Cranium, Facial Bones, and Paranasal Sinuses Lecture Review

Comprehensive vocabulary flashcards covering skull anatomy, topography, morphology, positioning lines, paranasal sinuses, facial bones, and essential radiographic projections.

Total Bones of the Skull

Composed of 22 separate bones divided into 8 cranial bones and 14 facial bones.

Subdivisions of Cranial Bones

Further subdivided into the Calvaria (skullcap) and the Floor.

Calvaria Bones

Consists of the Frontal, Occipital, Right parietal, and Left parietal bones.

Cranial Floor Bones

Consists of the Ethmoid, Sphenoid, Right temporal, and Left temporal bones.

Mesocephalic Skull

A skull of average shape where the width is between $75\%$ to $80\%$ of the length.

Brachycephalic Skull

A skull where the width is $80\%$ or more of the length.

Dolichocephalic Skull

A skull where the width is less than $75\%$ of the length.

Sutures

Fibrous joints that connect the bones of the skull, including the Coronal, Sagittal, Squamosal, and Lambdoidal sutures.

Bregma

The junction point of the coronal and sagittal sutures.

Lambda

The junction point of the sagittal and lambdoidal sutures.

Pterion

The junction of the parietal bone, squamosal suture, and the greater wing of the sphenoid.

Asterion

The junction of the occipital bone, parietal bone, and the mastoid portion of the temporal bone.

Fontanels

Areas of incomplete ossification in infant skulls, also known as 'soft spots.'

Glabella

A skull topography landmark located as the smooth area between the eyebrows.

Acanthion

A landmark located at the anterior nasal spine (the midpoint of the junction of the maxillae).

Gonion

The angle of the mandible.

Inion

The external occipital protuberance.

Orbitomeatal Line (OML)

A positioning line extending from the outer canthus of the eye to the external acoustic meatus (EAM).

Infraorbitomeatal Line (IOML)

Also known as Reid's base line, extending from the infraorbital margin to the EAM.

Frontal Bone Articulations

Articulates with the right and left parietals, sphenoid, ethmoid, nasal bones, and zygoma.

Parietal Eminence

A prominent bulge near the center of the external surface of each parietal bone used to measure the skull width for technique settings.

Foramen Magnum

A large opening in the occipital bone through which the medulla oblongata passes as it exits the cranium.

Cribriform Plate

The horizontal portion of the ethmoid bone containing numerous foramina for the olfactory nerves.

Sella Turcica

A deep depression on the superior surface of the body of the sphenoid bone that houses the pituitary gland.

Petrous Portion

Also called the petrous pyramid, it is the thickest and densest portion of the cranium and contains the organs for hearing and balance.

Auditory Ossicles

The three small bones of the middle ear: the Malleus (hammer), Incus (anvil), and Stapes (stirrup).

Eustachian Tube

The auditory tube that communicates between the middle ear and the nasopharynx to equalize pressure.

AP Axial (Towne Method) CR Angle

Directed $30$ degrees caudad to the OML or $37$ degrees caudad to the IOML.

PA Axial (Caldwell Method) CR Angle

Directed $15$ degrees caudad, exiting at the nasion.

Maxillary Sinuses

The largest and most symmetric paranasal sinuses, appearing pyramidal in shape.

Hyoid Bone

A small U-shaped bone at the base of the tongue that is the only bone in the body that does not articulate with another bone.

Symphysis Menti

The most anterior and central part of the mandible where the left and right halves fuse.

Parietoacanthial (Waters Method)

An essential facial bone projection where the OML forms a $37\text{-degree}$ angle with the plane of the IR.

Modified Waters Method

A modification where the OML is adjusted to form a $55\text{-degree}$ angle with the IR, useful for demonstrating blowout fractures.

Bones Formulating the Orbit

Composed of seven bones: Frontal, Sphenoid, Ethmoid, Maxilla, Zygoma, Lacrimal, and Palatine.

Rhese Method

A parieto-orbital oblique projection used specifically to demonstrate the optic foramina.