Axial Skeleton Study Notes (Lab 2)

Skeletal System Overview

• Axial skeleton: $80$ bones
• Appendicular skeleton: $126$ bones
• 5 major functions of the skeletal system:
  • Body support
  • Body movement
  • Organ protection
  • Mineral storage
  • Blood cell production

Classification and Markings of Bones

• Projections: processes that grow out from the bone
  • Functions: muscle attachment, joint formation
• Depressions: indentations or openings in the bone
  • Functions: conduits of nerves and blood vessels

Long Bone Anatomy

• Regions and features:
  • Proximal epiphysis
  • Spongy bone with red bone marrow
  • Medullary cavity
  • Yellow bone marrow
  • Epiphyseal plate
  • Compact bone
  • Periosteum
  • Diaphysis
  • Periosteal blood vessel
  • Distal epiphysis
  • Perforating Sharpey fibers
  • Periosteum
• Osteon structure:
  • Central canal
  • Perforating Volkmann’s canal
  • Compact bone
  • Spongy bone
  • Blood vessel continues into medullary cavity containing marrow

Axial Skeleton Overview

• Axial skeleton counts: $80$ bones
• Skull and associated bones: $29$
  • Cranium: $8$ bones
  • Occipital, frontal, 2 temporal, 2 parietal, sphenoid, ethmoid
  • Face: $14$ bones
  • 2 palatine, 2 maxillary, 2 nasal, 2 zygomatic, 2 inferior nasal conchae, 2 lacrimal, vomer, mandible
• Thoracic cage: $25$ bones
  • Associated bones: $7$
  • 6 auditory ossicles, hyoid
• Vertebral column: $26$ bones
• Sternum: $1$ bone
• Ribs: $24$ bones
• Vertebrae: $24$ bones
  • 7 cervical, 12 thoracic, 5 lumbar
• Memorization aid (to memorize vertebral counts): I eat breakfast at $7$, have lunch at $12$, and eat dinner at $5$.

Cranial Bones

• Frontal
• Parietal (2)
• Temporal (2)
• Occipital
• Sphenoid
• Ethmoid

Facial Bones

• Vomer bone
• Zygomatic bones (2)
• Lacrimal bones (2)
• Nasal bones (2)
• Inferior nasal conchae (2)
• Palatine bone (2)
• Maxilla (2)
• Mandible

Cranial Nerves

• Olfactory nerve
• Optic nerve
• Oculomotor nerve
• Trochlear nerve
• Trigeminal nerve
• Abducens nerve
• Facial nerve
• Vestibulocochlear nerve
• Glossopharyngeal nerve
• Vagus nerve
• Spinal accessory nerve
• Hypoglossal nerve
• Sequence by nerve numbers: I II III, IV, V, VI V VII, VIII IX, X, XI XII

Thoracic Cage

• Sternum
  • Manubrium
  • Sternal body
  • Xiphoid process
• Ribs
  • True ribs: $R1-R7$
  • False ribs: $R8-R12$
  • Floating ribs: $R11-R12$

Vertebral Column

• Cervical vertebrae: $7$
• Thoracic vertebrae: $12$
• Lumbar vertebrae: $5$
• Sacrum: $5$ fused bones
• Coccyx: $4$ fused bones
• Memorization aid for vertebral counts included above

Cervical Vertebrae

• Atlas, $C1$
• Axis, $C2$
• Cervical vertebrae, $C3$

Comparison of Vertebrae: Thoracic vs Lumbar

• Body:
  • Thoracic: Medium-sized
  • Lumbar: Large
• Superior articular process:
  • Thoracic: Faces posteriorly
  • Lumbar: Faces medially

Sacrum and Coccyx

• Sacrum: $5$ fused bones
• Coccyx: $4$ fused bones
• Anterior view