Axial Skeleton- Vertebral Column

Question 1

What is the vertebral column?

Answer 1

• Composed of 26 bones, including 24 individual vertebrae and the fused vertebrae that form both the sacrum and the coccyx
• Provides vertical support for the body
• Supports the weight of the head
• Helps maintain upright body position
• Helps transfer axial skeletal weight to the appendicular skeleton of the lower limbs
• Houses and protects the delicate spinal cord
• Provides a passageway for spinal nerves that connect to the spinal cord
• Partitioned into 5 regions

Question 2

What are vertebrae?

Answer 2

• Individual bones that are identified by a capital letter that denotes their region, followed by a numerical subscript that indicates their sequence (going from superior to inferior)
• Smallest near the skull and become gradually bigger moving inferiorly through the body trunk as weight bearing increases

Question 3

What are cervical vertebrae?

Answer 3

• There are 7
• Form the bones of the neck
• First cervical vertebrae (C1) articulates superiorly with the occipital condyles of the occipital bone of the skull
• The seventh cervical vertebra (C7) articulates inferiorly with the first thoracic vertebra
• Large foramen

Question 4

What are thoracic vertebrae?

Answer 4

• There are 12
• Form the superior regions of the back and each articulates laterally with one or two pairs of ribs
• The 12th thoracic vertebra (T12) articulates inferiorly with the first lumbar vertebrae
• Lack transverse foramina and bifid spinous processes of the cervical vertebrae
• Have a heart-shaped body that is bigger than those of the cervical vertebra
• Spinous processes tend to angle sharply in an inferior direction

Question 5

What are lumbar vertebrae?

Answer 5

• There are 5
• Form the inferior concave region (“small”) of the back
• The 5th lumbar vertebra (L5) articulates inferiorly with the sacrum
• Largest of all vertebrae, since they bear most of the body’s weight
• Have neither transverse foramina or costal facets
• Thin transverse processes that point dorsolaterally

Question 6

What is the sacrum?

Answer 6

• Formed from 5 sacral vertebrae, which fuse into a single bony structure by the mid to late 20’s
• Articulates with L5 superiorly and with the first coccygeal vertebra inferiorly
• The sacrum also articulates laterally with the 2 ossa coxae (hip bones)
• Forms the posterior wall of the pelvic cavity

Question 7

What is the coccyx?

Answer 7

• Commonly called the “tailbone”
• Formed by 4 coccygeal vertebrae that start to unite during puberty
• The first coccygeal vertebra (Co1) articulates with the inferior end of the sacrum
• When much older the coccyx may also fuse to the sacrum
• Attachment site for several ligaments and some muscles
• The prominent laminae of the first coccygeal vertebrae are known as the coccygeal cornea

Question 8

What are spinal curvatures?

Answer 8

• The vertebral column has some flexibility, so when viewed laterally, the adult vertebral column has 4 curves
• Cervical, thoracic, lumbar and sacral curvatures
• They better support the weight of the body when standing

Question 9

What are the primary spinal curves?

Answer 9

• The thoracic and sacral curvatures
• Appear in late fetal development
• Also called accommodation curves because they accommodate the thoracic and abdominopelvic viscera

Question 10

What are the secondary spinal curves?

Answer 10

• The cervical and lumbar curvatures
• Appear after birth (3-4 months of age)
• These curves arc anteriorly and are also known as compensation curves because they help shift the trunk weight over the legs
• The lumbar curvature appears by the first year of life (learning to stand and walk)

Question 11

What is the vertebral body?

Answer 11

• Cylindrical, anterior region of each vertebra
• Also called a centrum
• The weight-bearing structure of almost all vertebra

Question 12

What is the vertebral arch?

Answer 12

• Posterior to the vertebral body
• Also known as neural arch
• Together the vertebral body and arch enclose a roughly circular opening called the vertebral foramen
• Composed of 2 pedicles and 2 laminae

Question 13

What is the vertebral canal?

Answer 13

• Collectively all the stacked vertebral foramina form a superior-to-inferior directed canal that contains the spinal cord

Question 14

What are intervertebral foramina?

Answer 14

• Lateral openings between adjacent vertebrae

- Provide a horizontally directed passageway through which spinal nerves travel to other parts of the body

Question 15

What are vertebral pedicles?

Answer 15

• Originate from the posterolateral margins of the body (foot)
• 2 parts make up a section of the vertebral arch

Question 16

What are vertebral laminae?

Answer 16

• Extend posteromedially from the posterior edge of each pedicle
• 2 parts make up a section of the vertebral arch

Question 17

What are spinous processes?

Answer 17

• Project posteriorly from the left and right laminae (middle of the arch)
• Most can be palpated through the skin of the back

Question 18

What are transverse processes?

Answer 18

• Lateral projections on both sides of the vertebral arch

Question 19

What are articular processes?

Answer 19

• On both the superior and inferior surfaces of each vertebra
• Project from the junction between the pedicles and laminae
• The inferior articular processes of each vertebrae articulate with the superior articular processes of the vertebra immediately inferior to it
• Each have a smooth surface called an articular facet (angles of these differ)

Question 20

What are intervertebral discs?

Answer 20

• Pads of fibrocartilage that separate adjacent vertebral bodies
• Make up about one quarter of the entire vertebral column
• Act as shock absorbers and allow the vertebral column to bend (can withstand a certain amount of compression)
• Composed of an outer ring of fibrocartilage called the annulus fibrosus
• And an inner circular region called the nucleus pulposus

Question 21

What are transverse foramina? (cervical vertebrae)

Answer 21

• The transverse processes of the first 6 cervical vertebrae are unique in that they contain prominent round foramen
• Provide a protective bony passageway for the vertebral arteries and veins supplying the brain

Question 22

What is the atlas? (cervical vertebrae)

Answer 22

• The first cervical vertebra (C1)
• Supports the head via its articulation with the occipital condyles of the occipital bone
• It’s recognizable from other vertebrae because it lacks a body and a spinous process
• Has lateral masses that are connected by semicircular anterior and posterior arches
• Each arch containing anterior and posterior tubercles
• Atlas has depressed oval superior articular facets that articulate with the occipital condyles

Question 23

What is the axis? (cervical vertebrae)

Answer 23

• During development, the body of the atlas fuses to the body of the second cervical vertebra (C2)
• This fusion produces the dens

Question 24

What is the dens? (cervical vertebrae)

Answer 24

• The most distinctive feature of the axis
• Rests in the articular facet for dens of the atlas, where it is held in place by a transverse ligament
• Acts as a pivot for the rotation of both the atlas and the skull
• Because both the dens and the spinal cord occupy the vertebral foramen at the level of the axis, any trauma that dislocates the dens often results in serious injury

Question 25

What is the atlanto-occipital joint? (cervical vertebrae)

Answer 25

• The articulation between the occipital condyles and the atlas
• Permits us to nod our head “yes”

Question 26

What is the atlantoaxial joint? (cervical vertebrae)

Answer 26

• The articulation between the atlas and the axis

- Permits us to shake our heads “no”

Question 27

What is the vertebra prominens? (cervical vertebrae)

Answer 27

• The seventh cervical vertebra (C7)
• Represents a transition to the thoracic vertebral region and has some features of thoracic vertebrae
• Has a large spinous process which can be easily felt through the skin (slight protrusion between the shoulder blades and inferior to neck

Question 28

What are costal facets/ demifacets? (thoracic vertebrae)

Answer 28

• On the lateral side of the body and on the sides of the transverse processes
• Costal facets: circular depression that articulates with the entire head of the rib
• Costal demifacets: semicircular depression that articulates with either the superior or inferior edge of the head of the rib

Question 29

Vertebra T1-T10 have… (facet variations/thoracic vertebrae)

Answer 29

• Transverse costal facets on their transverse processes

Question 30

Vertebrae T11-T12 lack… (facet variations/thoracic vertebrae)

Answer 30

• Transverse costal facets, because the 11th and 12th ribs do not have tubercles

Question 31

What are the variations found in the bodies of the thoracic vertebrae?

Answer 31

• Body of T1 bears a full costal facet for the first rib and a demifacet for the second rib
• The bodies of the vertebrae T2-T8 have 2 demifacets each
• The body of the vertebrae T10-T12 have a single whole facet to articulate with the respective ribs

Question 32

What is the apex of the sacrum?

Answer 32

• A narrow, pointed portion of the bone that projects inferiorly

Question 33

What is the sacral canal?

Answer 33

• The vertebral canal of the sacrum that becomes much narrower
• Terminates in an inferior opening called the sacral hiatus (represents where the laminae of the last sacral vertebrae failed to fuse)

Question 34

What is the promontory? (sacrum)

Answer 34

• The anterosuperior edge of the first sacral vertebrae which bulges anteriorly into the pelvic cavity

Question 35

What are sacral foramina? (sacrum)

Answer 35

• Paired anterior sacral foramina permit the passage of nerves to the pelvic organs
• On the dorsal side of the sacrum there are paired posterior sacral foramina that are openings for spinal nerves

Question 36

What is the auricular surface? (sacrum)

Answer 36

• On the lateral surface of the sacrum wings (ala)

- Marks the site of articulation with the os coxae of the pelvic girdle forming the sacroiliac joint