The Axial Skeleton

Introduction to the Axial Skeleton

The axial skeleton forms the central supporting structure of the body and is essential for protection, support, and movement. It consists of the bones along the body's long axis, including the skull, vertebral column, and thoracic cage.

• Framework and Protection: The axial skeleton provides a rigid framework that supports and protects organs located in the dorsal and ventral body cavities, such as the brain, spinal cord, heart, and lungs.

• Special Sense Organs: It houses the special sense organs responsible for taste, smell, hearing, balance, and vision.

• Muscle Attachment: Serves as attachment sites for muscles that:

  • Adjust the posture of the head, neck, and trunk

  • Move the thoracic cage for respiration

  • Stabilize the appendicular skeleton

Components of the Axial Skeleton

The axial skeleton is composed of 80 bones, which can be grouped into three major regions:

• Skull (including associated bones such as the hyoid and auditory ossicles)

• Vertebral Column (spine)

• Thoracic Cage (ribs and sternum)

Example: The vertebral column not only supports the head and trunk but also protects the spinal cord and provides attachment points for ribs and muscles.

Skull and Associated Bones

Cranial and Facial Subdivisions of the Skull

The skull is a complex structure composed of cranial and facial bones. It protects the brain and forms the structure of the face.

• Cranial Bones (8): Enclose and protect the brain within the cranial cavity.

  • Frontal bone

  • Parietal bones (2)

  • Temporal bones (2)

  • Occipital bone

  • Sphenoid bone

  • Ethmoid bone

• Facial Bones (14): Form the structure of the face, support entrances to the digestive and respiratory tracts, and provide attachment points for facial muscles.

  • Maxillae (2)

  • Palatine bones (2)

  • Nasal bones (2)

  • Inferior nasal conchae (2)

  • Zygomatic bones (2)

  • Lacrimal bones (2)

  • Vomer (1)

  • Mandible (1)

• Associated Bones (7): Include the hyoid bone and auditory ossicles (malleus, incus, stapes in each ear).

Example: The mandible is the only movable bone of the skull and is essential for mastication (chewing).

Functions of the Skull

• Protection: Encloses the brain and protects it from injury.

• Support: Provides structure for the face and forms the orbits and nasal cavity.

• Attachment: Serves as attachment points for muscles involved in facial expression, chewing, and head movement.

Additional info: The skull also contains sinuses, which are air-filled spaces that reduce skull weight and contribute to voice resonance.