Axial Skeleton: Skull and Vertebral Column

Section 7.1: The Skull

The skull is a complex structure composed of 8 cranial bones and 14 facial bones. It provides protection for the brain and forms the framework for the face, including the mouth, nose, and orbits.

• Cranial bones: These bones encase and protect the brain.

• Facial bones: These bones form the structure of the face and support sensory organs.

• Functions: Protection, support, and housing of sensory structures.

Section 7.2: Sutures and Individual Bones of the Skull

Sutures are immovable joints found between the bones of the skull. The major sutures include the coronal, sagittal, lambdoid, and squamous sutures.

• Sutures: Fibrous joints that connect cranial bones.

• Major sutures: Coronal, sagittal, lambdoid, squamous.

• Foramen magnum: Large opening in the occipital bone for the spinal cord.

• Sinuses: Air-filled cavities within certain skull bones that lighten the skull and enhance voice resonance.

• Paranasal sinuses: Found in the frontal, ethmoid, sphenoid, and maxillary bones.

• Functions of the hyoid bone: Supports the tongue and aids in swallowing.

• Olfactory foramina: Openings in the ethmoid bone for olfactory nerves (sense of smell).

• TMJ (Temporomandibular Joint): The joint connecting the mandible to the temporal bone, allowing jaw movement.

• Clinical Note: Temporomandibular Joint Syndrome refers to pain or dysfunction in the TMJ.

Section 7.3: Orbital and Nasal Complexes

The orbital complex protects the eyes, while the nasal complex encloses the nasal cavities. Both are formed by contributions from cranial and facial bones.

• Orbital bones: Frontal, sphenoid, ethmoid, lacrimal, palatine, zygomatic, and maxilla.

• Nasal bones: Nasal, maxilla, ethmoid, vomer, inferior nasal concha, palatine.

• Functions of paranasal sinuses: Lighten the skull, warm and moisten air, enhance resonance of voice.

Section 7.4: Fontanelles

Fontanelles are soft, non-ossified areas between cranial bones in newborns, allowing for growth and flexibility during birth and infancy.

• Major fontanelles: Anterior, posterior, sphenoidal, mastoid.

• Function: Permit rapid brain growth and facilitate passage through the birth canal.

Section 7.5: Vertebral Column and Spinal Curves

The vertebral column is a flexible structure that supports the body and protects the spinal cord. It consists of 33 vertebrae grouped into five regions and features four main curves.

• Regions: Cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused).

• Primary curves: Thoracic and sacral curves, present at birth.

• Secondary curves: Cervical and lumbar curves, develop after birth.

• Functions: Flexibility, support, shock absorption.

• Intervertebral discs: Fibrocartilaginous pads between vertebrae for cushioning and movement.

• Clinical Note: Kyphosis, Lordosis, Scoliosis are abnormal curvatures of the spine.

Table: Vertebral Column Regions and Curves

Section 7.6: Vertebral Structure and Articulations

Each vertebra has a characteristic structure, including a body, vertebral arch, and various processes. Articulations between vertebrae allow for movement and flexibility.

• Vertebral body: Main weight-bearing portion.

• Processes: Spinous, transverse, and articular processes for muscle attachment and articulation.

• Intervertebral discs: Located between vertebral bodies, composed of anulus fibrosus and nucleus pulposus.

• Facet joints: Allow for movement between vertebrae.

• Special vertebrae: Atlas (C1) and axis (C2) allow for head rotation and nodding.

Section 7.7: Thoracic Cage

The thoracic cage consists of the ribs, sternum, and thoracic vertebrae. It protects vital organs and provides attachment points for muscles involved in respiration and upper limb movement.

• Ribs: 12 pairs, classified as true (1-7), false (8-12), and floating (11-12).

• Sternum: Composed of manubrium, body, and xiphoid process.

• Functions: Protection, support, muscle attachment.

• Clinical Note: Improper CPR can fracture the xiphoid process of the sternum.

Table: Rib Classification

Key Terms and Definitions

• Suture: An immovable joint between skull bones.

• Fontanelle: Soft spot on a newborn's skull where bones have not yet fused.

• Sinus: Air-filled cavity within a bone.

• Foramen: Opening in a bone for nerves and blood vessels.

• TMJ: Temporomandibular joint, connecting jaw to skull.

• Kyphosis: Excessive outward curvature of the spine.

• Lordosis: Excessive inward curvature of the spine.

• Scoliosis: Lateral curvature of the spine.

Formulas and Equations

• Number of vertebrae:

• Rib classification:

Additional info: Some explanations and definitions have been expanded for clarity and completeness.