Skeletal System: Axial Skeleton Study Notes (Part 2 Recap)

Skeletal System Part 2 Recap

Overview

The axial skeleton forms the central framework of the body, supporting and protecting vital organs. Key components include the hyoid bone, vertebral column, and associated ligaments and discs.

The Hyoid Bone

Structure and Function

• Definition: The hyoid bone is a U-shaped bone located in the anterior neck, between the mandible and the larynx.

• Components:

  • Greater horn: Projects posteriorly; serves as attachment for muscles of the tongue and neck.

  • Lesser horn: Smaller projections; also serve as muscle attachment sites.

  • Body: Central portion; supports the tongue.

• Function: Provides attachment for muscles associated with swallowing and speech.

• Unique Feature: Does not articulate directly with any other bone.

The Vertebral Column

General Structure

• Definition: The vertebral column (spine) is a flexible, segmented structure that supports the trunk and protects the spinal cord.

• Regions:

  • Cervical curvature: 7 vertebrae (C1–C7), concave posteriorly.

  • Thoracic curvature: 12 vertebrae (T1–T12), convex posteriorly.

  • Lumbar curvature: 5 vertebrae (L1–L5), concave posteriorly.

  • Sacral curvature: 5 fused vertebrae (sacrum), convex posteriorly.

  • Coccyx: 4 fused vertebrae.

• Functions:

  • Protects the spinal cord.

  • Supports the head and body.

  • Provides attachment for ribs and muscles.

Ligaments and Fibrocartilage Discs Uniting the Vertebrae

Key Structures

• Ligaments:

  • Supraspinous ligament: Connects the tips of the spinous processes.

  • Ligamentum flavum: Connects adjacent vertebrae; provides elasticity.

  • Anterior longitudinal ligament: Runs along the anterior surface of vertebral bodies; prevents hyperextension.

  • Posterior longitudinal ligament: Runs along the posterior surface of vertebral bodies; prevents hyperflexion.

  • Interspinous ligament: Connects spinous processes.

• Intervertebral Discs:

  • Anulus fibrosus: Outer ring of fibrocartilage; provides strength.

  • Nucleus pulposus: Gel-like center; provides cushioning and flexibility.

• Function: Ligaments and discs stabilize the vertebral column and absorb shock.

Typical Vertebral Structures

Vertebra Anatomy

• Vertebral arch: Formed by the pedicles and laminae; encloses the vertebral foramen.

• Spinous process: Projects posteriorly; site for muscle and ligament attachment.

• Transverse process: Projects laterally; attachment for muscles and ligaments.

• Superior articular facet and process: Articulates with the vertebra above.

• Vertebral foramen: Central opening for the spinal cord.

• Pedicle and lamina: Form the sides and roof of the vertebral arch.

Example: Cervical Vertebrae

• Atlas (C1): Supports the skull; allows nodding motion.

• Axis (C2): Has the dens (odontoid process); allows rotation of the head.

Additional info: The vertebral column's curvatures help maintain balance and absorb shock during movement.