Overview
This lecture reviews the axial skeleton, including its structure, bone types, and distinguishing features. Emphasis is given to bone classification, major bone groups, and identifying different vertebrae.
Skeletal System Overview
- The skeleton is divided into the axial (80 bones) and appendicular (126 bones) skeletons.
- Functions include body support, movement, organ protection, mineral storage, and blood cell production.
Bone Classification & Anatomy
- Bones are classified as short, irregular, long, and flat.
- Bone markings are projections (for muscle/ligament attachment or joint formation) or depressions/openings (for nerves and blood vessels).
- Long bones feature proximal/distal epiphyses (compact bone) and a diaphysis with yellow bone marrow in the medullary cavity.
- Flat bones have compact bone outside and spongy bone inside.
Axial Skeleton Components
- Includes the cranium, facial bones, associated bones (e.g., hyoid), thoracic cage, and vertebral column.
- Cranium: 8 bones; face: 14 bones; 7 associated bones.
Cranial and Facial Bones
- Cranial bones: frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
- Facial bones include vomer, zygomatic, nasal, inferior nasal concha, palatine, maxilla, mandible, and lacrimal bones.
Foramina & Cranial Nerves
- Foramina are bone openings for cranial nerves and blood vessels.
- Each cranial nerve (I–XII) passes through specific foramina, generally from front to back.
- Mnemonics can help memorize cranial nerve order and their foramina.
Thoracic Cage
- Composed of the sternum (manubrium, body, xiphoid process) and 12 ribs.
- True ribs (1–7) attach directly to the sternum; false ribs (8–12) do not; floating ribs (11–12) are a subset of false ribs and attach to neither sternum nor cartilage.
Vertebral Column
- Regions: cervical (7 vertebrae), thoracic (12), lumbar (5), sacrum (5 fused), coccyx (4 fused).
- Cervical vertebrae: atlas (C1), axis (C2, with dens), and typical cervical vertebrae distinguishable by structure.
- Thoracic vertebrae: medium body, superior articular facets face forward ("giraffe" profile).
- Lumbar vertebrae: large body, superior facets face inward ("moose" profile).
- Sacrum and coccyx are easily identifiable as fused bone groups.
Key Terms & Definitions
- Axial Skeleton — consists of the skull, vertebral column, and thoracic cage.
- Appendicular Skeleton — consists of limb bones and girdles.
- Projection — bone marking where muscles, tendons, or ligaments attach or joints form.
- Depression/Opening — bone marking allowing passage of nerves/blood vessels.
- Foramen — hole or opening in bone for nerves/vessels.
- Epiphysis — ends of a long bone.
- Diaphysis — shaft of a long bone.
- Compact Bone — dense outer layer of bone.
- Spongy Bone — porous bone inside, contains marrow.
Action Items / Next Steps
- Memorize the names and locations of cranial and facial bones.
- Learn the order and foramina of cranial nerves using mnemonics.
- Identify key differences between cervical, thoracic, and lumbar vertebrae.
- Prepare for next week's lab on the appendicular skeleton.