Anatomy of cranial bones

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22

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?

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