Chapter 20 (Skull, Facial Bones, & Paranasal Sinuses)

5 6

The cranium develops rapidly in size and density during the first ____-_____ years of life

Horizontal plate Vertical plate Two lateral masses (labyrinths)

The ethmoid bone consists of 4 parts:

Mastoid antrum

1st of the air cells to develop Large in size Communicates with the tympanic cavity

Perpendicular plate

A flat thin bone part of the ethmoid bone that projects inferiorly from the bottom of the cribriform plate Along with the nasal spine, forms the superior portion of the bony septum

Styloid process

A slender pointed bone of variable length, projects inferiorly, anteriorly, and slightly medially from the inferior portion of the tympanic part of the temporal bone

Ethmoid bone

A small complex shaped bone located on the midline of the skull between the orbits Forms part of the anterior cranial fossa, the nasal cavity and orbital walls, and the bony nasal septum

Nasal spine

A small inferior projection of bone located at the anterior edge of the ethmoidal notch The superiormost component of the bony nasal septum

Middle cranial fossa

Accommodates the temporal lobes and neuro-vascular structures of the brain Extends from the lesser wings of the sphenoid bone to the apices of the petrous ridges

Sphenoid bone

An irregular wedge shaped bone Resembles a bat with its wings extended

Tuberculum sellae

Anterior border of the sella turcica

Pterygoid processes

Articulates anteriorly with the palatine bones and vomer Serves as an attachment for some of the muscles that move the mandible

Frontosphenoidal suture

Articulation of the greater wing of the sphenoid bone and the squama

Frontonasal suture

Articulation of the nasal bones and the squama

Coronal suture Frontosphenoidal suture Frontonasal suture

Articulations of the frontal bone (squamous portion):

Anterior cranial fossa

Associated with the frontal lobes of the cerebrum Extends from the anterior frontal bone to the lesser wings of the sphenoid

Sphenoid bone

Bone located on the midline of the cranial floor, anterior to the temporal bones and basilar part of the occipital bone

Cranium vault

Composed of two plates of compact tissue separated by a layer of spongy tissue called Diploe (the outer layer is thicker than the inner)

Petrous pyramids

Conical or pyramidal and is the thickest densest bone in the cranium Located in the floor of the skull Houses the organs of hearing

Anterior / Middle / Posterior ethmoidal air cells

Contained by the labyrinths (lateral masses) Three divisions of air cells:

Superciliary arches

Curved ridge of bone located in the area of the eyebrows Below frontal eminences and above the supraorbital margins

Sella turcica

Deep depression on the superior surface of the body (sphenoid), houses the pituitary gland Lies 3/4" anterior and 3/4" superior to the EAM

9"

Deepest point of the skull

Mandibular fossa

Depression situated also on the inferior border of the zygomatic process Receives the condyle of the mandible and forms the TMJ

Sutures

Except for the mandible, the bones of the cranium and face are joined by fibrous joints called ______________

Optic groove

Extends across the anterior portion of the tuberculum sellae, this groove ends on each side at the optic canal

Pterygoid processes

Extensions of bone that hang from the underside of the sphenoid bone at the junction of the body and the greater wings

Immovable

Fibrous sutures of the cranium and face are classified as _______________

Mastoid Fontanel

Fontanel located at the asterion

Anterior Fontanel

Fontanel located at the junction of the two parietal bones and the frontal bone at the bregma

Posterior Fontanel

Fontanel located at the lambda

Sphenoidal Fontanel

Fontanel located at the pterion

Cranial bones

Form a protective housing for the brain

Horizontal portion (of the frontal bone)

Form the orbital plates (roofs of the orbits), part of the roof of the nasal cavity, and the greater part of the anterior fossa

Greater wings (of the sphenoid)

Forms a part of the middle cranial fossa, posterolateral walls of the orbits, lower margin of the superior orbital sulci and the greater part of the posterior margin of the inferior orbital sulci

Basilar portion (of the occipital bone)

Forms part of the base of the skull Located in front of the foramen magnum and extends anteriorly and superiorly to articulate with the body of the sphenoid bone

Occipital bone

Forms the posteroinferior wall and the floor of the cranium Articulates with the two parietals, two temporals, sphenoid, and the 1st cervical vertebra

Depressed fx

Fracture causing a portion of the skull to be pushed into the cranial cavity

Basal fx

Fracture located at the base of the skull

Contre-coup fx

Fracture to one side of a structure caused by trauma to the other side

Carotid sulcus

Groove on either side of the sella turcica where the internal carotid artery and cavernous sinus lie

Body (of sphenoid)

Hollow cubed area contains the sphenoid sinuses, sella turcica and forms the posterior bony wall of the nasal cavity

Pterygoid hamulus

Hook like process extending from the medial pterygoid

Orbital plates Ethmoidal notch Nasal spine

Horizontal portion of the frontal bone includes:

8

How many cranial bones are there?

7

How many major joints does the skull contain?

Fontanels

Infant skulls are thin and contain very small amounts of calcium. They contain six areas of incomplete ossifications called ________________

Linear fx

Irregular or jagged fracture of the skull

Foramen magnum

Large aperture contained by the squamous portion of the occipital bone through which the spinal cord passes

Squama (of the occipital bone)

Largest segment Saucer shaped, being convex externally, arise superiorly form the foramen magnum

Hypoglossal canals

Located at the anterior ends of the condyles and transmit the hypoglossal nerves

Condylar canals

Located at the posteirorend of the condyles Passageway for veins

Frontal bone

Located on the anterior aspect of the cranium Forms the forehead, superior wall (roof) of each orbit and the anterior portion of the cranial floor This single bone actually develops from two bones. The two halves fuse together by the age of 6

Greater wings (of the sphenoid)

Located posterior to the lesser wings Arises from both sides of the body of the sphenoid and curve laterally, posteriorly, anteriorly, and superiorly

Frontal sinuses

Located within the frontal bone behind the glabella

7"

Longest point of the skull

Frontal eminence

On each side of the midsagittal plane of the superior portion of the squama (forehead) is a rounded elevation called the

Articular tubercle

On the inferior border of the zygomatic process is a rounded eminence called the

Optic canal

Opening into the apex of the orbit for the transmission of the optic nerve and ophthalmic artery

Jugular foramen

Partly formed by a deep notch in the anterior portion of the occipital bone for the jugular vein and three cranial nerves to pass through

Dorsum sellae

Posterior border of the sella turcica

External occipital protuberance (inion)

Process on the midline of the squamous portion Corresponds with the internal occipital protuberance

Occipital condyles

Project anteriorly from each side of the foramen magnum on the squama for articulation with the atlas of the C spine

Zygomatic process

Prominent arched process that articulates with the zygomatic bone

Posterior cranial fossa

Protects the cerebellum, pons, and medulla oblongata The deep depression posterior to the petrous ridges

Facial bones

Provide structure, shape, and support for the face. Also provides protective housing for the upper ends of the respiratory and digestive tracts

Orbital plates

Separated by the ethmoidal notch

Ethmoidal notch

Separates the orbital plates Recieves the cribriform plate of the ethmoid bone

Crista Galli

Serves as the anterior attachment for the falx cerebri Part of the horizontal portion of the ethmoid bone (cribriform plate) Thick process that projects superiorly to extend up through the ethmoidal notch of the frontal bone

Cribriform plate

Sits into the ethmoidal notch of the frontal bone Contains many tiny foramina for the transmission of olfactory nerves

Temporal bone

Sits on each side of the base of the cranium, between the greater wings of the sphenoid and the occipital bone Forms a large part of the middle cranial fossa and small part of the posterior fossa of the cranium

Tympanic portion

Situated below the squama and in front of the mastoid and petrous portions of the temporal bones

Clivus

Slanted area of bone posterior and inferior to the dorsum sellae Continuous with the basilar portion of the occipital bone

Supraorbital foramen

Small openings for nerves and blood vessels in the center or the supraorbital margins

Anterior clinoid process

Small projections from the medial ends of the posterior borders of the lesser wings of the sphenoid Process extends from two roots: Anterior root Posterior root

Mastoid air cells

Smaller air cells develop around the mastoid antrum called the _________________

Glabella

Smooth elevation between the superciliary arches is termed the

Frontal eminences Superciliary arches Supraorbital margins Supraorbital foramens Glabella Frontal sinuses

Squamous portion of the frontal bone includes:

Lambdoidal Suture

Suture that runs between the occipital and the parietal bones

Squamosal Suture

Suture that runs between the temporal and parietal bones

1/2 inch

The EAM is approx. ___________ in length and projects medially, anteriorly, and slightly superiorly

Optic foramen

The actual opening of the optic canal is called the ________________ __________________

2nd

The anterior and mastoid fontanels close during the ________ year of life

Cranium vault

The bones of the cranium unite to form the _____________ _____________

Cranial Facial

The bones of the skull (22) are divided into what two divisions?

Frontal Occipital Right Parietal Left Parietal

The calvaria consists of? (skull cap, 4)

Optic canal

The circular opening between the two roots of the anterior clinoid process is the ____________ _____________

Calvaria Floor

The cranial bones (8) are divided into what two divisions?

3

The cranial floor is divided into _______ divisions

Ethmoid Sphenoid Right Temporal Left Temporal

The floor consists of? (4)

Foramen rotundum Foramen ovale Foramen spinosum

The greater wings of the sphenoid contain three pairs of foramen:

Cribriform plate

The horizontal portion of the ethmoid bone is also called the __________________ _________________

Bregma

The junction between the coronal and sagittal sutures

Lambda

The junction of the lambdoidal and sagittal sutures

Asterion

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

Pterion

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

Nasion

The midpoint of the frontonasal suture is termed

Parietal Temporal

The occipital bone articulates with which two cranial bones?

Squamous portion 2 occipital condyles Basilar portion

The occipital bone is divided into four parts:

Frontal Temporal Occipital Sphenoid Opposite parietal

The parietal bone articulates with the:

Parietal eminence

The parietal bone contains a prominent bulge on the lateral surface of each bone, also the widest point of the head

Petromastoid portion

The petrous and mastoid portions together are called ______________________ portions

Petrous pyramids

The petrous portion is often called the _________________ _________________

1st 3rd

The posterior and sphenoidal fontanels begin to close/ossify in the _________ and ________ month of life

Sphenoid strut

The posterior root of the anterior clinoid process is also known as the ___________ ____________ Thick and rounded

22

The skull consists of how many bones?

Body Lesser wings (2) Greater wings (2)

The sphenoid consists of three parts:

Sagittal Suture

The suture that begins just posterior to the coronal suture Runs along the top of the head between the two parietal bones

Coronal Suture

The suture that runs between the frontal and parietal bones

Squamous Tympanic Styloid process Zygomatic process Petromastoid portion

The temporal bone consists of 5 portions:

Supraorbital margins

The thick upper rim of each orbit, located just below the superciliary arches

Petrous ridges

The top ridges of the petrosa Situated at the level of the TEA

Lateral/Medial pterygoid laminae

The two plates that fuse together at their upper anterior surfaces to make up the pterygoid processes

Perpendicular plate

The vertical portion of the ethmoid bone is called the _______________ _______________

Labyrinths (lateral masses)

Thin walled sponge like structures that hang from the bottom of the cribriform plate, on either side of the perpendicular plate Forms part of the medial walls of the orbits and the lateral walls of the nasal cavity

Posterior clinoid process

Two small projections extending superiorly from the dorsum sellae

Parietal bone

Two square shaped bones that are concave internally and convex externally Form a large portion of the sides of the cranium and the roof of the cranium

Superior/Middle nasal conchae

Two thin scroll-shaped processes projecting inferiorly from each medial wall of the labyrinths

Lesser wings (of the sphenoid)

Two wings that extend laterally and horizontally from the anterosuperior aspect of the body of the sphenoid, ending in sharp points Form the posteromedial portion of the roofs of the orbits, the posterior portion of the anterior cranial fossa, the upper margin of the superior orbital fissures and the optic canals

Squamous portion

Upper portion of the temporal bone

Mastoid process

Varies considerably in size, process inferiorly to the mastoid portion of the temporal bone

Frontal squama (squamous portion)

Vertical portion of the frontal bone. Forms the forehead and the anterior part of the vault

Sphenoid bone

Which cranial bone articulates with the other 7 bones of the cranium?

6"

Widest point of the skull