Bones and Ligaments of the Head and Neck

Overview of the Axial Skeleton

• Definition: The axial skeleton consists of bones situated around the longitudinal axis of the human body, following an imaginary vertical line through the center of gravity.

• Components of the Skull: The skull contains $22$ individual bones (excluding the middle ear) and sits on the superior end of the vertebral column.

The Cranial Bones

• Function: Form the cranial cavity to enclose and protect the brain.

• Bones Included:
      * Frontal bone: Forms the forehead and the roof of the eye socket.
      * Parietal bones ($2$): Form the sides and roof of the cranial cavity.
      * Temporal bones ($2$): Form the lateral aspects and inferior floor of the cranial cavity. Features include the mandibular fossa, mastoid process, and external auditory or acoustic meatus.
      * Occipital bone: Forms the posterior and base of the cranial cavity.
          * Foramen magnum: Large opening for the brainstem and spinal cord.
          * Occipital condyles: Articulate with the first vertebra for the atlanto-occipital joint (enabling nodding "yes").
          * External occipital protuberance: Midline projection for nuchal ligament attachment.
      * Sphenoid bone: Butterfly-shaped bone forming the middle base of the skull.
      * Ethmoid bone: Forms the eye socket's medial walls, the cranial floor, and the superior nasal cavity. Includes the cribriform plate and olfactory foramina for the olfactory nerve.

The Facial Bones

• Nasal bones ($2$): Small rectangular bones forming the bridge of the nose.

• Lacrimal bones ($2$): Smallest facial bones; include the lacrimal sulcus to house the lacrimal sac for tear collection.

• Maxillary bones ($2$): Form the upper jaw, most of the hard palate, and the eye socket floor.

• Zygomatic bones ($2$): Commonly known as the cheekbones.

• Mandible: The strongest facial bone; forms the lower jaw. Its mandibular condyle articulates with the temporal bone to form the temporomandibular joint.

Structural Connective Tissue and Ligaments

• Sutures: Immovable joints held by connective tissue (ligaments of the skull).
      * Coronal suture: Connects frontal and parietal bones.
      * Sagittal suture: Connects the two parietal bones.

• Nuchal Ligament: A fibrous elastic ligament extending from the external occipital protuberance to the $7th$ cervical vertebra to support the head.