auditory meatus and the posterior, nonfunctioning wall of the mandibular fossa

external auditory meatus

lies behind the mandibular fossa

squamotympanic fissure / petrotympanic fissure

transmits the chorda tympani nerve which is a branch of CN VII

spine of the sphenoid

a pointed projection medial to the mandibular fossa, the sphenomandibular ligament joins it to the lingula of the mandible

foramen spinosum from norma basalis

a small opening just anterior to the spine of the sphenoid, transmits the middle meningeal artery from the base of the skull to the interior of the skull

stylomastoid foramen

lies between the styloid and mastoid processes, allows passage of the facial nerve (CN VII) from within the temporal bone

styloid process

long, slender, needle-like process that points downward, forward, and medially and is joined to the lesser horn of the hyoid bone by the stylohyoid ligament, provides attachment for several muscles

entrance to the carotid canal from norma basalis

immediately anterior to the jugular foramen and separated from the jugular foramen only by a small wedge of bone

tympanic canaliculus

a small opening located inferiorly on the wedge of bone separating the carotid canal and the jugular foramen, transmits the tympanic branch of the glossopharyngeal nerve (CN IX)

what structure is labeled A?

orbital plates of the frontal bone

what structure is highlighted in orange?

crista galli

what structure is labeled B?

cribriform plate

what structure is labeled C?

lesser wing of sphenoid

what structure is labeled D?

anterior clinoid process

what structure is labeled E?

greater wing of the sphenoid

what structure is labeled F?

squamous portion of temporal bone

what structure is labeled G?

petrous portion of the temporal bone

what structure is labeled H?

tuberculum sellae

what structure is labeled I?

hypophyseal fossa

what structure is labeled J?

dorsum sellae

what structure is circled in blue?

optic canal

what structure is circled in green?

superior orbital fissure

what structure is circled in red?

foramen rotundum

what structure is circled in purple?

foramen ovale

what structure is circled in pink?

foramen spinosum

what structure is labeled K?

posterior clinoid process

what structure is circled in black?

foramen lacerum

what structure is labeled L?

carotid canal

what structure is labeled A?

clivus

what structure is labeled B?

foramen magnum

what structure is circled in blue?

hypoglossal canal

what structure is circled in yellow?

internal auditory meatus

what structure is circled in green?

jugular foramen

what structure is circled in red?

internal occipital protuberance

what structure is labeled A?

crista galli

what structure is circled in red?

sella turcica of the sphenoid bone

what structure is the black arrow pointing at?

dorsum sellae

what structure is the blue arrow pointing at?

hypophyseal fossa

what structure is the green arrow pointing at?

tuberculum sellae

what structure is labeled B / highlighted green?

lesser wing of sphenoid

what structure is highlighted in blue?

cribriform plate

what structure is highlighted in yellow?

greater wing of sphenoid

what structure is labeled A / highlighted purple?

squamous temporal bone

what structure is highlighted pink?

petrous temporal bone

what structure is highlighted in red?

crista galli

what structure is highlighted in coral?

tuberculum sellae

what structure is highlighted in purple (and not labeled A)?

hypophyseal fossa

what structure is highlighted in green?

dorsum sellae

what structure is outlined in blue?

anterior clinoid process

what structure is outlined in red?

posterior clinoid process

what structure is circled in blue?

superior orbital fissure

what structure is circled in green?

foramen rotundum

what structure is circled in red?

foramen ovale

what structure is circled in black?

foramen spinosum

what structure is labeled A?

clivus