Spine Anatomy/Physiology Flashcards
Vertebral Column
33 total vertebrae
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 3-4 coccyx
Function: support trunk & protect spinal cord
Spinal Nerves
- C1 above C1 vertebra
- C8 between C7/T1
- Thoracic & lumbar nerves below their respective vertebra (L5 nerve exits at L5/S1 interface)
Spinal Curves
Function: Allow greater load bearing
4 Curves:
- Cervical Lordosis: convex anteriorly b/t C1 & T2
- Thoracic Kyphosis: concave anteriorly b/t T2 & T12
- Lumbar Lordosis: convex anteriorly b/t T12 & sacral joints
- Sacral Kyphosis: concave anteriorly b/t lumbosacral joint & tip of the coccyx
- Kyphoses = primary curves; present at birth
- Lordosis = secondary curves; develop w/ development of erect posture
Vertebral Columns
Anterior: Vertebral body
- Sustains compressive loads
- Increases in mass & area from cervical to lumbar regions
Middle: Pedicles
- Transfers forces b/t anterior & posterior columns
Posterior:
- Laminae, articular processes, & spinous/transverse processes
- Provide area for muscle attachment & help regulate movement
Articular Processes of Vertebrae
Cervical: point inferiorly & anteriorly (up & down) – flexion & extension
Thoracic: point posteriorly & superiorly (front & back) – rotation
Lumbar: point laterally (side to side) – flexion & extension
Vertebral Components
- Vertebral body–anterior; supports body weight
- Vertebral arch–posterior; encloses the vertebral foramen to protect the spinal cord; consists of 2 rounded pedicles & 2 flat laminae that unite posteriorly in midline
- 3 processes (2 transverse, 1 spinous); provide muscle attachments
- 4 articular processes (2 superior, 2 inferior); junction = articular facet (zygapophyseal joint) w/ a capsule & articular cartilage
Cervical Vertebrae
- Transverse processes contain a foramen transversarium (except C7), which vertebral arteries pass through*
- Small & wide vertebral body
- Large & triangular vertebral foramen
Atlas
C1 vertebra:
- body replaced by an anterior arch
- function: support head w/ 2 prominent articular facets to balance occipital condyles (allows for free flexion)
Axis
C2 vertebra: dens, odontoid process
- articulates w/ anterior arch of C1
- held in place by ligaments, allowing it to be a pivot that the atlas rotates around
Odontoid Fractures
-Type 1 (left)–mechanically stable; avulsion fracture of the alar ligaments
Type 2 (center)–MC & worst prognosis; instability & non-union are possible; located at base of odontoid
Type 3 (right)–favorable prognosis if reduced; fracture through the cancellous bone of the vertebral body
Thoracic Vertebrae
- 2 hemifacets (superior & inferior costal facets) on each body, which attach to rib heads
- 1 facet (transverse costal facet) on each transverse process for attachment of rib tubercle
Thoracic Vertebrae: “Rule of 3’s”
Describes the relationship b/t the spinous processes & thoracic vertebral bodies
- T1-3: spinous processes project at the same level as the attached vertebral body
- T4-6: spinous process project 1/2 vertebra below the attached vertebra
- T7-9: spinous process located 1 full vertebra below the attached vertebra
- T10-12: spinous processes return to the same level as the attached vertebral body
Sacrum
5 fused sacral vertebrae –> single bone
Sacral Hiatus:
- caudal end of the sacrum
- laminae of 5th sacral vertebrae are not fused, leaving an inferior opening (epidural space NOT near the dura mater)
- used in anesthesia & analgesia
Spinal Surface Anatomy
C0 = external occipital protuberance C1 = atlas transverse process below mastoid process C2 = 1st bony prominence below occiput C3 = level of the hyoid bone C4-5 = level of the thyroid cartilage C6 = level of cricoid ring C7 = spinous process does not move w/ extension T2 = superior angle of the scapula T3 = scapular spine T7 = inferior angle of the scapula T12 = inferior rib margin
Superficial Back Muscles
Trapezius Latissimus dorsi Levator scapulae Rhomboid major Rhomboid minor
Trapezius
Origin: (1) external occipital protuberance (2) ligament nuchae (3) spinous process of C7-T12
Insertion: (1) lateral 1/3 of clavicle (2) acromion (3) spine of scapula
Innervation: spinal accessory nerve (CN 11)
Action: scapular movement
- Superior fibers–elevation & upward rotation
- Middle fibers–retraction
- Inferior fibers–depression & upward rotation
Latissimus Dorsi
Origin: (1) spinous processes of T7-T12 (2) thoracolumbar fascia (3) iliac crest
Insertion: bicipital groove of humerus
Innervation: thoracodorsal nerve
Action:
- adduct, extend, & internally rotate the humerus
- scapular depression & protraction