Anatomy: The Spine
Atlantoaxial Joint
"The NO joint" (rotation of the head/shaking head no) formed when the superior articular facets of the axis articulate with the inferior articular facets of the atlas
Atlanooccipital joint
"The YES joint" (flexion and extension/ nodding yes) formed when the superior articular facets of the atlas articulate with the occipital condyles of the occipital bone
The Vertebral body is covered by a thin outer layer of compact bone with spongy bone on the inside
(ignore the arrow pointing to the vertebral foramen)
How many thoracic vertebrae do we have?
12
How many lumbar vertebrae do we have?
5
How many sacral vertebrae?
5 fused vertebrae
The sacrum
5 fused vertebrae
How many cervical vertebrae do we have?
7 C1 is the atlas C2 is the axis
Anything below what part of the sacrum does not bear weight?
Anything below the articular surface of the sacrum is not weight bearing
Lumbar Vertebrae
BODY: thickest of all vertebrae: supports most weight VERTEBRAL FORAMEN: triangular; larger than thoracic, smaller than cervical TRANSVERSE PROCESSES: long and slender with accessory processes on posterior surface that provide attachment for medial intertransverse lumborum muscles (muscles that help with posture) ARTICULAR PROCESSES: superior: directed posteromedially inferior: directed anterolaterally mammillary processes on posterior surface of each sup articular process which provide attachment for multifidis and medial intertransverse muscles SPINOUS PROCESS: short and sturdy; thick, broad, and 'hatchet' shaped
Thoracic vertebrae
BODY: "heart shaped," costal facet for articulation with the head of the rib TRANSVERSE PROCESS: extends posterolaterally T1- T10 have costal facets for tubercle of rib (T 11 and T12 do not because the 11th and 12th ribs are "floating ribs") ARTICULAR PROCESS: sup: directed posteriorly inf: directed anteriorly plane of facets line on arc with center at vertebral body (frontal plane) SPINOUS PROCESSES: long and thin, projects posteroinferiorly (point down) tip extends to level of body of vertebra below
How is the inferior articular process oriented in a cervical vertebrae?
It is located inferioranteriorly (facing the front and facing inferiorally)
How is the superior articular process oriented in a cervical vertebrae?
It is located superiorposteriorly ("up and back")
What is a facet?
It is where the bones articulate
Why is the transverse ligament of the Atlas so important?
It keeps the odontoid process (Dens) of the axis from compressing the spinal cord
The Atlas
No body or spinous process The anterior and posterior arches meet to form a complete ring (can be compared to the lamina of a typical vertebrae) Anterior tubercle can be considered its "body" Posterior tubercle can be considered its "spinous process"
What structure is formed by the inferior articular processes of S5?
Sacral Cornua
Cervical Vertebral Body
Starts at C2 small and wider anteroposteriorly The superior surface is concave with uncinate processes lateral to body The inferior surface is convex
Articular facets
Superior or inferior
What will happen to the size of a vertebral body as the column descends?
The body will increase in size because it will need to hold more weight. The lumbar vertebrae hold more weight than the cervical vertebra, so the body of a lumbar vertebrae is larger.
Which cervical vertebrae has the carotid tubercle and where is it found on that vertebrae?
The carotid tubercle is found on C6 and is located anterior to the transverse foramen.
What does the spinous process of a cervical vertebrae look like and what are the exceptions?
The spinous process of a cervical vertebrae is short and bifid (forked) Exceptions: C1 has no spinous process C7 (vertebra prominens or "the prominent vertrbrea") does not have a bifid spinous process
The Axis
The superior articular facets of the axis articular with the inferior facets of the atlas and allow for rotation of the head (atlantoaxial joint) The dens (odontoid process) is the "body". The dens resides INSIDE the vertebral foramen of C1, anterior to transverse ligament which prevents posterior displacement of the dens which will compress the spinal cord Has a large Bifid process
Base of Sacrum
The superior surface of S1 will articulate with the inferior surface of L5's body The superior articular process of S1 will articulate with the inferior articular facet of L5
Through which cervical vertebrae do the vertebral arteries enter?
The vertebral arteries ascend from the subclavian and enter the transverse foramen at C6 and ascend further. They will not pass through C7.
Why is the vertebral foramen of a thoracic vertebrae smaller than that of cervial and lumbar vertebrae?
There is no thoracic plexus, so the spinal does not enlarge in the thoracic region. Because of this it does not need to be larger.
What do the extrinsic muscles of the back move?
These muscles move the limbs.
What do the intrinsic muscles of the back move?
These muscles move the spine.
What structures do the superior articular facets of the Atlas articulate with?
They articulate with the occipital condyles of the occipital bone to form the atlantooccipital joint..
What do the superior and inferior vertebral notches of two articulating vertebrae form?
They form the intra-vertebral foramen where spinal nerves exit.
Why are the facets of cervical vertebrae arranged nearly horizontally?
This orientation allows for greater range of motion (the rotation and sliding movements used when moving the neck)
Describe the characteristics that can distinguish a cervical vertebrae
Transverse foramen smallest body* greatest range of movement (moving the neck) *C1, the atlas has no body
With the exception of C1, what shape (roughly) is a cervical vertebral foramen?
Triangular
Sacral Canal
a continuation of the vertebral foramen. It contains the cauda equina (horse's tail)
Sacral Foramina
analogous to intervertebral foramina This allows for the exit of posterior and anterior rami of the spinal nerves The anterior foramina is slightly larger than posterior foramina
Vertebral Arch
connected to the vertebral body by the pedicles and come in contact with the spinous process via the laminae
What is the distinguishing characteristic of a thoracic vertebrae?
costal facets for articulation with the ribs
How was the sacral hiatus formed?
formed by absence of laminae and spinous process of S5
What connects and separates the sacral vertebrae in children?
hyaline cartilage connects the sacral vertebrae and intervertebral discs separate them.
What is the costotransverse bar and what does it accomodate?
it is the groove between the ant and post tubercles. It accommodates the anterior rami of cervical spinal nerves
What are the distinguishing characteristics of lumbar vertebrae?
large, thick body (it supports the most weight) short, thick, wide spinous process
Dorsal Surface/ Posterior Surface of Sacrum
median sacral crest- fused spinous processes of S1- S4 intermediate sacral crests- fused articular processes lateral sacral crests- fused transverse processes sacral hiatus leads into sacral canal
Costal facets
on thoracic vertebrae, provide and articular surface for the ribs
Cervical vertebrae Transverse Processes
only vertebrae with transverse foramina which allow vertebral veins, arteries, and sympathetic plexi to pass through has tubercles (anterior and posterior) which allows for the attachment of the levator scapulae and scalene muscles
Apex of the Sacrum
oval facet for articulation with coccyx
Pelvic Surface/ Anterior Surface of the Sacrum
smooth and concave four transverse lines indicate fusion of sacral vertebrae
Auricular Surface of Sacrum
synovial portion of sacroiliac joint (btwn sacrum and ilium)
Vertebral Foramina
the canal through which the spinal cord passes
What sacral landmark is used to divide the abdominal cavit from the pelvic cavity?
the sacral promonotory
What is the sacral promonotory?
the sacral promonotory is the anterior projecting edge of the body of the sacrum
What passes through the transverse foramina of the cervical vertebrae?
vertebral arteries and veins