BACK

Spine Overview

  • Consists of 33 vertebrae with cartilaginous discs in between.

  • Divided into 5 sections:

    • Cervical: 7 vertebrae

    • Thoracic: 12 vertebrae

    • Lumbar: 5 vertebrae

    • Sacral: 5 vertebrae fused together to form the sacrum (fusion occurs in adults, ~16-30 years)

    • Coccygeal: 4 vertebrae fused together to form the coccyx (fusion occurs in adults, ~16-30 years)

Spinal Curvatures

  • Concave (posterior curvature):

    • Thoracic region

    • Sacrococcygeal region

  • Convex (anterior curvature):

    • Cervical region

    • Lumbar region

Functions of the Spine

  • Protects the spinal cord and spinal nerves.

  • Supports the weight of the body superior to the pelvis.

  • Provides a partly rigid and flexible axis for the body and a pivot for the head.

  • Plays an important role in posture and locomotion (keeping the brain over the Center of Gravity).

  • Center of gravity (CoG) or Center of mass (CoM) is affected by factors like:

    • Weight gain/loss

    • Trauma

    • Pregnancy

Abnormal Spinal Curvatures

  • Excessive posterior curvature: Kyphosis

  • Excessive anterior curvature: Lordosis

  • Excessive lateral curvature: Scoliosis

    • More common in athletes involved in unilateral activities (e.g., baseball pitchers) due to muscular development on one side of the trunk.

General Vertebrae Components

  • Spinous process: Where two laminae meet and extend posteriorly; palpable along the midline of the back.

  • Lamina: Connects the pedicles posteriorly, forming flat plates of bone that connect spinous and transverse processes.

  • Pedicle: Connects the transverse processes to the vertebral body.

  • Transverse process: Bony projection located on either side of the vertebrae.

  • Body: Main weight-bearing portion of a vertebra.

  • Vertebral foramen: Opening in each vertebra, forming the vertebral canal when aligned, housing and protecting the spinal cord.

  • Superior and inferior articular processes: Have facets where vertebrae above and below articulate.

    • The inferior articular process of the vertebra above articulates with the superior articular process of the vertebra below.

  • Each vertebra has 7 processes:

    • 1 spinous process

    • 2 transverse processes

    • 2 superior articular processes

    • 2 inferior articular processes

Cervical Vertebrae

  • 7 cervical vertebrae.

  • Atlas (C1):

    • Has no body.

    • Articulates with the skull.

    • No spinous process.

  • Axis (C2):

    • Has a body with a protuberance called the 'dens' or odontoid process.

  • Other Features:

    • Bifid spinous processes.

    • Transverse foramen (small or absent in C7).

    • Triangle-shaped vertebral foramen.

    • Oval-shaped vertebral body.

    • Largest vertebral foramen.

    • Resembles a mole or elephant.

Thoracic Vertebrae

  • 12 thoracic vertebrae.

  • Contain articular facets on their vertebral bodies for the ribs.

  • Spinous and transverse processes are long.

  • Articulation site for ribs (fovea).

  • Circular-shaped vertebral foramen.

  • Heart-shaped vertebral body.

  • Smallest vertebral foramen.

  • Resembles a Giraffe.

  • Ribs attach via articular facets on the vertebral body and transverse processes.

  • Ribs 11 and 12 are floating ribs (not fixed anteriorly).

  • Ribs 8, 9, and 10 are false ribs (connect to the 7th rib by cartilage, then indirectly to the sternum).

Lumbar Vertebrae

  • 5 lumbar vertebrae.

  • Largest vertebrae.

  • Triangle-shaped vertebral foramen.

  • Kidney-shaped vertebral body.

  • Short, sturdy, square spinous process.

  • Short transverse process.

Sacral Vertebrae

  • 5 vertebrae fused together in a triangular-shaped bone (sacrum).

  • Separate at birth and fuse in early adulthood (16-30 years old).

  • Forms a base supporting the weight of the entire body.

Coccygeal Vertebrae

  • 4 vertebrae fused together as a source for muscle and ligament attachments.

  • Fuse during the growth process (~16-30 years).

  • Make up the coccyx.

Intervertebral Discs

  • Cartilaginous discs located on vertebral bodies.

  • Separate vertebrae, allowing nerve roots to pass between them.

  • Act as shock absorbers.

  • Two components:

    • Nucleus pulposus: Soft, gelatinous, elastic tissue in the center of the disc (like the jelly in a donut).

    • Annulus fibrosus: Fibrous tissue forming the outer, more fibrotic part of the disc (like the batter/donut).

Intervertebral Disc Conditions

  • Bulging disc: Annulus fibrosus bulges outward.

  • Herniated disc: Nucleus pulposus protrudes out of the disc due to a tear in the annulus fibrosus.

Ligaments of the Spinal Column

  • Anterior Longitudinal Ligament:

    • Runs along the anterior aspect of the spinal column.

    • Weakest of the spinal column ligaments.

  • Posterior Longitudinal Ligament:

    • Runs along the posterior aspect of the spinal column.

  • Ligamentum Flava:

    • Runs between the laminae of successive vertebrae.

  • Interspinous Ligament:

    • Runs between the spinous processes.

  • Supraspinous Ligament:

    • Runs between the dorsal aspect of spinous processes from the coccyx to C7.

    • From C7 to the external occipital protuberance, it becomes the ligamentum nuchae.

Back Muscles

  • Identify/draw the muscle and describe its action.

  • Do not need to memorize the exact origin, insertion, and nerve innervation.

Extrinsic Back Muscles

  • Produce and control limb and respiratory movements.

  • Superficial:

    • Latissimus Dorsi

    • Trapezius

    • Levator Scapulae

    • Rhomboid Major and Minor
      *Will be reviewed in Module 2 (Upper Limb/Shoulder).

  • Intermediate:

    • Serratus Posterior Superior

    • Serratus Posterior Inferior

Extrinsic Back Muscles: Intermediate

  • Serratus Posterior Superior:

    • Muscle fibers run down and inferiorly.

    • Origin: Spinous processes C7-T3

    • Insertion: Upper ribs

    • Action: Elevation of ribs during respiration

    • Proprioceptive Function

  • Serratus Posterior Inferior:

    • Muscle fibers run superiorly and laterally.

    • Origin: Spinous processes T11-L3

    • Insertion: Lower ribs

    • Innervation: Intercostal nerves (anterior rami)

    • Action: Depression of ribs during respiration

    • Proprioceptive function

  • Proprioception: Perception/awareness of body position and movement.

Intrinsic Back Muscles

  • Produce and control vertebral column movement (centrally located).

  • Maintain posture.

  • Superficial: Splenius muscles (capitis and cervicis)
    *Discussed in Neck Lecture.

  • Intermediate: Erector Spinae Group (3)

  • Deep: Transversospinal Group (3)

  • Deepest: Segmental Group (3)

Intrinsic Back Muscles: Erector Spinae

  • Intermediate.

  • Lie in a 'groove' on each side of the vertebral column between the spinous processes and the angles of the ribs.

  • Chief extensor of the vertebral column.

  • Have a cervical, thoracic, and lumbar section.

  • Iliocostalis (lateral column):

    • Insertion: Transverse processes and angle of the lower ribs.

  • Longissimus (intermediate column):

    • Insertion: Transverse processes and angles of ribs/between tubercles.

  • Spinalis (medial column):

    • Insertion: Spinal processes.

  • Origin (for all three): Broad tendon from the posterior part of the iliac crest, posterior surface of the sacrum, sacroiliac ligaments, sacral and inferior lumbar spinous processes, and supraspinous ligament.

  • Mnemonic: "I Like Standing" (Iliocostalis, Longissimus, Spinalis).

Intrinsic Back Muscles: Transversospinal

  • Semispinalis (Semispinalis capitis, cervicis, dorsi):

    • Origin: Transverse processes of cervical and thoracic vertebrae.

    • Insertion: Spinous process of cervical and thoracic vertebrae (4-6 segments).

    • Innervation: Posterior rami of spinal nerves.

    • Actions:

      • Extension of cervical spine.

      • Lateral flexion/rotation of cervical spine.

      • Stabilization of cervical spine.

    • Does NOT live in the lumbar region.

  • Multifidus:

    • Origin: Transverse processes of all vertebrae.

    • Insertion: Spinous processes of all vertebrae (2-4 segments).

    • Innervation: Posterior rami of spinal nerves.

    • Actions:

      • Extension of vertebral column.

      • Rotation of vertebral column.

      • Stabilization of vertebral column.

  • Rotatores:

    • Origin: Transverse processes of all vertebrae.

    • Insertion: Spinous process of all vertebrae (1-2 segments).

    • Innervation: Posterior rami of spinal nerves.

    • Action:

      • Extension of vertebral column.

      • Lateral flexion/rotation of vertebral column.

      • Stabilization of vertebral column.

      • Proprioception?

Intrinsic Back Muscles: Segmental Group

  • Interspinales:

    • Origin: Spinous Process (SP)

    • Insertion: SP of vertebrae above.

    • Innervation: Posterior rami of spinal nerves.

    • Action: Extension and rotation of the spinal column.

  • Intertransversarii:

    • Origin: Transverse Process (TP)

    • Insertion: TP of vertebrae above.

    • Innervation: Posterior rami of spinal nerves AND anterior rami of spinal nerves.

    • Action: Lateral flexion of the spinal column, extension of spinal column.

  • Levator Costarum:

    • Origin: TP

    • Insertion: Rib between tubercle and angle.

    • Innervation: Posterior rami of spinal nerves.

    • Action: Elevation of ribs in respiration, lateral flexion of spinal column, extension of spinal column.

  • All act to stabilize the vertebral column.

Summary - Osteology

  • Cervical vertebrae

  • Thoracic vertebrae

  • Lumbar vertebrae

  • Sacral/sacrum (depends on age)

  • Coccygeal/coccyx (depends on age)

  • Vertebral column normal:

    • Posterior curvature or concave:

      • Thoracic and sacrococcygeal

    • Anterior curvature or convex:

      • Cervical and Lumbar

    • Functions

  • Vertebral column abnormal:

    • Excessive posterior curvature or concave = Kyphosis

    • Excessive anterior curvature or convex = Lordosis

    • Excessive curvature = Scoliosis

  • Intervertebral Discs

    • Shock absorbers

    • Nucleus pulposus

    • Annulus fibrosus

    • Bulging vs. herniated disc

Summary - Ligaments of the Spinal Column

  • Anterior Longitudinal ligament runs along the anterior aspect of the spinal column

    • Weakest of the spinal column ligaments

  • Posterior Longitudinal ligament runs along the posterior aspect of the spinal column

  • Ligamentum Flava runs between the laminae of successive vertebrae

  • Interspinous ligament runs between the spinous processes

  • Supraspinous ligament runs between the dorsal aspect of spinous processes from the coccyx to C7; C7 to the external occipital protuberance it becomes the ligamentum nuchae

Summary - Muscles

  • Extrinsic Back Muscles (Intermediate)

    • Serratus Posterior Superior

    • Serratus Posterior Inferior
      *Note: Extrinsic superficial (trapezius, latissimus dorsi, Rhomboid major & minor, levator scapulae) muscles will be covered in Module 2

  • Intermediate

    • Erector Spinae Group

      • Iliocostalis

      • Longissimus

      • Spinalis
        *Note: Intrinsic superficial muscles covered in week 1 - Neck (Splenius capitis and cervicis)

  • Deep

    • Transversospinal Group

      • Semispinalis

      • Multifidus

      • Rotatores

  • Deepest

    • Segmental Group

      • Interspinale

      • Intertransverarii

      • Levator Costarum

  • Try to group in terms of muscle actions

    • Respiration

    • Proprioception

    • Extensor of vertebral column

    • Lateral flexion of vertebral column

    • Stabilize vertebral column

    • Lateral rotation of vertebral column