Frontal bone

Frontal bone: Anatomy & FunctionKey facts about the anatomy of the frontal bone.
~ 3 min

Let us examine the structure of the frontal bone (os frontale). Its main function is protecting the frontal lobes of the brain from all kinds of damage. The bone is also involved in the formation of the orbit and the anterior cranial fossa.

Frontal bone (os frontale)
Frontal bone (os frontale)

The frontal bone consists of several parts:

  • squamous part (squama frontalis)

Squamous part (squama frontalis)
Squamous part (squama frontalis)
  • orbital part (pars orbitalis)

    Orbital part (pars orbitalis)
    Orbital part (pars orbitalis)
  • nasal part (pars nasalis)

    Nasal part (pars nasalis)
    Nasal part (pars nasalis)

    The squamous part consists of two surfaces:

  • external surface (facies externa)

    External surface (facies externa)
    External surface (facies externa)
  • internal surface (facies interna)

    Internal surface (facies interna)
    Internal surface (facies interna)

    The external surface forms what is commonly referred to as the forehead. The inferior part of the squamous part is called the supraorbital margin (margo supraorbitalis).

    Supraorbital margin (margo supraorbitalis)
    Supraorbital margin (margo supraorbitalis)

    There is a supraorbital notch (incisura supraorbitalis) on this margin closer to the nasal part. The supraorbital vessels and nerve pass here.

    Supraorbital notch (incisura supraorbitalis)
    Supraorbital notch (incisura supraorbitalis)

    In some people, this notch closes and becomes a supraorbital foramen (foramen supraorbitale).

    Supraorbital foramen (foramen supraorbitale)
    Supraorbital foramen (foramen supraorbitale)

    Medial to the supraorbital notch is a small cavity called the frontal notch (incisura frontalis). It contains blood vessels and a nerve.

    Frontal notch (incisura frontalis)
    Frontal notch (incisura frontalis)

    Around the midline on the external surface of the squamous part, there is the so-called frontal suture (sutura metopica), which is a trace of the fusion of the frontal bones in the prenatal period.

    Frontal suture (sutura metopica)
    Frontal suture (sutura metopica)

    From the supraorbital margin extends the zygomatic process (processus zygomaticus), which is connected with the zygomatic bone.

    Zygomatic process (processus zygomaticus)
    Zygomatic process (processus zygomaticus)

    A small temporal surface (facies temporalis) and temporal line (linea temporalis) can be distinguished upwards from the zygomatic process. The temporal fascia is attached to the latter.

    Temporal surface (facies temporalis)
    Temporal surface (facies temporalis)
    Temporal line (linea temporalis)
    Temporal line (linea temporalis)

    Upward from the supraorbital margin, there is the superciliary arch (arcus superciliaris). Between the left and right arches there is a protruding area — the glabella (glabella).

    Superciliary arch (arcus superciliaris)
    Superciliary arch (arcus superciliaris)
    Glabella (glabella)
    Glabella (glabella)

    Also on the external surface of the squamous part, we can distinguish a large elevation — the frontal tuber (tuber frontale).

    Frontal tuber (tuber frontale).
    Frontal tuber (tuber frontale).

    On the internal surface of the squamous part, the groove for the superior sagittal sinus (sulcus sinus sagittalis superioris) runs in the middle, which descends into the frontal crest (crista frontalis). The cranial dura mater is attached to this crest.

    Groove for the superior sagittal sinus (sulcus sinus sagittalis superioris)
    Groove for the superior sagittal sinus (sulcus sinus sagittalis superioris)
    Frontal crest (crista frontalis)
    Frontal crest (crista frontalis)

    At the base of the frontal crest lies the foramen caecum (foramen caecum).

    Foramen caecum (foramen caecum)
    Foramen caecum (foramen caecum)

    The orbital parts are sometimes called orbital plates, and they form nearly the entire superior wall of the orbit.

    The orbital part has two surfaces:

  • orbital surface (facies orbitalis)

  • cerebral surface (facies cerebralis)

Orbital surface (facies orbitalis)
Orbital surface (facies orbitalis)

The right and left orbital parts are separated by the ethmoidal notch (incisura ethmoidalis).

Ethmoidal notch (incisura ethmoidalis)
Ethmoidal notch (incisura ethmoidalis)

On the cerebral surface of the orbital parts, digitate impressions (impressiones digitatae) and impressions of cerebral gyri (juga cerebralia) can be distinguished. These are traces of adjoining of different cerebral structures.

Digitate impressions (impressiones digitatae)
Digitate impressions (impressiones digitatae)
Cerebral gyri (juga cerebralia)
Cerebral gyri (juga cerebralia)

Around the lateral angle lies the lacrimal fossa (fossa glandulae lacrimalis).

Lacrimal fossa (fossa glandulae lacrimalis)
Lacrimal fossa (fossa glandulae lacrimalis)

And closer to the center of the orbital part, we can see the trochlear fovea (fovea trochlearis), creating the attachment point of the obliquus capitis superior muscle.

Trochlear spine (spina trochlearis)
Trochlear spine (spina trochlearis)

Next to this fovea, the trochlear spine is located (spina trochlearis), to which the trochlea for the tendon of the superior oblique muscle is attached.

The nasal part of the frontal bone is located between the supraorbital margins. In front and on the sides, it bounds the ethmoidal notch. The nasal part itself is bounded laterally by the nasal margin (margo nasalis).

Nasal margin (margo nasalis)
Nasal margin (margo nasalis)

The nasal spine (spina nasalis) is derived from the nasal part.

Nasal spine (spina nasalis)
Nasal spine (spina nasalis)

The opening of the frontal sinus (apertura sinus frontalis) is located to the side of the spine (on each side).

Opening of the frontal sinus (apertura sinus frontalis)
Opening of the frontal sinus (apertura sinus frontalis)

The frontal sinus (sinus frontalis) is one of several pneumatized cranial cavities. The left and right frontal sinuses are separated by a septum.

This sinus is connected to the middle nasal meatus of the nasal cavity.

Frontal sinus (sinus frontalis)
Frontal sinus (sinus frontalis)
Dictionary

Frontal bone

frontal bone
os frontale
squamous part
squama frontalis
orbital part
pars orbitalis
nasal part
pars nasalis
external surface
facies externa
internal surface
facies interna
supraorbital margin
margo supraorbitalis
supraorbital notch
incisura supraorbitalis
supraorbital foramen
foramen supraorbitale
frontal notch
incisura frontalis
frontal suture
sutura metopica
zygomatic process
processus zygomaticus
temporal surface
facies temporalis
temporal line
linea temporalis
superciliary arch
arcus superciliaris
glabella
glabella
frontal tuber
tuber frontale
groove for superior sagittal sinus
sulcus sinus sagittalis superioris
frontal crest
crista frontalis
foramen caecum
foramen caecum
orbital surface
facies orbitalis
cerebral surface
facies cerebralis
ethmoidal notch
incisura ethmoidalis
digitate impressions
impressiones digitatae
impression of cerebral gyri
juga cerebralia
lacrimal fossa
fossa glandulae lacrimalis
trochlear fovea
fovea trochlearis
trochlear spine
spina trochlearis
nasal margin
margo nasalis
nasal spine
spina nasalis
opening of frontal sinus
apertura sinus frontalis
frontal sinus
sinus frontalis
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