Study Notes on Cranium and Facial Bones

Chapter 11: Cranium

Overview of Facial Bones

  • Total of 14 bones that contribute to facial structure:

    • Right and Left Nasal Bones

    • Right and Left Lacrimal Bones

    • Right and Left Maxillary Bones

    • Right and Left Zygomatic Bones

    • Right and Left Palatine Bones

    • Right and Left Inferior Nasal Conchae

    • Vomer

    • Mandible

Anatomy: Facial Bones (1 of 2)

  • Zygoma:

    • Contributes to the prominence of the cheeks and the lateral part of the orbits.

  • Inferior Orbital Fissure:

    • An opening located within the orbit affecting nerve and blood passage.

  • Maxilla:

    • The largest immovable bone of the face, articulates with most facial bones.

  • Lacrimal Bone:

    • A thin bone, contributes to the medial wall of the orbit.

  • Nasal Bone:

    • Form the bridge of the nose.

  • Infraorbital Foramen:

    • An opening for the infraorbital nerve and artery.

  • Alveolar Process:

    • The bony ridge containing tooth sockets.

  • Mental Protuberance:

    • An anteriorly projecting portion of the mandible.

Anatomy: Facial Bones (2 of 2)

  • Maxillary Bones (1 of 3):

    • Largest immovable bones of the face.

    • Each articulates with all other facial bones except for the mandible.

    • Structure Functions:

      • Form lateral walls and the floor of the nasal cavity and part of the orbit.

  • Maxillary Bones (2 of 3):

    • Maxillary Sinus:

    • A large cavity within each maxilla.

    • Infraorbital Foramen:

    • For passage of infraorbital nerve and artery.

  • Maxillary Bones (3 of 3):

    • Anterior nasal spine and acanthion describe anatomical landmarks pertaining to the junction of bones.

Zygomatic Bones (1 of 2)

  • Prominences:

    • Contributes to the facial contour and the lateral wall and floor of the orbits.

  • Temporal Process:

    • Joins the zygomatic process of the temporal bone.

  • Zygomatic Arch:

    • Formed by the union of zygomatic and temporal processes.

Zygomatic Bones (2 of 2)

  • Articulations:

    • Superior: Frontal Bone

    • Lateral: Zygomatic Process of Temporal Bone

    • Anterior: Maxilla

    • Posterior: Sphenoid

Palatine Bones

  • Consist of two L-shaped bones with vertical and horizontal plates.

  • Functionality:

    • Horizontal plates complete the posterior fourth of the bony palate.

    • Vertical plates help form the posterior part of the nasal cavity and orbits.

Inferior Nasal Conchae

  • Thin, scroll-like bones situated in the lower part of the nasal cavity.

  • Form part of the lateral walls of the nasal cavity.

Vomer

  • A thin bone that forms the inferior part of the nasal septum.

  • Articulates with several bones, including the ethmoid bone above.

Mandible (1 of 3)

  • Largest and densest facial bone with a curved body and two rami.

  • Features:

    • Angle of Mandible (Gonion): Junction point of the body and ramus.

    • Mental Protuberance: Anterior prominence of the mandible.

Mandible (2 of 3)

  • Symphysis:

    • Central fusion point of the two halves of the mandible.

  • Alveolar Portion:

    • Area that supports teeth, superior to the body of the mandible.

  • Mental Foramina:

    • Openings for nerves and vessels located below teeth.

Mandible (3 of 3)

  • Processes:

    • Coronoid Process:

    • Anterior process for muscle attachment.

    • Condylar Process:

    • Articulates with the temporal bone to form the TMJ (temporomandibular joint).

    • Mandibular Notch:

    • Concave area between the two processes of the ramus.

Hyoid Bone

  • A U-shaped bone located at the base of the tongue.

  • Unique as it does not articulate with any other bones, classified as an accessory bone of the axial skeleton.

Bones of the Orbit

  • Comprised of seven bones:

    • Frontal, Sphenoid, Ethmoid, Maxilla, Zygoma, Lacrimal, Palatine.

Projections: Facial Bones

  • Common Projections:

    • Lateral

    • Parietoacanthial (Waters Method)

    • Modified Parietoacanthial (Modified Waters Method)

    • Posteroanterior (PA) Axial (Caldwell Method)

Lateral Facial Bones (1 of 3)

  • Patient Position:

    • Seated or recumbent in an anterior oblique position.

  • Part Position:

    • MSP (mid-sagittal plane) parallel with the image receptor (IR).

Lateral Facial Bones (2 of 3)

  • Central Ray (CR):

    • Perpendicular to the center of the IR, entering the lateral surface of the zygomatic bone.

  • Collimation:

    • To extend 1 inch above supraorbital margins and beyond anatomical shadow of the tip of the nose.

    • Maximum exposure field of 20×25 cm.

Lateral Facial Bones (3 of 3)

  • Structures Shown:

    • Lateral image of facial bones with right and left sides superimposed.

    • Evaluation criteria:

    • Side marker must be clear of anatomy.

    • All facial bones shown with zygomatic bone centered.

    • No rotation or tilt indicated by symmetrical mandibular rami and orbital roofs.

Parietoacanthial (Waters) Facial Bones (1 of 3)

  • Patient Position:

    • Prone or seated upright, with the MSP centered to midline of upright Bucky.

  • Part Position:

    • Head resting on the tip of the extended chin to form a 37-degree angle with the IR.

Parietoacanthial (Waters) Facial Bones (2 of 3)

  • CR:

    • Perpendicular to exit acanthion.

  • Collimation:

    • Extending beyond lateral sides and to include superiorly above supraorbital margins.

Parietoacanthial (Waters) Facial Bones (3 of 3)

  • Structures Shown:

    • Orbits, maxillae, zygomatic arches.

  • Evaluation Criteria:

    • Side marker must be clear, entire orbits shown, no rotation, petrous ridges projected below maxillary sinuses.

Modified Parietoacanthial (Modified Waters) (1 of 3)

  • Position:

    • Similar to Waters but with less neck extension.

Modified Parietoacanthial (Modified Waters) (2 of 3)

  • CR:

    • Perpendicular to acanthion.

  • Evaluation Criteria:

    • Detail of facial bones apparent with less axial angulation than the Waters method.

PA Axial (Caldwell) Facial Bones (1 of 4)

  • Patient Position:

    • Prone or seated upright facing vertical Bucky.

  • Position:

    • Resting forehead and nose on IR, OML perpendicular to IR.

PA Axial (Caldwell) Facial Bones (2 of 4)

  • CR:

    • Angled 15 degrees caudad, exiting at the nasion.

  • Collimation:

    • Extend beyond shadow of facial bones, above supramargins.

PA Axial (Caldwell) Facial Bones (3 of 4)

  • Structures Shown:

    • Orbital rims, maxillae, nasal septum.

PA Axial (Caldwell) Facial Bones (4 of 4)

  • Evaluation Criteria:

    • Entire facial skeleton visualized with equal symmetry.

Projected Techniques for Nasal Bones

  • Lateral Description:

    • Required positioning and CR placement described in detail for optimal viewing of nasal structures.

Routine Projections: Mandible

  • Various Techniques:

    • PA, PA axial, axiolateral oblique methods for capturing the mandible’s structure effectively, emphasizing alignment and angles.