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
Levator Scapulae
Origin: transverse processes of C1-C4
Insertion: superior part of the medial border of the scapula
Innervation: dorsal scapular nerve
Action: elevation & downward rotation of the scapula
Rhomboid Major/Minor
Origin:
- Major: spinous process of T2-T5
- Minor: (1) ligamentum nuchae (2) spinous processes of C7-T11
Insertion: vertebral border of the scapula
Innervation: dorsal scapular nerve
Action: retraction & downward rotation of the scapula
Suboccipital Muscles
Rectus capitus posterior major
Rectus capitus posterior minor
Obliquus capitus inferior
Obliquus capitus superior
Rectus Capitus Posterior Major Muscle
Attach:
- spinous process of C2 –> occipital bone
Action:
- extension of the head and neck
Innervation:
- C1 dorsal rami (suboccipital nerve)
Rectus Capitus Posterior Minor Muscle
Attach:
- posterior tubercle of C1 –> occipital bone
Action:
- extension of the head & neck
Innervation:
- C1 dorsal rami (suboccipital nerve)
Obliquus Capitus Inferior Muscle
Attach:
- spinous process of C2 –> transverse process of C1
Action:
- ipsilateral extension & rotation of the head
Innervation:
- C1 dorsal rami (suboccipital nerve)
Obliquus Capitus Superior Muscle
Attach:
- transverse process of C1 –> occipital bone
Action:
- ipsilateral extension & lateral flexion of the head
Innervation:
- C1 dorsal rami (suboccipital nerve)
Intermediate Back Muscles
Serratus posterior superior
Serratus posterior inferior
Serratus Posterior Superior
Origin: (1) ligament nuchae (2) spinous process of C7-T2/3
Insertion: superior border of ribs 2-5
Innervation: ventral rami (T1-5)
Action: forced inspiration (by elevation of the ribs)
Serratus Posterior Inferior
Origin: (1) spinous process of T11-L2/3 (2) thoracolumbar fascia
Insertion: inferior borders of ribs T9-T12
Innervation: ventral rami (T9-T12)
Action: forced expiration (by depression of the ribs)
Deep Lateral Back Muscles
Splenius capitus
Splenius Cervicis
Action:
- Extension of the head & cervical spine w/ bilateral contraction
- Ipsilateral flexion of the head & cervical spine w/ unilateral contraction
Splenius Capitis Muscle
Origin:
- Ligamen nuchae
- Spinous processes of C7-T3
Insertion: Lateral occipital bone
Innervation: Dorsal primary rami (C3-C5)
Splenius Cervicis
Origin: Spinous processes of T3-T6
Insertion: Transverse processes of C1-C3
Innervation: Dorsal primary rami (C5-C7)
Erector Spinae Muscle
Deep Parallel Group
- Spinalis (thoracis, cervicis, capitus)
- -attaches spinous processes from the semispinalis capitis superiorly to L1-2 - Longissimus (thoracis, cervicis, capitus)
- -attaches transverse processes from the mastoid process superiorly to the thoracolumbar fascia inferiorly - Illiocostalis (lumborum, thoracis, cervicis)
- -attaches ribs from the transverse processes of C4-C6 superiorly to the iliac crest inferiorly
Action: Extension of the spine
Innervation: Dorsal rami
Transversospinalis Muslce
Deep Medial Group
- Semispinalis (thoracis, cervicis, capitus)
- Attach: posterior occiput/cervical spinous process to distal transverse processes
- Action: extend & rotate spine to opposite side - Multifidi (lumborum, thoracis, cervicis)
- Attach: runs in groove b/t transverse & spinous processes from C2 to the sacrum
- Action: extend, laterally flex, & rotate spine - Rotatores (lumborum, thoracis, cervicis)
- Attach: laminae superiorly to the transverse process of the inferior vertebra
- Action: rotation b/t adjacent vertebrae
Innervation: Dorsal rami
Deep Intersegmental Muscle Group
- Interspinalis
- Attach: spinous processes
- Action: extension of spine - Intertransversarii
- Attach: transverse processes
- Action: lateral bending of spine - Levatores Costarum
- Attach: ribs to transverse process of C7-C11
- Action: elevation of ribcage
Innervation: Dorsal Rami
Spine Ligaments
- Composed primarily of collagen–allow minimal elongation
- Highly innervated & pain sensitive
Function:
- Provide intrinsic stability
- Transfer tensile loads from one vertebrae to another to facilitate motion & prevent sudden forces
Supraspinous Ligament
Across tips of spinous processes
- does not exist below L3
- Limit flexion (thus, can be injured w/ forced flexion)
Interspinous Ligament
Runs b/t spinous processes C7-L3
- Limit flexion (thus, can be injured w/ forced flexion)
Ligament Flavum
Paired ligaments connecting adjacent laminae
- No afferent pain innervation
- Limit flexion (thus, can be injured w/ forced flexion)
Anterior Longitudinal Ligament
- Runs along the anterior aspect of the vertebral body from the occiput to the sacrum
- Narrower superiorly & broader inferiorly
- Limits extension of the spine (thus, can be injured w/ forced extension, spondylolisthesis, or fractures/dislocations of the vertebrae
Posterior Longitudeinal Ligament
- Runs along the posterior aspect of the vertebral body from C2 to the sacrum
- Broad in the cervical region, hourglass in the thoracic region & tapers in the lumbar region
- Covers only 50% of the vertebral body
- Limits flexion of the spine (thus, can be injured w/ forced flexion or w/ fractures/dislocations of the vertebrae
Thoracolumbar Fascia
- 3 layers: anterior, middle, posterior
- Connects muscles (latissimus dorsi, transversus abdominis, internal obliques, gluteus maximus), ligaments, & bones to allow for coordinated movements of the spine
- Kinetic chain–humerus is connected to the contralateral femur
Intervertebral Disc
Components:
- inner nucleus pulposus (water & mucoprotein gel in a network of type II collagen)
- outer annulus fibrosus (15-20 laminae composed of type I collagen in an oblique layering)–increases tensile strength (posterolaterally-less organized, less strong)
- end plates (cartilage)
Nucleus pulposus contents retain fluid, which decreases w/ age & becomes replaced by amorphous fibrocartilage, which changes the mechanical behavior
Lumbar Disc Herniation
MC = Posterolateral herniation
- Posterolateral protrusion at L4/5 disc affects L5 nerve
- Posterolateral protrusion at L5/S1 disc affects S1 nerve
3-Joint Complex
Disc + 2 facet joints
Kirkaldy-Willis Degenerative Cascase
- pathology of 1 joint affects the others
- begins w/ years of rotation & flexion –> cumulative compressive strain & microtrauma
- degeneration of the spine (= spondylosis)
