Unit 2: Skeletal System Lab 2: Axial Skeleton

Unit 2: Skeletal System
Lab 2: Axial Skeleton
Jessica Radke-Snead, RD, MS
Bio 241 Anatomy & Physiology
Bones of the Adult Skeletal System
• Axial skeleton (80)
– LAB 1
• Skull (22)
• Auditory ossicles (6)
• Hyoid bone (1)
– LAB 2
• Vertebral column (26)
• Thoracic cage (25)
• Appendicular skeleton
– LAB 3
Pectoral girdle (4)
Upper limb (60)
Pelvic girdle (2)
Lower limb (60)
Curves of the Vertebral Column
Cervical Vertebrae
• Distinctive features
– All have transverse foramen—protection for the vertebral
arteries—that are NOT present in any other vertebrae
– C1 (atlas) and C2 (axis) allow for head movement  Axis is the
only vertebrae with a dens; begins to form during the first year
of life and fuses with the axis by the age of 3-6 years
– C3-C6 have transverse foramina and bifid spinous processes
– C7 is different—spinous process is not bifid, but especially long
and forms the prominent bump on the lower back of the neck
(vertebra prominens)
• Atlanto-occipital joint: articulation between the atlas and
the cranium
• Atlanto-axial joint: articulation between the atlas and axis
Vertebral Column Bones
Thoracic Vertebrae
• Distinctive features
– Lack transverse foramina and bifid processes
– Spinous processes pointed and angle sharply downward
– Include costal facets  No other vertebrae have ribs articulating
with them
– T1-T10 have transverse costal facets at the end of each transverse
process  provides a second point of articulation for ribs 1-10
– T11 and T12 have NO transverse costal facets  ribs 11 and 12
attach only to the bodies of vertebrae (“floating ribs”)
• Inferior and superior costal facet: position on the vertebrae, not
articulating rib
• Superior and inferior articular facets: position on a vertebrae
– T12 inferior articular facets face laterally instead of anteriorly 
positions them to articulate with the medially facing superior
articular facets of the first lumbar vertebrae
Thoracic vertebrae:
Rib facets: round
fossa where ribs
connect to the
Demifacets: rib facet
divided between 2
Lumbar Vertebrae
• Distinctive features
– Thick, stout body
– Blunt, square-like spinous processes
– Articular processes oriented differently:
• Superior processes face medially
• Inferior processes face laterally (toward the superior
processes of the next vertebrae)  resistant to twisting
Lumbar vertebrae
Rib facets
• Consists of 5 vertebrae  Fuses age 16-26
• Forms the posterior wall of the pelvic cavity
• Consists of 4-5 small vertebrae  Fuses age
• Serves as attachment points for muscles of the
pelvic floor
• Cornua: hornlike projections that serve at
attachment points for ligaments that bind the
coccyx to the sacrum
Thoracic Cage:
Thoracic Cage:
• 12 pairs, no differences between genders
• Attached at posterior (proximal) end to the
vertebral column
• Costal cartilage
– Hyaline cartilage extends from the anterior (distal)
ends of ribs 1-7 to the sternum  “true ribs”
– Ribs 8-10 attach to the costal cartilage of rib 7 – “false
– Ribs 11-12 do not attach to anything at the distal end,
but are embedded in muscle  “false ribs”, “floating
Thoracic Cage:
Thoracic Cage:
Lab 2 Objectives
• Identify and describe the bones and features of the
vertebral column and thoracic bones designated in
your lab
– Observe these structures from multiple viewpoints to
develop a 3D comprehension
• Review the bones and features of the skull (adult and
fetal) designated in lab 1
• Put together a comprehensive understanding of the
axial skeleton
Please be careful with the bones—ask for assistance if
needed! Enjoy!