U3: Skull

Concept: Skull

The study of the skull encompasses various anatomical and functional aspects of the cranial structure, including its bones, sutures, features, views, and anatomical importance.

Objectives List

  • Bones of Neurocranium

  • Sutures of Neurocranium

  • Fetal Skull

  • Anterior View of Skull

  • Lateral View of Skull

  • Inferior View of Skull

  • Cranial Floor of Skull

  • Mid-Sagittal View of Skull

  • Mandible

BONES OF THE NEUROCRANIUM

The neurocranium, also known as the cranial vault, protects the brain, houses the organs of hearing and balance, and serves as the attachment site for head and neck muscles. The neurocranium consists of the following bones:

  • 4 Singular bones:

    • Frontal bone

    • Ethmoid bone

    • Sphenoid bone

    • Occipital bone

  • 2 Sets of paired bones:

    • Temporal bones

    • Parietal bones

  • Calvarium: The domelike roof of the neurocranium.

LATERAL VIEW

In the lateral view, the following bones are visible:

  • Parietal bones

  • Occipital bone

  • Temporal bone

  • Frontal bone

Important features from this view include:

  • Temporal bone (left and right)

SUTURES OF NEUROCRANIUM

Sutures are immovable joints forming boundaries between cranial bones. The main sutures include:

  • Coronal suture: Between the frontal bone and parietal bones.

  • Lambdoid suture: Between the parietal bones and occipital bone.

  • Sagittal suture: Between the right and left parietal bones.

  • Squamous suture: Between the temporal bone and parietal bone.

FETAL SKULL

  • Fontanelles: Membranous intervals at the margins of cranial bones in fetal skulls, allowing for growth, which includes:

    • Anterior Fontanelle

    • Posterior Fontanelle

    • Sphenoid Fontanelle

ANTERIOR SKULL

The following bones are found in the anterior view:

  • Lacrimal Bone

  • Maxilla Bone (Houses teeth in the alveolar area)

  • Nasal Bone

  • Mandible

  • Zygomatic Bone

  • Vomer: Forms part of the nasal septum.

  • Perpendicular Plate of Ethmoid: Works with vomer in forming the nasal septum.

ORBITAL FEATURES

Important features in the orbital region include:

  • Infraorbital Foramen: Passage for the infraorbital nerve (Cranial Nerve V2).

  • Supraorbital Notch/foramen: Passage for the supraorbital nerve (Cranial Nerve V1).

  • Superior Orbital Fissure: Passage for cranial nerves III, IV, V1, and VI.

  • Inferior Orbital Fissure: Contains branches of cranial nerve V2.

  • Nasolacrimal Canal: Contains the nasolacrimal duct.

LATERAL VIEW OF SKULL

Key features in the lateral view:

  • Greater Wing of the Sphenoid Bone

  • Squamous Portion of the Temporal Bone

  • Zygomatic Bone

  • Zygomatic Arch: Formed by the zygomatic process of the temporal bone and temporal process of the zygomatic bone.

INFERIOR SKULL

In the inferior view, notable features include:

  • Palatine Process (of Maxilla)

  • Palatine Bone

  • Vomer

  • Carotid Canal: Passage for the internal carotid artery.

  • Occipital Condyle: Articulates with the first cervical vertebrae (atlas).

  • Mandibular Fossa: Articulates with the mandible.

  • Stylomastoid Foramen: Passage for cranial nerve VII (Facial Nerve).

CRANIAL FLOOR

Anatomical highlights of the cranial floor:

  • Lesser Wing of Sphenoid

  • Crista Galli: Attachment site for the Falx Cerebri.

  • Sella Turcica: Houses the pituitary gland.

  • Petrous Portion of Temporal Bone: Protects inner ear structures.

OPENINGS IN CRANIAL FLOOR

Openings and their importance include:

  • Jugular Foramen: Contains internal jugular vein and cranial nerves IX, X, and XI.

  • Foramen Magnum: Passage for vertebral arteries, spinal cord, and cranial nerve XI (Accessory Nerve).

  • Cribriform Plate of Ethmoid Bone: Passage for CN I (Olfactory Nerves).

MID-SAGITTAL SKULL

Components visible in a mid-sagittal view include:

  • Frontal Sinus

  • Sphenoid Sinus

  • Perpendicular Plate of Ethmoid

  • Vomer: With perpendicular plate, they form the nasal septum.

MANDIBLE

Key features of the mandible include:

  • Condylar Process: Articulates with mandibular fossa of the temporal bone.

  • Mental Foramen: Passage for the mental nerve and vessels.

  • Mandibular Foramen: Passage for the inferior alveolar nerve (location for dental anesthesia).

CONCEPT CHECKPOINTS

Throughout the guide, various check points are provided for self-assessment, where one is asked to identify specific bones or features from labeled diagrams on the skull.

These checkpoints ensure comprehension and retention of the anatomical structure and its importance in the study of the human skull.