Cranial and Facial Bones Anatomy

• The skull contains 22 bones, excluding the middle ear bones.
• It serves as bony framework of the head.
• The skull rests on the superior end of the vertebral column.
• Cranial and facial bones are the two categories of skull bones.

Exterior of the Skull

• The external features are studied from five different aspects: superior, posterior, anterior, lateral, and inferior
• Norma verticalis looks at the superior aspect
• Norma occipitalis looks at the posterior spect
• Norma frontalis looks at the anterior aspect
• Norma lateralis looks at the lateral aspect
• Norma basalis looks at the inferior aspect

Cranial Bones

• There 8 cranial bones
• Cranial bones form the cranial cavity, enclose and protects the brain and provides attachments for muscles of head and neck.
• Paired cranial bones are the parietal and temporal bones.
• The unpaired cranial bones include the frontal, occipital, sphenoid, and ethmoid bones.

Facial Bones

• There are 14 facial bones.
• Facial bones form the framework of the face, contain cavities for the special sense organs and provide openings for air and food passages.
• Facial bones secure the teeth and anchor the facial muscles of expression,.
• Mandible and Vomer are unpaired facial bones
• Paired facial bones: Nasal, maxillae, zygomatic, lacrimal, palatine and inferior nasal conchae

Frontal Bone

• Forms the forehead, superior part of the orbits and part of the cranial floor.
• Frontal squama is a scale-like plate of bone
• Forms the forehead of the skull.
• Supraorbital margin is formed by the thickening of the frontal bone at the superior border of the orbits.
• Supraorbital foramina are holes within the supraorbital margin, which allow passage of arteries and nerves.
• Paranasal sinuses lie deep to the frontal squama.

Parietal Bones

• The parietal bones form the superior and lateral aspects of the skull.
• Superior and inferior temporal lines serve as the attachment for temporalis muscle.
• Protrusions and depressions on the internal surfaces of the parietal bones accommodate the blood vessels (dura mater).

Temporal Bones

• Temporal bones forms inferolateral aspects of the skull and part of the cranial floor.
• Temporal squama is a thin, flat part of the temporal bone.
• It forms the anterior and superior part of the temple.
• Zygomatic process projects from the inferior portion of the temporal squama and forms the prominence of the cheek.
• Zygomatic process articulates with the temporal process of the zygomatic (cheek) bone to form a zygomatic arch.
• Mandibular fossa (socket) located on the inferior posterior surface the zygomatic process
• A rounded elevation anterior called the articular tubercle
• Articulates with the mandible (lower jawbone) to form the temporomandibular joint.
• Mastoid portion is located posterior and inferior to the external auditory meatus or ear canal.
• Directs sound waves into the ear.
• Mastoid process is rounded projections of the mastoid portion and a point of attachment for several neck muscles.
• Internal auditory meatus is an opening which the facial (VII) and vestibulocochlear (VIII) nerve pass through.
• Styloid process projects inferiorly from temporal bone; Serves as an attachment point for muscles of the tongue and neck.
• Stylomastoid foramen lies between the styloid process and mastoid process; the facial (VII) nerve and stylomastoid artery pass through it.
• Petrous portion: triangular part located at the base of the skull; It is lies between the sphenoid and occipital bones; houses the internal ear and middle ear.
• Carotid foramen contains where the carotid artery passes through.
• Jugular foramen: passageway for the jugular vein.

Occipital Bone

• It forms the posterior aspect and base of the skull.
• The foramen magnum: inferior part of the occipital bone
• Allows passage of the spinal cord, vertebral and spinal arteries, and accessory (XI) nerve.
• Occipital condyles: oval processes on either side of the foramen magnum, and it Articulates with first cervical vertebra (atlas) to form the atlanto-occipital joint.
• The external occipital protuberance has a most prominent midline projection on the posterior surface.
• It lies just above the foramen magnum
• Superior and inferior nuchal lines contains curved ridges extending laterally from the protuberance.
• These contain areas of muscle attachment.

Sutures of the Skull

• Are immovable joints that holds skull bones together.
• Coronal suture unites the frontal bone and both parietal bones.
• Sagittal suture unites the two parietal bones on the superior midline of the skull.
• Lambdoid suture unites the two parietal bones to the occipital bone.
• Squamous sutures unite the parietal and temporal bones on the lateral aspects of the skull.

Sphenoid Bone

• Located at the middle part of the base of the skull.
• It lies posterior and slightly superior to the nasal cavity.
• Its forms posterior aspect and base of the skull
• The keystone of the cranial floor is because it articulates with other cranial bones and holds them together
• Sphenoid bone articulates anteriorly with the frontal and ethmoid bones, laterally with the temporal bones, and posteriorly with the occipital bone.
• It resembles a butterfly with a body and outstretched wings.
• The sphenoid bone contributes to the middle cranial fossa and orbits.
• The body of the sphenoid: hollowed cube-like medial portion
• Lies between ethmoid and occipital bones
• Sphenoidal sinus is the space inside the body of the sphenoid, and it drains into the nasal cavity.
• Sella turcica is a bony saddle-shaped structures on the superior surface of the body of the sphenoid.
• It projects laterally from the body
• The body located in the greater wing forms the anterolateral floor of the cranium and part of the lateral wall of the skull.
• Pterygoid processes are inferior projection from the point of body and greater wings unit.
• They form the lateral posterior region of the nasal cavity.
• Optic foramen or canal: lies between the body and lesser wing just anterior to the sella turcica; the optic (II) nerve and ophthalmic artery passes through.
• Foramen ovale is at the base of the lateral pterygoid process in the greater wing and allows passage of the mandibular nerve (branch of the trigeminal nerve).
• Foramen lacerum is bounded by the sphenoid and occipital bones and transmits the ascending pharyngeal artery.
• Foramen rotundum is located at the junction of the anterior and medial parts of the sphenoid bone, transmitting the maxillary branch of the trigeminal (V) nerve.

Ethmoid Bone

• Sponge-like in appearance and delicate bone; This located in the anterior part of the cranial floor medial to the orbits.
• It provides extensive surface area in the nasal cavity.
• Forms a part of the anterior portion of the cranial floor and medial wall of the orbits.
• It's superior portion is part of the nasal septum and most of the superior sidewalls of nasal cavity.
• Lies in the anterior floor of the cranium.
• The cribriform plate forms the roof of the nasal cavity, contains foramina contains the olfactory foramina and transmits olfactory nerves.
• Crista galli: triangular process, a superior projection from the cribriform plate, attachment point for the falx cerebri.perpendicular plate: inferior projection from the cribriform plate
• Forms the superior portion to the nasal septum
• Compose the wall between nasal cavity and orbits; contain 3 to 18 air spaces called ethmoidal cells
• Two thin, scroll-shaped projections extend laterally to the nasal septum.
• Superior nasal concha (turbinate), middle nasal concha (turbinate), and inferior nasal conchae are projections are named:

Ethmoid Bone: Conchae and Cranial Fossa

• Conchae: Increase vascular and mucous membrane surface area in the nasal cavity
• Warms and moistens inhaled air and cause inhaled air to swirl and help to trap inhaled particles.
• Superior Nasal Conchae increases the surface area for the sense of smell
• Floor of the cranial cavity: is divided into 3 distinct depressions
• Fossae accommodates a different part of the brain.
• The anterior cranial fossa is formed by the portions of the frontal, ethmoid, and sphenoid bones.
• Houses the frontal lobe of the brain.
• Features of the anterior cranial fossa include: orbital plates and frontal crest of the frontal bone and the crista galli and cribriform plate of the ethmoid bone
• The plate openings contains sensory olfactory fibers

Cranial Fossa (cont.)

• The Middle Cranial Fossa: Formed by the portions of the sphenoid and temporal bones; it houses the temporal lobe of the brain.
• Features of the Fossa: Bounded anteriorly by a ridge of the sphenoid bone and posteriorly by the petrous ridge ridge of the temporal bone
• Sella turcica - houses the pituitary gland
• Openings associated with the cranial nerves and blood vessels –foramen spinosum, the foramen ovale, the foramen rotundum, the superior orbital fissure and foramen lacerum.
• The Posterior cranial Fossa Formed mostly by the occipital bone and houses the cerebellum and occipital lobe
• Features of the Fossa = Contains foramen magnum (Hypoglossal canal for hypoglossal nerve and Jugular foramen for glossopharyngeal nerve.

Facial Bones

• The inferior nasal concha is a paired scroii-like bone
• It forms a part of the inferior lateral wall of the nasal cavity, projects into thr nasal cavity and is inferior to the middle nasal conchae of the ethmoid bone.
• NOT the part of the ethmoid bone
• Nasal Bone: paired, small, flattened, rectangular-shaped bone.
• Forms the bridge of the nose and superiorly articulates with frontal bone..
• It protects the upper entry to the nasal cavity.
• The thin muscles of facial expression attach to this bone.
• The major structural portion of the nose consists of cartilage.
• Lacrimal Bone: Paired, thin (fingernail in size and shape, smallest bone of face)
• This is posterior and lateral to the nasal bone; it houses the lacrimal sac.

Palatine Bone

• Two L-shaped bones located between the maxilla in front and the pterygoid process behind which forms
• Posterior portion of thr hard palate is shaped
• Part of the floor and lateral wall of the nasal cavity and small portion of the floors of the orbits
• Horizontal Plate - projects medially and unites with its counterpart and a portion of the posterior one-fourth of the hard palate.
• Perpendicular Plate - Fixed with the posterior part of thr medial surface of the maxilla
• Contains the greater palatine groove: vertical groove on the lateral surface of the perpendicular plate (Passage nerves and torr.)
• Triangular bone on the floor of the nasal cavity; that forms the inferior portion of the bony nasal septum.
• It articulates: Superiorly with ethmoid bone and sphenoid bones; Inferiorly with maxillae and palatine bones the the ethmoid bone
• Has the later surface, which is covered by a mucous membrane, and marked by an anteroinferior groove for nasopalatine nerve and vessels.

Bones of the Face

• Zygomatic Bone: Paired bone called cheekbones
• Forms the prominences of the cheeks
• Are the part of the lateral wall and floor of each orbit
• Arriculare.y fronta/ , maxilla, sphenoid, and tempora/ bones
• Temporal Process is a projects posteriorly that articulates to form the zygomatic arch.
• The Maxilla is a paired bone unit to form the upper jawbone, articulating with the opposite maxilla and the frontal, sphenoid, nasal, vomer, ethmoid, inferior nasal concha, palatine, lacrimal and zygomatic bones , and the septal and cartilage
• It forms the part of the floors of the orbits, lateral walls the floor of the nasal cavity and most of the palate
• It is Shaped like a pyramid, containing the maxillary paranasal sinuses;
• regions of: gives rise to 4 different
• orbit, nasal cavaity, intra temponl fossa,face The infraorbital foramen opening in the massilla infeaiour orbit - transmits the infraorbital blood vessels and mariliary division of the trigeminal nerve

Maxilla Processes

• Frontal Processes extends superiorly: Articulates with the nasal, frontal, ethmoid, and lacrimal bones; Forms the boundary of the lacrimal fossa.
• The Maxilla: Extends laterally: Articulates with the maxillary process of the Zygomatic bone.
• Alveolar Process: Ridge-like arch: Contains the alveoli for the maxillary teeth. Central (Incisor-Forms the anterior 3r4th.th. of the hard palate: Articulates with the opposite side. And the horizonal plate/process
• Bone horizontal projection of the macula and.
• Hard Palate is bony roof of the mouth, is formed by the processes of maulla and horizontal plate. It is divided into portions and it separates the nasal cavity from the oral cavity.
• Just posterior to the incisor teeth.
• The transports greater palatine vessel : Located between the wing of the th maxilla • Emptyies into the nasal cavity. fusion the failure mary bores defore beth.

Mandible (Lower Jaw Bone)

• The largest and strongest facial bone; it forms the lower jaw.
• Serves as attached point for The muscles of mastication (chewing) and the only movable skull bone.
• The has a curved , portion - The mental foramen Lhes the 2nd premolal: and nerve by dentists to inject anesthetics, or body. -Transmits lateral surface the the. us
• Lies on the the the of body Divide a a postenor borderattachment of the
• Obliquely in amuis, and antrionly to the body, passes Alveolar Nery
• ramus Meets the body that can foramen located to the
• Mandibular: angular the mandible; the begins this canals injection inject anesthetics

Mandible Details

• Coranoud Process anterier extension of each
• Aftaches the temporalis Muscles
• Procester Process of each namus Arheulates with the
• Temporamandibular Joint: Bepreesion between the corenoid and
• Alveolar Process: Bidge like arch containing the the mandibular leeth - a thick buccal and lingual le

Newborn Skull

• The most Striking feature of the Newborn Skull is the Huge size of its cranium
• It developed fast of due brain
• The reached 25% at birth and 75% by the age of 4 years
• It has the Relatively small Size of its facial Skeleton: The forms about 17th of the cranium And to their rudiment stage, maxillae.
• The non eruplron ofteeth . air sinuses • The clinically important features of the newborn skull: the Adulf bones of vault skull ossified At skullpartly.
• The Fontanelles are seen between the skullbones
• The 4 or 6 allow the Permits of the growth

Newborn Skull, Concluded

• The fontanels close.
• The anterior fontanele closes by and 2 years of age and the closes soon after
• Sphenoidal (anterolateral) fontanelles are (posterolateral) fontonelles
• The has the lateral
• theage 20 years complete rudementary Complete defvelopment

Test your knowledge of cranial and facial bones. This quiz covers bone identification, functions, and articulations. Understand the anatomy of the skull.