DEEP BACK - VERTEBRAL COLUMN - SPINAL CORD
I. DEEP BACK MUSCLES
- intrinsic muscles
A. Concerned with maintenance of posture and movements of vertebral column and head
B. Superficial layer of deep back muscles
- innervated by dorsal primary rami - deep to trapezius and rhomboids – spinotransverse – run up and out
1. Splenius muscles (capitis and cervicis)
a. Attachments: ligamentum nuchae and spines of T1-6 to mastoid process and superior nuchal line (capitis) and transverse processes of C1-4 (cervicis)
b. Nerve: cervical nerves (dorsal rami)
c. Action: flex and rotate the head and neck to same side
C. Intermediate layer of deep back muscles
- ERECTOR SPINAE MUSCLES - arranged in 3 columns, common origin (sacrospinalis) –
(Mnemonic I Like Standing for iliocostalis, longissimus, spinalis) – run parallel to vertebral column
1. Iliocostalis lumborum, thoracis, cervicis- lateral groups
a. Attachments: iliac crest, sacral and lumbar spines processes to ribs
b. Nerve: spinal nerves (dorsal rami)
c. Action: extend and bend vertebral column
2. Longissimus thoracis, cervicis, capitis - intermediate column
a. Attachments: transverse processes lower to transverse processes upper, mastoid process
b. Nerve: spinal nerves
c. Action: extend vertebral column
3. Spinalis thoracis, cervicis, capitis- medialmost – poorly developed
a. Attachments: spinous process to spinous process
b. Nerve: spinal nerves
c. Action: extend vertebral column
D. Tranversospinal group of muscles
- deep to erector spinae - from transverse processes to spinous processes - innervated by dorsal rami – lie in groove between SP and TP
1. Semispinalis thoracis, cervicis, capitis
a. Action: extend upper vertebral column and rotate it toward opposite side
2. Multifidus - heaviest in lumbar region – pass over 2-3 vertebrae
a. Action: extend vertebral column
3. Rotatores - shortest, cross one to two vertebrae
E. Minor deep back muscles - elevate ribs - laterally bend vertebral column - innervated by dorsal primary rami of spinal nerves
1. Interspinalis - between adjacent spinous processes at cervical and lumbar levels
2. Intertransversarii - connect adjacent transverse processes at cervical and lumbar levels
3. Levatores costorum - between transverse processes and ribs below - respiratory
II. SUBOCCIPITAL REGION
A. Suboccipital muscles - components of transversospinal muscle group - deep to semispinalis capitis - postural muscles - all innervated by C1 (dorsal rami)
B. Suboccipital Triangle
1. borders:
a. area between the two oblique muscles and rectus capitis major muscle
b. floor - atlanto-occipital membrane
c. roof - semispinalis capitis muscle
2. contents:
a. vertebral artery
b. suboccipital nerve (dorsal ramus of C1) to muscle to triangle
c. greater occipital nerve (dorsal ramus of C2) - courses across triangle
d. occipital artery - accompanies greater occipital nerve on scalp
III. VERTEBRAL COLUMN
A. Primary and secondary curvatures
1. Thoracic and sacral are PRIMARY
2. Cervical and lumbar are SECONDARY
3. Thorax and sacral are permanent
4. Lumbar curvature is more pronounced in males
B. Functions
1. Posture
2. Weight support
3. Locomotion
4. Protects spinal cord and nerve roots
C. Abnormalities
1. Kyphosis – “humpback” - convex posteriorly - thoracic-(common)
2. Scoliosis - lateral curvature - most common type of vertebral column defect
3. Lordosis - "swayback" - anterior convexity – associated with pregnancy or obesity
D. Palpation
1. C7 - vertebra prominens
2. Thoracic easily palpable
3. Sacral triangle
4. Sacral hiatus
E. Parts of typical vertebrae
1. Body - large anterior part-nutrient foramen anteriorly
a. support weight
b. at T4 gets larger
2. Vertebral arch - encloses vertebral foramen
a. protects cord and nerve roots
b. pedicles (2) - contain vertebral notches >> intervertebral foramen
c. lamina (2) - form roof of vertebral foramen - overlap
d. spinous process
3. Vertebral processes
a. spinous (1)
b. transverse (2)
c. articular - facets (4)-superior and inferior
F. Regional characteristics of vertebrae
1. Cervical (7)
a. large foramen (transervarium) in each transverse process (passage of vertebral artery and vein)
b. short, bifid spinous processes - C3-6
c. atlas - 1st cervical vertebrae
1. no spinous process
2. large vertebral foramen
3. anterior and posterior arch
4. prominent superior articular surface - support skull
5. Ant. & post. tubercle
d. axis - 2nd cervical vertebrae-strongest
1. dens (odontoid process)- pivot for atlas
2. bifurcated spinous processes
2. Thoracic (12)
a. heart-shaped bodies, two costal facets for ribs (1-10)
b. spinous processes long and point downward
c. transverse process are thick and long
3. Lumbar (5)
a. large bodies - no costal facets
b. spinous processes thick, hatchet-shaped
c. mammillary process
d. Clinical anomalies of lumbar vertebrae
4. Sacral (5)
a. fusion of 5 vertebrae
b. large sacral foramina for passage of ventral rami of sacral nerves
c. median sacral crest - reduced spinous process
d. Sacral hiatus-no lamina or spinous processes
i. anesthesia
ii. filum terminale
iii. S5 nerve
iv. coccygeal nerve
5. Coccygeal (4)
- Remnant of tail
G. Joints of the vertebral column -
1. Joints of vertebral bodies - 25% of total length
a. Intervertebral discs - plates of fibrocartilage-weight bearing
i. anulus fibrosis - fibrocartilage - concentric rings(change with age)
ii. nucleus pulposis - gelatinous - elastic - avascular(change with age)
iii. most superior C2-3, inferior L1-S5
b. Anterior longitudinal ligament - fixed to discs and periosteum - prevents hyperextension ("whiplash")– connects vertebral bodies with disk -anterior to vertebral body
c. Posterior longitudinal ligament - within vertebral canal - attaches to discs -prevents hyperflexion - posterior to vertebral body
2. Joints of vertebral arches (zygapophyseal joints) - united by synovial joints
3. Accessory ligaments
a. ligamenta flava - elastic ligaments, connect adjacent laminae anteriorly
b. interspinous and supraspinous
c. ligamentum nuchae (superior interspinous ligament)- triangular extension of supraspinal ligament, connects to external occipital protuberance and medial nuchal line of occipital bone
d. intertransverse
H. Craniovertebral joints - discussed later
I. Blood vessels of vertebral column
1. Spinal arteries
a. postcentral branch
b. prelaminar branch
c. radicular branches - follow nerve rootlets - supply spinal cord
2. Veins
a. internal vertebral plexus - between dura and spinal canal
b. external vertebral plexus - communicate with internal plexus
c. vertebral veins
d. valveless
IV. SPINAL CORD AND ITS COVERINGS
A. Located in vertebral canal (neural canal) - occupies superior 2/3 of vertebral canal
B. Continuation of medulla (oblongata)
C. Extends from foramen magnum to L2
D. Cervical enlargement - C4-T1 - innervation of upper limb - brachial plexus
E. Lumbosacral enlargement - L2-S3 - innervation of lower limb - lumbar and sacral plexus
F. Spinal cord segments do not correspond to vertebral levels
G. Age differences
1. Embryonic - extends entire length
2. Newborn - L2-3 termination
3. Adult - L1 termination
H. Coverings = meninges]
1. Epidural (extradural) space
a. fat
b. connective tissue
c. venous plexus - anterior and posterior internal vertebral plexus
d. spinal arteries - in subarachnoid space
2. Dura mater
a. terminates as coccygeal ligament
b. denticulate ligaments - suspension of pia mater - 21 attachments
c. blends with epineurium of spinal nerves
d. subdural space - potential space
3. Arachnoid
a. subarachnoid space - contains cerebrospinal fluid (CSF)
b. arachnoid trabeculae – connect to pia mater
4. Pia mater
a. continues as filum terminale - intradural portion ends at S2
b. denticulate ligaments –
anchor cord via attachments to the inner surface of the dural sac (i.e. connect the pia and dura mater sheaths)
5. Subarachnoid space
a. formed by choroid plexus
b. lumbar cistern L2-S2
c. shock absorbtion
d. Spinal tap = lumbar puncture – at L4-5 interspace
I. Spinal cord
1. 31 pairs of spinal nerves - C1 above C1 vertebrae, C8 below C7 vertebrae
2. dorsal horn - receives sensory information
3. ventral horn - motor innervation
4. intermediolateral cell column
a. autonomic cell bodies (preganglionic)
b. present T1-L2
c. sympathetic portion of autonomic nervous system
5. Dorsal root
a. afferent sensory fibers
b. spinal ganglia = dorsal root ganglion (DRG)
6. Ventral root
a. motor fibers
7. Spinal nerve (mostly somatic)
a. emerge through intervertebral foramina
b. cauda equina - elongate dorsal and ventral rootlets in subarachnoid space - caudal to termination of spinal cord
c. Components
i. GSA – mostly cutaneous
ii. GSE – to skeletal muscles
iii. GVA- from viscera
iv. GVE - autonomics
8. conus medullaris - inferior end of spinal cord - continues as filum terminale @ L2
J. Blood supply to spinal cord
1. Arteries
a. anterior spinal artery - from vertebral a., supplies anterior 2/3 of spinal cord
b. posterior spinal arteries (2), supply posterior 1/3 of spinal cord - from vertebral a.
c. radicular arteries - enter vertebral canal and divide into anterior and posterior radicular arteries, supply meninges - from various sources
d. great anterior radicular artery (of Adamkiewicz) - larger - supplies inferior 2/3 thoracic, superior lumbar and lumbosacral enlargement - mostly from the left inferior intercostal a.
2. Veins
a. distribution similar to arteries
b. 3 anterior and 3 posterior spinal sinuses (veins)
c. internal vertebral plexus
d. continuous with venous plexi in skull, thorax and abdomen
e. route for spread of metastases or infections