M3: HFN Flashcards
Paired Bones in Braincase
○ Parietal (2)
○ Temporal (2)
Unpaired Bones in Braincase
○ Frontal (1)
○ Occipital (1)
○ Sphenoid (1)
○ Ethmoid (1)
● unpaired, ‘shell-shaped’ bone that forms the anterosuperior aspect
of the cranium.
● consists of the four parts: squamous, orbital (x2), and nasal.
FRONTAL BONE
vertical groove in the midline of the frontal
bone. It contains the superior sagittal sinus.
Sagittal sulcus
○ largest component | forms the shape of the forehead
○ houses the frontal sinuses.
separated from the orbital part by the supraorbital margin.
■ contains the supraorbital foramen, where the supraorbital
vessels and nerve pass through.
SQUAMOUS PART
extension of the sagittal sulcus edges
(forms an attachment for the falx cerebri).
Frontal crest
○ small area that projects inferiorly between the supraorbital
margins.
○ area of articulation for the nasal bones and frontal processes
of the maxilla.
NASAL PART
○ Two parts
○ triangular-shaped flat plate | forms the roof of the orbit.
ORBITAL PART
bilateral skull bones that form the superior and lateral walls of the
cranium.
PARIETAL BONE
Superior | thickest and longest | Sagittal Suture
Sagittal border
Inferior | articulates with the greater wing of the
sphenoid bone and the squamous and petrous parts of
temporal bone
Squamosal border
Arteriorly | most serrated margin | comes in contact with
the frontal bone to form the superolateral half of the
coronal suture.
Frontal Border
Posteriorly | forms the inferolateral half of the lambdoid
suture by articulating with the occipital bone.
Occipital Border
● trapezoid in shape | flat, unpaired bone that forms a major part of
the posterior wall and base of the skull.
● protects the cerebellum and occipital lobes of the cerebrum
OCCIPITAL BONE
The layer of loose areolar connective tissue is known as the “danger area
of the scalp” as it contains valveless emissary veins that connect the
superficial veins in the subaponeurotic space with the intracranial venous
sinuses.
If present, the occipital emissary vein connects the occipital vein to the
union of the intracranial sinuses, making it possible for an infection to
spread from the occipital scalp to the meninges.
Infections via the “Danger Area of the Scalp”
● ‘Butterfly-shaped‘
● consists of a body, paired greater wings and lesser wings, and two
pterygoid processes.
SPHENOID BONE
a saddle-shaped depression
Sella turcica
the deepest part of the sella turcica,
where the pituitary gland is located.
Hypophyseal fossa
forms the anterior wall of the sella
turcica, and the posterior aspect of the chiasmatic groove.
Tuberculum sellae
– a sulcus formed by the optic chiasm (where the
optic nerves partially cross).
Chiasmatic groove
roof of the nasal cavity. It is pierced by numerous
olfactory nerve fibres, which gives it a sieve-like structure.
Cribriform plate
lightweight, spongy structure.
● situated at the roof of the nasal cavity, and between the two
orbital cavities.
● contributes to the medial wall of the orbit and forms part of the
anterior cranial fossa, where it separates the nasal cavity
(inferiorly) from the cranial cavity (superiorly).
● also forms a significant portion of the nasal septum and lateral
nasal wall.
● The Olfactory nerve fibres pass through the cribriform plate of the
ethmoid bone to innervate the nasal cavity with the sense of smell.
○ (this is why it looks like a sieve)
ETHMOID BONE
-projection of bone descends from the cribriform
plate | forms the superior two-thirds of the nasal septum.
Perpendicular plate
- large masses located at either side of the
perpendicular plate
Ethmoidal labyrinths (2)
