Lecture Notes: Axial Skeleton

Overview

• Focus on other bones of the axial skeleton besides the skull and facial bones.

Hyoid Bone

• Only bone in the body that doesn't articulate with another bone.
• Located in the throat, above the larynx.
• Attachment point for tongue muscles.

Vertebral Column (Spinal Column)

• Composed of 26 vertebrae divided into five regions.
• Functions: supports the body, serves as attachment point for ribs, protects the spinal cord.

Regions of the Vertebral Column

1. Cervical Vertebrae
   • Located in the neck.
   • 7 cervical vertebrae.
2. Thoracic Vertebrae
   • Located in the torso.
   • 12 thoracic vertebrae.
3. Lumbar Vertebrae
   • Located in the lower back.
   • 5 lumbar vertebrae.
4. Sacrum
   • 5 fused vertebrae.
5. Coccyx
   • 4 fused vertebrae.

Curvatures

• Cervical, thoracic, lumbar, and sacral curves (sacral sometimes referred to as scapegrum).

Intervertebral Discs

• Located between vertebrae, composed of annulus fibrosus (outer fibrous ring) and nucleus pulposus (inner pulpy nucleus).
• Function: act as shock absorbers, maintain space between vertebrae.

Vertebrae Structure

• Body: Main portion that stacks.
• Transverse Processes: Extend laterally.
• Spinous Process: Sticks out (felt as bumps along the back).
• Intervertebral Foramen: Hole for spinal nerves to exit.
• Vertebral Foramen: Central hole for the spinal cord.

Cervical Vertebrae Specifics

• Typical Cervical Vertebrae
  • Small body, bifid spinous process.
  • Transverse foramen for spinal nerves.
• Atlas (C1)
  • Articulates with occipital bone of the skull.
  • No body or spinous process.
• Axis (C2)
  • Distinctive dens (odontoid process) for pivot articulation with atlas.
  • Bifid spinous process and small body.

Thoracic Vertebrae

• Attachment areas for ribs (tubercle, superior and demi facets).

Lumbar Vertebrae

• Largest vertebrae, large body for supporting upper body weight.
• Rounded spinous process.

Sacrum and Coccyx

• Sacrum: 5 fused vertebrae, forms back of pelvic girdle.
• Coccyx: 4 fused bones, also known as the tailbone.

Sternum (Breastbone)

• Flat bone, central chest wall.
• Divided into three sections: manubrium, body, xiphoid process (Chuck Norris bone).
• Costal cartilage connects ribs to sternum.

Ribs

• 12 pairs.
• Function: support thoracic cavity, protect heart and lungs.
• Types of Ribs
  • True Ribs (1-7): Directly connect to sternum.
  • False Ribs (8-10): Connect to cartilage of ribs above.
  • Floating Ribs (11-12): Do not connect to sternum.

These notes cover the main points and details of the lecture on the axial skeleton, highlighting the different bones and their functions.