Cranium, Facial Bones, and Paranasal Sinuses

Performing Radiographic Examination

By Hailegebriel S. (MRT, PH, MSc)

Cranium and Facial Bones and Paranasal Sinuses

Skull Anatomy

  • The anatomy of the skull is complex; attention to detail is critical in radiography.

  • Composed of:

    • 8 cranial bones

    • 14 facial bones

Cranial Bones

  • Skull divided into two areas: calvarium (skullcap) and floor.

  • Calvarium consists of:

    • Frontal

    • Right parietal

    • Left parietal

    • Occipital

  • Floor consists of:

    • Right temporal

    • Left temporal

    • Sphenoid

    • Ethmoid

Frontal Bone

  • Most visible part of calvarium; forms forehead and upper part of orbits.

  • Composed of:

    • Squamous (vertical) portion (forehead)

    • Orbital (horizontal) portion (superior part of orbit)

  • Articulates with four bones: right/left parietals, sphenoid.

Parietal Bones

  • The paired parietal bones form the lateral walls and part of the roof of the skull.

  • Articulates with five bones: frontal, occipital, temporal, sphenoid, and opposite parietal.

Occipital Bone

  • Forms the inferoposterior portion of calvarium.

  • Features:

    • Squamous portion forms most of the back of the head.

    • Foramen magnum (spinal cord exit).

  • Articulates with six bones: two parietals, two temporals, sphenoid, and atlas (first cervical vertebra).

Temporal Bones

  • Complex structures housing organs of hearing and balance.

  • Divided into three parts:

    • Squamous portion

    • Mastoid portion with mastoid process

    • Petrous portion (houses hearing/balance organs)

  • Articulates with three cranial bones: parietal, occipital, and sphenoid.

Sphenoid Bone

  • Central bone anchoring all cranial bones.

  • Features:

    • Body contains sphenoid sinus and sella turcica.

    • Articulates with all cranial and five facial bones.

Ethmoid Bone

  • The last cranial bone; lies below the cranium floor.

  • Articulates with two cranial (frontal, sphenoid) and 11 facial bones.

Sutures of the Cranium

  • Joints of the cranial bones; classified as immovable (synarthrodial) fibrous joints.

  • Types of sutures:

    • Coronal (frontal from parietals)

    • Sagittal (between parietals)

    • Lambdoidal (parietals from occipital)

    • Squamosal (parietals with temporals).

Fontanels in Infants

  • Spaces in the skull where sutures join; ossification incomplete at birth.

  • Anterior fontanel: largest, measures 2.5 cm wide at birth, closes around 18 months.

  • Posterior fontanel: found at junctions of sutures.

Facial Bones

  • 14 total:

    • 2 maxillae, 2 zygomatic bones, 2 lacrimal bones, 2 nasal bones, 2 inferior nasal conchae, 2 palatine bones, 1 vomer, 1 mandible.

Zygomatic Bones

  • Located lateral to each maxilla; forms cheek prominence and part of the orbits.

  • Articulates with three cranial bones and one facial bone (maxilla).

Nasal and Lacrimal Bones

  • Nasal bones form the bridge of the nose; vary in size.

  • Lacrimal bones are the thinnest; associated with tear ducts, articulating with two cranial and two facial bones.

Mandible

  • The largest facial bone, only movable bone in the skull.

  • Composed of ramus (vertical) and body (horizontal containing teeth).

  • Condyles articulate with temporal bones for TMJ.

Paranasal Sinuses

  • Large air-filled cavities; classified by containing bones:

    • Maxillary, frontal, ethmoid, sphenoid.

  • Important for anatomical reference and imaging purposes.

Radiographic Positioning

  • Routine and special projections with specific angles and patient positioning outlined for skull, facial bones, and paranasal sinuses.

  • Common errors include rotation, tilt, neck flexion/extension, and incorrect CR angle.

  • Correct positioning ensures accurate imaging of structures and minimizes unnecessary exposure.