Jessica Radke-Snead, RD, MSBio 241 Anatomy & Physiology

Unit 2: Skeletal SystemLab 2: Axial Skeleton

Review: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 (126)– 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: include:

Rib facets: round fossa where ribs connect to the

vertebrae

or

Demifacets: rib facet divided between 2

vertebraes

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 lack:

Rib facets

and

Transverse foramina

Sacrum• Consists of 5 vertebrae Fuses age 16-26• Forms the posterior wall of the pelvic cavity

Coccyx

• Consists of 4-5 small vertebrae Fuses age 20-30

• 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:Sternum

Thoracic Cage:Ribs

• 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”– Ribs 11-12 do not attach to anything at the distal end,

but are embedded in muscle “false ribs”, “floating ribs”

Thoracic Cage:Ribs

Thoracic Cage:Ribs

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!