Vertebral Column and Muscles of the Back
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- List 5 functions of the vertebral column.
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1. Protects spinal cord and nerves; houses covering of spinal cord.
2. Allows turning motion.
3. Supports upper extremities via indirect connection.
4. Provides scaffolding to help stabilize cavities.
5. Functions in extremity attachment (upper more than lower). - How many vertebrae are in a typical vertebral column? List the types and numbers of each type in superior-inferior order.
- 33 (typically) vertebrae in 5 different groups. Top to bottom: 7 cervical; 12 thoracic; 5 lumbar; 5 sacral (fused to form the sacrum); 3-5 coccygial (fused to form the coccyx).
- What is the vertebra prominens?
- Prominent spinous process of C7, palpable at base of neck.
- Briefly describe the typical vertebra.
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1. BODY: anterior "block" of vertebra.
2. VERTEBRAL ARCH: composed of 2 PEDICLES and 2 LAMINAE. Pedicles connect the body to the laminae.
3. 7 SPINOUS PROCESSES
4. INTERVERTEBRAL DISCS: fibrocartilaginous pads that separate bodies of vertebrae. - List the 7 typical spinous processes.
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1. 1 SPINOUS PROCESS
2. 2 TRANSVERSE PROCESSES
3. 2 INFERIOR ARTICULAR PROCESSES
4. 2 SUPERIOR ARTICULAR PROCESSES - Describe the typical spinous process.
- A median process that projects posteriorly and (usually) inferiorly from the junction of the laminae. Usually overlaps the vertebra below.
- Describe typical transverse processes.
- Project posterolaterally from the junctions of the pedicles and laminae.
- Describe typical articular processes.
- 2 superior and 2 inferior, arising from the juntions of the pedicles and laminae. Each bears an ARTICULAR SURFACE (FACET).
- What is the function of the spinous process?
- Along with transverse processes, afford attachments for deep back muscles and serve as levers for muscles to fix or change position of vertebrae.
- What is the typical function of the transverse processes?
- Along with the spinous process, afford attachments for deep back muscles and serve as levers for muscles to fix or change position of vertebrae.
- What is the function of articular processes?
- Form ZYGAPOPHYSIAL (FACET) JOINTS with adjacent articular processes. E.g., superior articular process of one vertebra articulates with inferior articular process of vertebra directly above it. These joints determine types of movements allowed/restricted in vertebrae. Also assist in maintaining alignment; help prevent vertebra from slipping anteriorly on vertebra below.
- How does curvature of vertebral column change during development?
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1. Embryonic: concave anteriorly.
2. Thoracic convexity pointing anteriorly due to biomechanics of holding head upright (during infancy).
3. Lumbar convexity develops when child begins to stand and walk.
**Cervical and lumbar convexities = secondary curvatures - Define primary and secondary curvature of vertebral column.
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1. PRIMARY: due to vertebrae
2. SECONDARY: due to IV discs; cervical and lumbar IV discs are taller anteriorly - How do IV discs relate to length of the vertebral column? What happens with aging?
- Account for 25% of length. IV disc height lost with age, causing return to anterior concavity (as in fetus).
- List 3 types of pathologic vertebral curvatures.
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1. kyphosis
2. scoliosis
3. lordosis - Define kyphosis.
- Exaggeration of thoracic convexity posteriorly. "Hump" back.
- Define scoliosis.
- Abnormal lateral curvature of vertebral column, accompanied by rotation of vertebrae.
- Identify causes of scoliosis.
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1. MYOPATHIC SCOLIOSIS: Asymmetric weakness of intrinsic back muscles.
2. HEMIVERTEBRA: Failure of half of a vertebra to develop.
3. STATIC SCOLIOSIS: Due pelvic tilt produced by difference in lengths of lower limbs.
4. Due to herniation of IV disc. - Define lordosis.
- Exaggeration of lumbar convexity. Often due to advanced pregnancy or abdominal obesity combined with weak abdominal musculature.
- Define kyphoscoliosis.
- Combination of kyphosis and scoliosis. May severely limit lung inflation.
- Describe thoracic transverse processes and facets.
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1. Transverse processes protrude laterally to attach with ribs.
2. Facets articulate in the coronal plane. - Describe location of scapulae related to thoracic vertebrae.
- Located lateral to spine between 2nd and 7th thoracic vertebrae. Medial edge is palpable landmark for T4.
- What is unique about transverse processes of cervical vertebrae?
- Have TRANSVERSE FORAMINA through which run left and right VERTEBRAL ARTERIES.
- Describe the course of the vertebral arteries through the cervical vertebrae.
- Arise from the first branch of the subclavian artery, course through TRANSVERSE FORAMINA of C6 through C1. Left and right vertebral arteries unite intracranially and provide 1/3 of brain's blood supply.
- What is Tuffier's line?
- Imaginary line that connects the tops of the iliac crests, crosses the L4-L5 junction. Useful for accessing the CSF b/c spinal cord ends at L1-L2.
- Spina bifida
- Neural tube defect marked by congenital cleft of the spinal column, usually with hernial protrusion of the meninges and sometimes the spinal cord.
- Zygapophyseal joint
- = FACET JOINT. Articulation between the SUPERIOR ARTICULAR FACET of one vertebra and the ipsilateral INFERIOR ARTICULAR FACET of the vertebra directly superior.
- Discuss a characteristic of vertebrae that varies with race.
- Spinous processes of cervical vertebrae are often bifid in whites, but not usually so in blacks.
- Spondylolisthesis
- Forward displacement of a vertebra on the one below it, especially of L5 on S1. May produce pain, numbness, tingling of lower extremities/gluteal region due to compression of nerve roots. May be due, e.g., to wearing away of facet joints D/T arthritis, or due to fractured pars interarticularis.
- Pars interarticularis
- Thin slice of bone located between the superior articular facet and the inferior articular facet.
- Describe the junction of sacrum and coccyx.
- Articular surface of the sacrum articulates with the medial aspect of the coccyx.
- Sacral hiatus
- Canal formed by S4 and S5, which are bifid. Needle can be inserted into epidural space for analgesia or to withdraw CSF.
- Interspecies variation in lumbosacral curvature
- Bipedal animals = more curved to offset weight. Humans most curved among primates. Vertical in other animals that are not bipeds.
- Lumbosacral force distribution in humans
- Force is brought down through lumbar vertebrae, dispersed over ala of sacrum, and routed out through the lower extremities.
- Intervertebral foramen
- Not a true foramen b/c formed by 2 bones. Spinal nerves exit here. If stenotic (e.g., d/t herniated disc or disc degeneration), may pinch nerves.
- Anterior longitudinal ligament
- Runs from sacrum to base of skull along anterior surface of vertebral column. Prevents hyperextension.
- Supraspinous ligament
- Runs along the most posterior aspects of the spinous processes. Continues between spinous processes as interspinous ligament.
- Interspinous ligament
- Continuation of the supraspinous ligament between the spinous processes.
- Posterior longitudinal ligament
- Runs along the anterior surface of the vertebral canal, along the posterior borders of the vertebral bodies. Inhibits hyperflexion. Attaches to the skull, where it is called the TECTORIAL MEMBRANE.
- Cruciform and alar ligaments
- Underneath tectorial membrane. Keep C1 and C2 firmly in place. Very important in limiting cervical motion.
- Posterior longitudinal ligament and disc herniation
- PLL inhibits hyperflexion of spine and disc herniation, so that disc herniation usually occurs only posterolaterally. PLL may be injured/severed by seatbelt injury.
- Ligamentum flavum
- Contains high concentration of elastic tissue. Helps restore hyperextended or hyperflexed spine to neutral position. Become POSTERIOR ATLANTO-OCCIPITAL MEMBRANE.
- Innervation of zygapophyseal joints
- Innervated by articular branches that arise from the medial branches of the posterior rami of spinal nerves.
- Nuchal ligament
- Thickened fibroelastic tissue extending from the external occipital protuberance and posterior border of the foramen magnum to the spinous processes of the cervical vertebrae. Provides muscle attachments (C3-C5 spinous processes are short).
- Intervertebral discs
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Comprise 25% of our height. 2 portions:
1. ANNULUS FIBROSIS: outer cartilaginous component; weaker posterolaterally
2. NUCLEUS PULPOSIS: inner gelatinous portion; tends to bulge out through weakened annulus fibrosis, i.e., herniated disc - Batson's plexus
- = INTERNAL VERTEBRAL VENOUS PLEXUS = EPIDURAL VENOUS PLEXUS. Valveless veins that provide pathway from pelvis to brain. Pathway for cancer or infectious agents to spread to vertebral column or even brain. E.g., prostate cancer metastisizes to brain.
- Triangle of Petit
- Bordered by latissimus dorsi, iliac crest, and external abdominal oblique muscles. Weak area where herniation is likely to occur.
- Triangle of auscultation
- Bordered by trapezius, latissimus dorsi, and scapula or rhomboid muscles.
- Native muscles of the back
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Originated in the back (others migrated embryologically).
1. SPLENIUS MUSCLES
2. ERECTOR SPINAE
3. TRANSVERSOSPINALIS - Attachments of muscles of suboccipital triangle
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1. Posterior aspect of C1 (atlas)
2. Spinous process of C2 (axis)
3. Occipital bone