axial

• Divisions of the Skeleton

  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  • Bones of head and trunk
  • Forms longitudinal axis of body
• Axial skeleton has 80 bones
• Components of the Axial Skeleton

  • Skull
  • Bones associated with the skull
  • Thoracic cage
  • Vertebral column
• Skull


  • 8 cranial bones
  • 14 facial bones
• Bones associated with the skull

  • 6 auditory ossicles
  • hyoid bone
• Thoracic cage


  • Sternum
  • 24 ribs
• Vertebral column


  • 24 vertebrae
  • sacrum
  • coccyx
• Functions of the axial skeleton

  • Supports and protects organs in body cavities
  • Provides points of attachment for muscles
• Muscle functions related to axial skeleton

  • Adjust positions of head, neck, and trunk
  • Perform breathing movements
  • Stabilize parts of appendicular skeleton
• The skull contains 22 bones
• Cranial bones


  • 8 cranial bones
  • 14 facial bones
• Cranial bones


  • Enclose cranial cavity, containing the brain
  • Protect and support entrances to digestive and respiratory tracts
• Auditory ossicles


  • Three tiny bones in tympanic cavity
  • Transfer sound vibrations from tympanic membrane to internal ear
• Hyoid bone


  • Supports the larynx
  • Attaches muscles of larynx, pharynx, and tongue
  • Serves as a moveable base for the tongue
  • The only bone that does not articulate with another bone
• Vertebral column


  • Protects the spinal cord
  • Supports the head and body
  • Consists of 26 bones
• Spinal curves


  • Cervical curve
  • Thoracic curve
  • Lumbar curve
  • Sacral curve
• Thoracic and sacral curves


  • Called primary curves
  • Present during fetal development
  • Accommodate internal organs
• Cervical and lumbar curves

  • Called secondary curves
  • Appear after birth
  • Shift body weight to permit upright posture
• Five Vertebral Regions


  • Cervical
  • Thoracic
  • Lumbar
  • Sacral
  • Coccygeal
• Vertebrae in Neck


  • Seven cervical vertebrae
• Vertebrae in Upper back

  • 12 thoracic vertebrae
• Vertebrae in Lower back

  • Five lumbar vertebrae
• Vertebral anatomy


  • Vertebral body
  • Vertebral arch
  • Articular processes
• Vertebrae are numbered by region, from top to bottom
• C1 articulates with skull, L5 with sacrum
• Vertebrae of each region


  • Have characteristics determined by functions
• Regions of the vertebral column

  • Cervical (C)
  • Thoracic (T)
  • Lumbar (L)
  • Sacral (S)
  • Coccygeal (Co)
• Cervical vertebrae


  • C1 to C7
  • Small body
  • Large vertebral foramen
  • Concave superior surface
  • Anterior edge is inferior to posterior edge
• Thoracic vertebrae


  • T1–T12
  • Heart-shaped bodies
  • Larger bodies
  • Smaller vertebral foramina
  • Long, slender spinous process
  • Dorsolateral surfaces have costal facets
• Lumbar vertebrae


  • L1–L5
  • Largest vertebrae
  • Thick, oval-shaped bodies
  • No costal facets
  • Triangular vertebral foramen
  • Superior articular processes face medially
  • Inferior articular processes face laterally
  • Slender transverse processes project dorsolaterally
  • Massive spinous processes
• Sacrum and coccyx


  • L5 articulates with the sacrum
  • Sacrum articulates with the coccyx
• Sacrum


  • Curved, more so in males than in females
  • Protects reproductive, urinary, and digestive organs
  • Attaches axial skeleton to pelvic girdle
  • Attaches broad muscles that move the thigh
• The adult sacrum consists of five fused sacral vertebrae
• Fusion of sacral vertebrae occurs between puberty and ages 25–30
• Leaving transverse lines
• Mature coccyx consists of three to five fused coccygeal vertebrae
• Coccyx


  • Attaches ligaments and a constricting muscle of the anus
• Thoracic cage


  • Skeleton of the chest
  • Thoracic vertebrae
  • Ribs
  • Costal cartilages
  • Sternum
• Functions of thoracic cage

  • Protects organs of the thoracic cavity
  • Provides attachment for muscles involved in breathing