Back

toc =Back=

Dr. Hankin 5 Nov 2007 @ 9 AM

Objectives

 * 1) **Define the movements of the back and its skeletal elements.**
 * 2) **Define the normal and basic pathological spinal (postural) curvatures.**
 * 3) **Describe a typical vertebra and the characteristics of vertebrae from different regions of the vertebral column.**
 * 4) **Understand how the intervertebral joints contribute to movements of the vertebral column.**
 * 5) **Describe the ligaments of the vertebral column. Describe the intervertebral disc and the joint in which it is found. Understand the meaning of a "herniated disc."**
 * 6) **Understand how spinal nerves emerge from the vertebral column.**
 * 7) **Describe the craniovertebral joints.**


 * 1) **Define and differentiate between the extrinsic and intrinsic muscle groups associated with the back.**
 * 2) **Study the attachments and functions of the extrinsic back muscles (these muscles will also be considered with the upper extremity)**
 * **Trapezius**
 * **Lattissimus dorsi**
 * **Levator scapulae**
 * **Rhomboids**
 * **Serratus posterior**
 * 1) **Study the attachments and functions of the intrinsic back muscles.**
 * **Splenius capitis and cervicis**
 * **Erector spinae**
 * **Semispinalis cervicis and thoracis**


 * 1) **Study the blood supply of the spinal cord and the vertebral column.**

Introduction
"study early and often" - do not fall behind "I do not write trick questions" Bring clickers to class - questions from previous lecture asked in the beginning of class

Movements of the Back (4 different movements)

 * Flexion - bending forward
 * Extension - bending backwards
 * Lateral Flexion - bending sideways
 * Rotation - rotating the back

Vertebral Column (31-33 vertebrae)

 * The staff will use numbers to denote vertebrae (T12 instead of TXII)
 * 7 cervical
 * 12 thoracic
 * 5 lumbar
 * 5 sacral (usually fused)
 * 2-4 coccygeal (typically fused as well)
 * Vertebrae Prominence - C7 (first vertebrae you can feel on your neck)
 * Sacral hiatus - located posteriorly is an important landmark
 * contains fat and the filum terminale
 * enclosed by a membrane
 * important for caudal anesthesia (epidural)

Curvature of the Back

 * Development
 * primary curvature is concave as a fetus
 * first secondary curvature occurs in the lumbar region after birth due to weight bearing
 * second secondary curvature occurs in the cervical region around age 4
 * Curvatures
 * Primary curvatures: thoracic, sacral/coccygeal
 * Secondary curvatures: cervical, lumbar
 * Pathology
 * accentuated thoracic (primary) curvature: kyphosis (hunch back)
 * accentuated lumbar (secondary) curvature: lordosis (sway back)
 * lateral curvature: scoliosis

Typical Vertebra

 * the vertebral body is located anteriorly
 * the transverse process is located laterally
 * the spinous process is located posteriorly
 * vertebral arch = laminae (lamina is "flat") + pedicles (pedicle is "little foot")
 * vertebral foramen = posterior aspect of the vertebral body + vertebral arch
 * multiple vertebral foramina = vertebral canal (holds the spinal cord)
 * articular processes (articular = "joint")
 * inferior articular facet (facet = "smooth face")
 * superior articular facet
 * intervertebral foramen = superior vertebral notch + inferior vertebral notch (this is where the spinal nerves emerge from the vertebral column, the DRG are in the vertebral canal close to the foramen)

Regional Characteristics of Vertebrae

 * Distinguishing features
 * Body
 * Processes
 * Foramina
 * Zygapophysial Joints (Z-joint) - joints between vertebrae
 * Cervical
 * DIAGNOSTIC: transverse process has a hole in it (transverse foramen) which allows the vertebral artery to pass through
 * some vertebrae have a bifid (2-prong) spinous process which tends to be shorter and angled slightly down
 * the body tends to be small and squarish
 * Z-joint facing superiorly and inferiorly to facilitate rotation
 * Thoracic
 * DIAGNOSTIC: facets on the body (articulate with the head of the rib) and the transverse process (articulate wit the tubercle of the rib). Also note that a rib articulates with facets on the bodies of adjacent vertebrae.
 * the body is heart shaped
 * spinous processes tend to be long and angled sharply downward
 * Z-joint anterior and posterior, least mobile region of the vertebral column
 * Lumbar
 * DIAGNOSTIC: process of elimination! (not cervical or thoracic)
 * very large body, kidney shaped
 * transverse process are large and lateral
 * spinous process are short and stocky
 * Z-joint in the sagittal plane to facilitate flexion and extension

Atlas (C1) and Axis (C2)

 * Atlas (C1)
 * As Atlas was a titan that held up the world, the Atlas vertebrae holds up the skull
 * does not really have a spinous process, instead has a posterior tubercle (tubercles are bumps on bones which tend to attach to muscles or ligaments)
 * does not have a vertebral body, has anterior and posterior arches instead
 * Axis (C2)
 * the remnant of the C1 body is fused to C2: odontoid process/dens
 * otherwise has the typical characteristics of other cervical vertebrae (bifid spinous process, transverse foramen, etc)

Vertebral Ligaments

 * Longitudinal ligaments run on both sides of the vertebral body
 * anterior longitudinal ligament is wider than the posterior
 * posterior longitudinal ligament forms the anterior wall of the vertebral column, supports dorsal and ventral roots
 * Interspinous ligament fills in the space between the spinous processes
 * Supraspinous ligament articulates with the tip of the spinous processes
 * Ligamentum flavum connects adjacent laminae and has a yellowish hue (flavum = "yellow")
 * in the cervical region, the supraspinous ligament is replaced by the ligamentum nuchae which serves as the attachment point for neck muscles. This is also the reason why you cannot palpate C1-C6

Intervertebral Discs

 * Anulus fibrosus - rings of fibrocartilage (anuli = "rings")
 * thinner posteriorly
 * vascularized (has blood supply)
 * Nucleus pulposus - mostly mucoid (70-90% water with reticular and collagen fibers)
 * 25% of adult height is due to the intervertebral discs
 * as a person ages, the water content decreases making it thinner and more easy to rupture
 * this is why a person gets shorter as they age
 * Avascular
 * Nomenclature
 * L4-5 disc = intervertebral disc between L4 and L5 (do not use the old system of nomenclature)
 * There is no C1-2 disc because the C1 body is fused to the C2 vertebrae
 * Herniation
 * most commonly herniates in the posterior and lateral direction in cervical and lumbar regions
 * thoracic herniation is rare
 * A herniation in L4-5 disc will affect the lower nerve root (L5) as the L4 nerve root will leave just below the pedicle and above the herniation. It also will not affect lower nerve roots (S1, etc) as they are able to move out of the way
 * A herniation in the C7-T1 disc will affect the C8 nerve root leaving the area
 * Pain of herniation is from inflammation of nerve covering as it rubs against rupture

Atlanto-occipital Joint

 * Origin = typically proximal and the stable part of the joint
 * Insertion = typically distal and the movable part of the joint
 * The atlantooccipital membrane fills the space between C1 and the occipital bone
 * in the upper cervical region (C2 and up), the posterior longitudinal ligament becomes the tectorial membrane
 * the cruciform ligament (cruciform = "cross-shaped") covers the dens
 * the transverse ligament holds the dens on the anterior arch of the atlas
 * alar ligaments (ala = "wing") attaches the dens to the occipital bone
 * apical ligament holds the dens to the occipital bone superiorly
 * when the dens snaps (hanging, trauma), the spinal cord is severed

Muscles of the Vertebral Column

 * You should know the following (in order of importance)
 * function
 * innervation
 * origins and insertions
 * Suboccipital and transversospinal (deep intrinsic back muscle) are not covered in this course
 * Extrinsic back muscles are also extrinsic muscles of the shoulder and will be covered in the shoulder lecture tomorrow
 * innervated by the ventral rami
 * connect the upper limb to the trunk and control movement of the upper limb

Intrinsic Back Muscles

 * innervated by the dorsal rami
 * maintain posture and control movement of the vertebral column and head
 * Superficial Layer (splenius muscles)
 * Splenius capitis (splenius = "bandage")
 * origin: spinous processes (SP) of the lower cervical/upper thoracic vertebrae
 * insertion: cranium
 * function: extend head (bilateral), lateral flex, rotate face (unilateral)
 * Splenius cervicis
 * Origin: SP of thoracic vertebrae
 * insertion: transverse processes (TVP) of cervical vertebrae
 * function: extend neck (bilateral), lateral flex, rotate neck (unilateral)
 * Intermediate Layer (erector spinae muscles)
 * 3 vertical columns of muscles
 * common origin: ilium (iliac crest), sacrum, lumbar spinous processes, thoracolumbar fascia
 * Iliocostalis (most lateral)
 * insertion: ribs and transverse processes of the cervical spine
 * function: extension of the neck, thorax, and lumbar
 * Longissimus
 * insertion: ribs, transverse processes of the cervical and thoracic spine, cranium
 * function: extend head, neck, thorax, lateral flex cervical region, rotate face (unilateral)
 * Spinalis (most medial)
 * insertion: spinous processes and transverse processes of the cervical and thoracic vertebrae, cranium
 * function: extend head and vertebral column
 * Deep Layer (semispinalis muscles)
 * Semispinalis Capitis
 * know that it is a deep muscle
 * will be asked to ID in lab
 * origin: transverse processes of the lower cervical and upper thoracic
 * insertion: cranium
 * function: extend head
 * Multifidus
 * spans 2 vertebral levels
 * important core muscles
 * erector spinae muscles counteract gravity and keeps you erect

Innervation of the Back

 * the medial branch goes through the muscles to the skin surface to form cutaneous nerves
 * angles of the ribs are the edges of the back dermatomes

Vasculature of the Back

 * Regional "feeder" Arteries
 * Segmental Spinal Arteries
 * Radicular arteries
 * do not supply the spinal cord because they do not meet the three major longitudinal arteries
 * supplies the anterior/posterior, DRG, dorsal roots, and ventral roots
 * Segmental medullary arteries
 * they do supply the spinal cord
 * Ligation of the great segmental medullary artery of Ademkiewicz (accidently cut during surgery) will cause paraplegia because it supplies the lower 2/3 of the spinal cord
 * Cervical Region
 * Vertebral a.
 * Ascending Cervical a.
 * Deep Cervical a.
 * Thoracic Region
 * Posterior Intercostal a.
 * Abdominal Region
 * Lumbar aa.
 * Pelvic Region
 * Lateral Sacral a.
 * Major longitudinal arteries
 * Anterior spinal artery
 * 2 Posterior spinal arteries
 * supply the spinal cord
 * Venous Drainage
 * Internal venous plexus (epidural) is inside the vertebral canal and drains into the external venous plexus
 * External venous plexus is outside the vertebral column