Skull & Cranial Nerves

Question 1

Which bones compose the neurocranium?

Answer 1

Composed of calvaria (skull cap) and cranial base
Forms the shape of the head
Acts as a helmet for the brain and a scaffold of the face
Bones that make up the neurocranium ‘STEP OF’
Sphenoid
Temporal
Ethmoid
Parietal
Occipital
Frontal

Question 2

Features and location of the frontal bone.

Answer 2

Ossified in two halves which meet at the metopic suture
Contains left and right frontal air sinuses which drain into the middle meatus of the nasal cavity.

Question 3

Features and location of parietal bone

Answer 3

Form most of the cranial roof and sides of the skull
Irregular quadrilateral
Anterior border frontal margin for coronal suture
Superior articulates with the opposite parietal bone at the sagittal suture
Posterior articulates with occipital bone at lambdoid suture
Inferior articulates with temporal bone at squamous suture

Question 4

Features and location of the occipital bone

Answer 4

Convex inferiorly // concave superiorly
Allows articulation with cervical vertebra C1 at occipital condyle
Foramen magnum allows brainstem to connect to spinal cord
Provides attachments for a number of muscles in the neck and upper back
Internal occipital protuberance helps divide squamous part (houses cerebellum and occipital poles of cerebrum)

Question 5

Features and location of the temporal bone

Answer 5

Divided into 4 parts:
Squamous
Major portion with shallow mandibular fossa and zygomatic process.
Petromastoid
Petrous houses auditory apparatus and formed of compact bone. Mastoid part is trabecular with air filled spaces.
Tympanic
Forms bony external acoustic meatus and allows attachment of tympanic membrane.
Styloid process
Length varies and allows attachment site for muscles

Question 6

Features and location of sphenoid bone

Answer 6

Lies in the base of the skull between frontal, occipital, temporal and parietal bones.
Central body with paired greater and lesser wings that project laterally.
Two pterygoid processes that descend from the junction of the greater and lesser wings

Question 7

Features and location of maxillary bones

Answer 7

Largest of the facial bones other than the mandible
Both maxillae form upper jaw
Each bone forms the greater part of the floor and lateral part of the nasal cavity, and floor of orbit.
Each maxilla has a body and 4 processes
Maxillary sinus is the largest of the paranasal sinuses

Question 8

Features and location of palatine bones

Answer 8

Posteriorly placed in the nasal cavity
Sit between maxillae and ptergoid process of sphenoid bones
Contribute to floor of the orbit and the hard palate
L shaped with 3 processes (pyramidal, orbital and sphenoidal)

Question 9

Features and location of zygomatic bones.

Answer 9

Forms the prominence of the cheek
Contributes to the floor and lateral wall of the orbit
Contributes to the wall of the temporal and infratemporal fossae
Completes the zygomatic arch at the temporal process

Question 10

Features and location of lacrimal bones

Answer 10

Smallest and most fragile of the cranial bones
Lie anteriorly in medial walls of the orbits
Anterior to post lacrimal crest is a vertical grove housing the lacrimal sac

Question 11

Features and location of ethmoid bone

Answer 11

Cuboidal and fragile
Contributes to medial walls of the orbit, nasal septum, and the roof and lateral walls of the nasal cavity
Horizontal perforated cribriform plate

Question 12

Features and location of nasal bones

Answer 12

Small, oblong and variable in size and form
Found side by side between frontal processes of maxillae
Joins together at midline to form nasal bridge

Question 13

Features and location of the vomer bone

Answer 13

Thin flat bone almost trapezoid in shape
Runs vertically in the midline within nasal cavity
Forms posteroinferior portion of nasal septum
Superior border is thickest where it fits to the sphenoid bone
Prominent anterioinferior grooves for nasopalatine nerves and vessels

Question 14

Define foramen

Answer 14

Open hole that allows the passage of muscles, nerves, arteries, veins or other structures to connect one part of the body to another.
Foramen magnum allows the brainstem to connect to spinal cord
Foramen ovale in the skull

Question 15

Define fissure

Answer 15

A groove, natural division, deep furrow, elongated cleft or tear in various parts of the body
Fissure in teeth is where there is an indentation or break in the enamel
Superior orbital fissure allows passage of nerves and vessels around the orbit
Longitudinal fissure of the brain. Separates the left and right lobes in the sagittal plane.

Question 16

Define raphe

Answer 16

Greek translation of ‘seam’
Intersection of two different parts joining together at a ridged union
Palatine raphe; if this does not join together it is known as a cleft palate
Pharyngeal raphe of the pharyngeal constrictor muscles

Question 17

Define condyl

Answer 17

Latin translation of ‘knuckle’
Rounded prominence at the end of a bone
Mandibular condyle
Articular surface of head of mandible
Occipital condyle
Both condyles articulate with C1
Femoral condyle
Medial and lateral condyles of the femur at the knee joint
Articulate with the concave condyles of the tibia

Question 18

Define fossa

Answer 18

Latin translation of ‘ditch/trench’
A depression of hollow in a bone
Cranial fossa in the base of the skull
Mandibular fossa of temporal; bone allows articulation with the head of mandible