Head bones anatomy

• The skull is the most cranial region of the body, supported by the cervical vertebrae.
• It houses the brain, sense organs, alimentary and respiratory systems, and provides attachment for facial and neck muscles.

Structure of the Cranium

• The cranium has two divisions: The Neurocranium (brain box) and the Viscerocranium (facial skeleton).

Neurocranium

• It forms the superior and dorsal part of the cranium
• It protects the brain, meninges, and sense organs.
• The neurocranium consists of eight bones: four unpaired (median) and four paired bones.
• Unpaired bones consist of:
• Frontal
• Ethmoid
• Sphenoid
• Occipital.
• Paired bones consist of:
• Parietal
• Temporal.
• The subdivisions are calvaria (cranial vault) and cranial base.
• The calvaria is the skull's superior aspect that is formed by the frontal, parietal, temporal, sphenoid and occipital bones and consists of squamous portions.
• The cranial base includes parts of the ethmoid, frontal, sphenoid, temporal, and occipital bones.
• The boundary of the anterior cranial fossa stretches from the glabella to the external occipital protuberance.

Viscerocranium

• It forms the inferior and ventral part of the cranium.
• It houses the oral cavity, nasal cavities, paranasal sinuses, and the organs of taste and smell.
• The viscerocranium consists of 14 bones.
• Paired bones consist of:
• Nasal
• Lacrimal
• Maxilla
• Zygomatic
• Palatine
• Inferior nasal concha (turbinate).
• Unpaired bones consist of:
• Vomer
• Mandible.
• Maxilla, mandible, palatine, zygomatic, and inferior nasal concha are irregular bones.
• Nasal, lacrimal, and vomer are flat bones.

Continuity and Articulations

• The neurocranium and viscerocranium connect and articulate through synarthroses and the temporomandibular joints.
• Synarthroses are immovable joints that unite the bones into a single structure.
• The temporomandibular joints (TMJs) are synovial joints that allow movement of the mandible.

Characteristics of Cranial Bones

• Flat cranial bones are found in both the neurocranium and viscerocranium.
• Flat cranial bones consist of two compact bone tables (internal and external) separated by a spongy layer called diploë.
• Contains vascular sulci for blood vessels.
• Digitate impressions in the internal table correspond to the gyri of the brain.

Frontal View of the Cranium

• The frontal view of the cranium highlights the viscerocranium and the anterior and superior portion of the neurocranium.

Frontal Bone (Neurocranium)

• The squamous part of the frontal bone forms the forehead and the superior boundary of the frontal view.
• The frontal tuber (eminence) is the rounded prominence on each side of the forehead.
• The supraorbital margin marks the upper boundary of the orbital cavities.
• The supraorbital notch or foramen transmits the supraorbital nerve and vessels.
• Supraciliary arches are bony ridges above the orbital margins, prominent laterally.
• The glabella is the smooth midline prominence between the supraciliary arches.
• Frontonasal suture: Between the frontal bone and nasal bones.
• Frontomaxillary suture: Between the frontal bone and the frontal process of the maxilla.
• Fronozygomatic Suture: Between the frontal bone and the zygomatic bone.

Nasal Bones and Piriform Aperture (Viscerocranium)

• Nasal bones are located between the orbital cavities.
• Joined by the internasal suture, forming the superior portion of the piriform aperture (nasal cavity entrance).
• The piriform aperture is the bony opening of the nasal cavity.
• The borders of the piriform apertura consists of:
• Superiorly: Delimited by the nasal bones.
• Laterally and Inferiorly: Formed by the maxillae.
• Inferior Midline: Interrupted by the anterior nasal spine.

Maxillae

• The body of the maxillae forms the lateral and inferior portions of the piriform aperture.
• The infraorbital foramen is located below the orbit and transmits the infraorbital nerve and vessels.
• The canine fossa is a depression lateral to the infraorbital foramen, above the canine tooth.
• The palatine processes contribute to the floor of the piriform aperture and the roof of the oral cavity.
• They are joined medially by the intermaxillary suture (inferior to the anterior nasal spine).
• The alveolar processes house the roots of the upper teeth (maxillary dental arcade).
• The incisive fossa is a depression in the alveolar process near the central incisors.

Zygomatic Bones

• Zygomatic bones form the cheek prominences and lateral walls of the orbits.
• They articulate with the maxilla via the zygomaticomaxillary suture.
• They also articulate with the frontal bone via the frontozygomatic suture.

Mandible

• The Mandible is located inferiorly, below the maxillae.
• The alveolar port houses the roots of the lower teeth (mandibular dental arcade).
• Mental foramen is located laterally on the mandible, near the premolars, and transmits the associated nerve and vessels via the associated neurovascular bundles.
• The mandibular symphysis is the median ridge marking the fusion of the two halves of the mandible during development.
• It continues inferiorly as the mental protuberance, forming the chin.
• The oblique line begins laterally from the mental foramen and extends upward, forming the base of the coronoid process.

Anatomical Relations in the Frontal View

• The frontal bone articulates with the bones of the viscerocranium at the frontonasal, frontomaxillary, and frontozygomatic sutures.
• The frontal bone articulates with the nasal bones, maxillae, and zygomatic bones respectively.
• The orbital cavities dominate the central portion of the frontal view.
• The supraorbital foramen/notch exist superiorly to the orbits.
• The infraorbital foramen exists inferiorly to the orbits and the maxilla.
• The piriform aperture and nasal bones mark the superior and central portions of the nasal region.
• The alveolar processes of the maxillae and mandible define the oral region, including the dental arcades and associated fossae and foramina.

Superior View of the Cranium

• The calvaria (cranial vault) appears convex in the superior view, with a smooth, dome-like shape.
• It is composed of the squamous part of the frontal bone (anteriorly), paired parietal bones (laterally), and the squamous part of the occipital bone (posteriorly).

Cranial Bones and Sutures

• Frontal Bone (Squamous Part): Forms the anterior portion of the calvaria.
• Parietal Bones: Located laterally, these paired bones dominate the central region of the calvaria and feature the parietal tubers (eminences).
• Occipital Bone (Squamous Part: Forms the posterior portion of the calvaria and contains the external occipital protuberance.

Sutures

• The cranial bones are interconnected by jagged, dentate sutures, which provide strength and stability.
• The coronal suture exists between the frontal bone and the parietal bones.
• The sagittal suture lies on the midline, connecting the two parietal bones.
• The vertex, the highest point of the calvaria, is located approximately halfway along the sagittal suture.
• Lambdoid Suture: Joins the parietal bones with the occipital bone.

Key Landmarks

• The vertex is the highest point of the calvaria, located on the sagittal suture.
• Parietal foramina are small openings near the parietal tubers, situated on either side of the sagittal suture, and allow passage of emissary veins.
• The external occipital protuberance is a prominent bony relief on the occipital bone and is palpable externally through the skin.
• It marks the lowest point visible from the superior view of the calvaria.

Lateral View of the Cranium

• The lateral surface of the cranium includes the frontal, parietal, temporal, occipital, and sphenoid bones in addition to the zygomatic bone, maxilla, and mandible.
• Key functional areas include the temporal fossa, the zygomatic arch, and the mandible.
• The mandible articulates with the temporal bone at the temporomandibular joint (TMJ).

Temporal Region and Temporal Fossa

• The superior temporal line originates from the zygomatic process of the frontal bone.
• Separates the calvaria from the cranial base.
• The temporal fossa is inferior to the superior temporal line and borders the posterior border of the zygomatic bone, the zygomatic arch and infratemporal crest of the sphenoid.
• Houses the temporalis muscle, its nerves, and vessels, and communicates with the infratemporal fossa below the zygomatic arch.

Zygomatic Arch and Associated Structures

• Formed by the temporal process of the zygomatic bone and the zygomatic process of the temporal bone.
• Provides an attachment site as well as structural support for the masseter muscle.
• The zygomatic bone is positioned anteriorly to the temporal fossa.
• Contributes to the cheek prominence and the lateral wall of the orbital cavity.

Mandible

• The superior border of the ramus gives rise to the coronoid process, which is covered by the zygomatic arch
• Site for the attachment of the temporalis muscle
• The condylar process articulates with the temporal bone at the TMJ.
• The masseteric tuberosity is a roughened area on the ramus, located superior to the angle of the mandible.
• Provides attachment for the masseter muscle.
• The body of the mandible extends forward and curves upward into the alveolar process, housing the lower teeth.
• Contains the mental foramen near the premolars, which transmits the mental nerve and vessels.

Other Key Features of the Lateral View

• The external acoustic meatus is an opening in the temporal bone for the passage of sound waves into the ear.
• Functionally, the mastoid process serves as an attachment point for neck muscles.
• The orbital cavity opens anteriorly, bordered by the zygomatic bone and maxilla.
• Contains the structures of the eye and associated vessels and nerves.
• The body of the maxilla forms the lateral and inferior borders of the orbital cavity.
• The alveolar process houses the upper teeth.

Key Anatomical Landmarks

• The lateral view showcases the coronal, squamous, and lambdoid sutures connecting the bones of the cranium.
• The asterion denotes the junction of the parietal, temporal, and occipital bones, and marks the posterior termination of the superior temporal line.
• The mental foramen transmits the mental nerve and vessels on the mandible near the premolars.
• The external acoustic meatus is the opening in the temporal bone for the ear canal.
• The temporal fossa and zygomatic arch provides the structural support for the attachment of the temporalis and masseter muscles, which are critical for mastication

The Temporomandibular Joint (TMJ)

• The TMJ is formed by the condylar process of the mandible and the temporal bone.
• Dysfunction in the TMJ can lead to jaw pain, limited motion, and clicking sounds.

Inferior View of Cranium

• Presents both neurocranial and viscerocranial structures.
• Divided into the anterior, middle and posterior regions.

Anterior Region

• From the incisors to the posterior border of the bony palate.
  • Consists of the maxillary dental arcade, bony palate, and associated sutures such as the cruciform suture.
• Consists of the incisive fossa, greater palatine foramen, lesser palatine foramina.

Middle Region

• Includes the inferior view of the sphenoid, pterygoid processes, foramina, and temporal structures
• From the posterior palate to the anterior margin of the foramen magnum
• Structures:
  • Pterygoid Processes fo the Sphenoid
  • Medial Plate
  • Lateral Plate
  • Pterygoid Fossa
  • Foramen Ovale
  • Foramen Nodosum
  • Foramen Lacerum
  • External Acoustic Meatues
  • Styloid Process -Mandibular fossa

Posterior Region

• Occupies the occipital bone and foramen magnum.
• Contains the medulla oblongata, vertebral arteries, and accessory nerve or spinal root.
• From the foramen magnum to the external occipital protuberance.

Occipital View of the Cranium

• This reveals the structures of the neurocranium with the occipital bone, posterior portions of the parietal bones, and the mastoid processes of the temporal bones
• 1. Key Features
  • Sutures: saggital and lambdoidal
  • A prominent midline projection on the squamous part of the occipital bone that serves as an attachment site for the nuchal ligament and other soft tissues.
• Functional notes
• Important in anatomical anchorage for muscles critical to head and neck movements

Intercranial Surface of the Cranial Bone

• Surface forms the floor of the cranial cavity that divides into three cranial fossae
• Anterior fossa
• Houses the frontal lobes
• Middle fossa
• Houses the temporal lobes and pituatary region
• Sella turcia region (Turkush Saddle)
• The hypophysial fossa holds the pituitary gland
• Optic Canal:
• Transmits the optic nerve (CN II) and the ophthalmic artery to the orbit.
• Posterior fossa
• houses the cerebellum, brainstem, and associated structures
• Key Features and Openings:
• Largest opening, passage for:
• medulla oblongata.
• vertebral arteries.
• Accessory nerve (spinal root).
• dural veins.

Orbital Cavity

• Quadrangular pyramids
• The superior margin (supraorbital magin) is formed by the squamous part
• Formed by the body of the maxilla and zygomatic bone
• Houses the orbitals contents of the eye

Walls of teh Orbital Cavity

• Roof (Superior Wall)
• Formed by the orbital part of the frontal bone and lesser wings of the sphenoid.
• Floor
• Formed by orbital surface of maxilla, orbital process of perpendicular plate and orbital surface of zygomatic bone; it is a lateral surface -Medial
• Formed by frontal process of the maxilla, lacrimal bone -Lateral
• Formed by the frontal and zygomatic bone

Fissures, Foramina and Relations

• The superior orbital fissure separates the lateral wall from the roof by the lesser and greater wing of the sphenoid bone;
• 4 cranial nerves, the ophthalmic V1, and ophthalmic veins are located in the orbital bone
• Innervation of the eyelid musles and sensory for the eye orbit area as well
• Located near the inferior orbital is another passage located in the maxilla and sphenoid bone
• Serves as a pathway access to pteryopalatine and infratemporal fossae to other body parts

Cavity Relations

• Anterior Cranial Fossa, Maxillary Sinus, and Lateral Orbital areas where innervated

The Nasal Cavity

• Location that serves the respiratory function; where triangular prism are located
• Medial wall is consisted by nasal septum
• Roof by ethmoid
• Floor by platal bones

Relations of the Nasla Cavities

• Contains septum and various other structures for nasal funcgtion

Joints/Ligaments of the Cranium

• There are two joints: Synarthroses
• Fibrous joints with tight connection of cartilage
• Types:
• Serrate Sutures
• Plane Sutures
• Schindylesis
• Synchondroses
• Fused bones by catrilage which become synotsosis

Temporomandibular Joint (TMJ)

• Synovial Condylar Joint
• Synovial joint that consists of fibrous cartilage and movement coordination
• Consists of two parts
• Articular surface:
• Saddle chared and in the anterior part of the joint
• Mandibular Fossa:
• Divided into three plane for joint movement

TMJ Articular Capsule and Ligament Movement

• Movement
• Hige Movement: Mouth opening and closing
• Gliding: laterla dis[lacement
• Capsule
• Reinforcing Ligaments