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Anatomy of cranial bones

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Skull is composed of how many bones?
2
How many Divisions of cranium?
8
How many Cranial bones?
14
How many Facial bones?
Calvaria (skull cap) and the floor (or base)
Cranial division forms the cranial cavity that includes:
Vomer and Mandible
Two facial bomes are classified as single bones:
Flat and Irregular
Bone classifications:
Flat
Majority of cranial bones are:
Irregular
Facial and some cranial bones
Compact tissue
Cranial vault composed of 2 plates of ___
Diploe
Both plates are separated by an inner layer of spongy tissue called ___
Thickness
Diploe varies in ___
Sutures
Join the bones of the cranium and face via fibrous joints
Sutures
Adults have ___ (rigid immovable articulations)
Coronal, Sagittal, Squamosal and Lambdoidal
4 sutures:
Coronal Suture:
Separates frontal bone from two parietals
Saggital Suture:
Located midline on top of the head, separates 2 parietal bones
Squamosal Suture:
Formed by the junctions of the parietal bones and temporal bones
Lambdoidal Suture:
Separates both parietal bones from the occipital bone
Bregma, Lambda, Pterions and Asterions
Suture junctions:
Bregma :
anterior end of the sagittal suture that intersects with the coronal suture
Pterions :
right & left located on lateral aspect of the skull where the
parietal bone, squamosal suture, and greater wing of the sphenoid meet
Lambda :
posterior end of the sagittal suture that intersects with the lambdoidal suture
Asterions :
located behind the ear at the junction of the occipital bone, parietal bone, and mastoids
Fontanels
Infants have 6 areas of incomplete ossification
Membrane-covered openings or soft spots called:
Posterior & sphenoidal fontanels
Ossification completed:End of 1st and 3rd month for __
Anterior & mastoid fontanels
Ossification completed: End of 2nd year for ___
Frontal
Singular bone of the cranium
Forehead & superior orbits
Frontal Bone contributes to the formation of the ___
Vertical and Horizontal
Frontal Bone consists of two main parts:
Vertical portion
Frontal bone part that forms the forehead
Squama
Vertical portion of the frontal bone is also called:
Orbital
Horizontal portion of frontal bone is also called ___
Horizontal portion
Portion of frontal bone that forms roofs of orbits & roof of nasal cavity
Right & left parietals
Frontal bone articulates with:
Glabella and nasion
Frontal bone includes two important structural landmarks used for central ray reference points for skull exams
Glabella
Smooth elevation between the superciliary Arches (eyebrows)
Nasion
Midpoint of the frontonasal suture
Parietal Bones
Forms lateral sides of the cranium & part of the posterior cranial roof
Right & left halves
Parietal Bones are Divided into ___
Parietal eminences (prominent bulge)
Parietal bones are the widest part of the skull located between ____
Occipital Bone
Forms posterior half of the cranial base and greater portion of the posterior cranial fossa
Squama, Occipital condyles (2) and Basilar portion
4 main parts of Occipital Bone:
Squama
Has a prominent process on its external surface, midway between its summit and the foramen magnum called the inion
Saucer-shaped
Squama is the ___ (rounded) portion that forms most of the back of the head
Occipital condyles
Oval processes that extend anteriorly on each side of the foramen magnum
Articulate with the superior facets of C1
Atlanto-occipital joint
Occipital condyles is the only two-part articulation between the skull and the cervical spine called the _____
Basilar portion
Portion of Occiptal bone that curves anteriorly & superiorly to join the body of the sphenoid bone, resulting in a continuous bone
Foramen magnum
Basilar portion that consists of a large aperature called the ___
Medulla oblongata
Basilar portion has Large opening at the base of the occipital bone through which the ___ passes as it exits the brain and joins the spinal cord
Two parietals, Two temporals, Sphenoid and Atlas (C1)
Basilar portion Articulates with six bones:
Middle fossa of the cranium & a small part of the posterior fossa
Tempral bones form a large portion of the ___
Parietal, occipital, & sphenoid
Tempral bones articulates with three cranial bones -
Temporal bones
Irregularly shaped bones located on each side of the cranial base between the occipital bone & greater wings of the sphenoid bone
Squamous, mastoid, petrous, tympanic and styloid
Temporal bones consist of five (5) main parts:
Squamous portion
Thin upper part forming part of the skull wall
Zygomatic process
Sqamous includes a prominent arched process called the ____
Temporomandibular joint (TMJ)
The inferior border of the zygomatic process contain a rounded eminence, the articular tubercle, which forms the mandibular fossa. The mandibular fossa receives the condyle of the mandible to form the ____
Mastoid portion
Posterior to EAM, forms the inferior, posterior part of the temporal bone
Air cells
Mastoid Consists of a prominent mastoid process that houses ___
Petrous pyramid
Petrous portion is also called:
Petrous portion
Thickest and densest cranial bone that Houses organs of hearing & balance
Petrous ridge
Upper border of petrous portion is referred as the;
TEA (Top of the Ear Attachment)
Top of the petrous ridge corresponds to an important external radiography landmark called the ___
IAM (Internal Acoustic Meatus)
The center of the petrous portion is the ___an opening that transmits the facial nerves & nerves of hearing & equilibrium
Tympanic portion
Temporal bone located below the squama and anterior to the petromastoid portion
EAM (External Auditory Meatus)
Tympanic portion forms the anterior, inferior, & some of the posterior wall of the __
Styloid process
A slender bony projection below the mandible & anterior to the EAM
Sphenoid bone
Irregularly wedge-shaped bone situated in the base of the cranium anterior to the temporal bone
Anchor
Sphenoid bone serves as the ___ for all eight cranial bones
Bat with its wings & legs
Sphenoid bone Resembles a ___ extended
Body, Two lesser wings, Two greater wings and Four pterygoid processes
Sphenoid Consists of four (4) primary parts:
Body
Central portion that lies in the midline in the floor of the cranium, which contains two sphenoidal sinuses
Sella turcica
Sphenoid body Includes a deep central depression called the __
Pituitary gland
Sella turcica partially surrounds & protects the ____
Clivus
Posterior to the dorsum sella is a shallow depression called the __ supports the pons (brain stem) & basilar artery
Two lesser wings
(On sphenoid) Triangular shaped & nearly horizontal wings that project laterally from the upper sphenoid bone and end medially in the anterior clinoid processes
Two greater wings
Extend laterally from the sides of the sphenoid body and form part of the cranial floor and sides of the cranium
Foramen rotundum, foramen ovale, and spinosum
____ these foramina are subject to radiographic evaluation for the detection of erosive lesions
Four Pterygoid processes
(On sphenoid) Project downward from inferior surface of the sphenoid body & form part of the lateral walls of the nasal cavity
Pterygoid hamulus
Two medial pterygoid processes or plates end in an elongated hook-shaped process called the ____
Ethmode bone
Small cubed-shaped bone
Lies between the orbits
Ethmode bone ____ & forms part of the anterior cranial fossa, nasal cavity, bony nasal septum, & orbital walls
Frontal and Sphenoid
Ethmoid bone articulates with 2 cranial bones:
Horizontal, vertical and 2 lateral labyrinths
Ethmoid bone consists of four (4) main parts:
Cribriform plate
Horizontal portion is also called:
Crista galli
Horizontal portion Includes a thick conical process called the ___, which projects superiorly & serves as an anterior attachment for falx cerebri
Perpendicular plate
Vertical portion is also called-
Bony nasal septum
Vertical portion of Ethmoid bone is athin, flat bone that projects downward in the midline, forming the ______
Masses
Two lateral labyrinths also known as:
Superior & middle nasal conchae
Projecting inferiorly from each medial wall of the labyrinth are two thin scroll shaped processes termed the ____
Flat and irregular
Skull is classified as what bones?
Pterion
What is known as the site of the antero lateral fontanel?