3Structure of the Spine What is the vertebral column? a curved stack of 33 vertebrae structurally divided into five regions:cervical region - 7 vertebraethoracic region - 12 vertebraelumbar region - 5 vertebraesacrum - 5 fused vertebraecoccyx - 4 fused vertebrae
5Structure of the Spine What is a motion segment? two adjacent vertebrae and the associated soft tissuesconsidered the functional unit of the spine
6Interspinous ligament Posterior longitudinal ligament Structure of the SpineSupraspinous ligamentIntervertebral joint and facetSpinous processLigamentum flavumInterspinous ligamentTransverse processAnterior longitudinal ligamentCartilaginous end-plateIntervertebral discIntervertebral foramen with nerve rootPosteriorAnteriorVertebral canalPosterior longitudinal ligamentVertebral bodyTwo adjacent vertebrae and the associated tissues comprise the motion segment.
7Structure of the Spine What are the joints between adjacent vertebrae? intervertebral symphysis joints on the anterior sidetwo gliding diarthrodial facet joints on the posterior side
8Structure of the Spine What is the function of the facet joints? to channel and limit the range of motion in the different regions of the spineto assist in load bearing, sustaining up to 30% of the compressive load on the spine, particularly when the spine is in hyperextension
9Structure of the Spine What are the intervertebral discs? fibrocartilaginous discs that cushion the anterior spinal symphysis jointscomposed of a nucleus pulposus (colloidal gel with a high fluid content) surrounded by the annulus fibrosus (a thick, fibrocartilaginous ring that forms the disk exterior)
10Cervical Vertebra Picture retrieved from CervicalVertebra
11Structure of the Spine What are the primary spinal curves? the thoracic and sacral curvesconcave anteriorlyare present at birth
13Structure of the Spine What are the secondary spinal curves? the lumbar and cervical curvesconcave posteriorlydevelop from supporting the body in an upright position after young children begin to sit and stand
14Cervical Vertebra Picture retrieved from Picture retrieved from
15Lumbar Vertebra Picture retrieved from LumbarVertebraPicture retrieved from
19Movements of the Spine What movements of the spine are allowed? The movement capabilities of the spine are those of a ball and socket joint, including movement in all three planes and circumduction.Mechanically:Annulus fibrous – acts like coiled springNucleus pulposus – acts like ball bearing
20Movements of the SpineWhat muscles contribute to flexion of the spine in the cervical region?rectus capitus anteriorrectus capitis lateralislongus capitislongus collieight pairs of hyoid muscles
24Movements of the SpineWhat muscles contribute to extension of the spine in the cervical region?splenius capitissplenius cervicisassisted by:rectus capitis posterior major and minorobliquus capitis superior and inferior
26Movements of the SpineWhat muscles contribute to extension of the spine in the thoracic and lumbar regions?erector spinae - spinalis, longissimus, iliocostalissemispinalis - capitis, cervicis, thoracisdeep spinal muscles - mulitifidi, rotatores, interspinales, intertransversarii, levatores costarumPicture retrieved from
27Movements of the SpineWhat muscles contribute to lateral flexion of the cervical spine?sternocleidomastoidlevator scapulaescalenus anterion, posterior, & mediusPLUS the cervical flexors and extensors when developing tension unilaterally
31Loads on the Spine What forces commonly act on the spine? body weight tension in the spinal ligamentstension in the spinal musclesany external loads carried in the hands
32Loads on the SpineIn normal standing position, body weight acts anterior to the spine, creating a forward bending load (moment) on the spine.
33Loads on the SpineFcFswtBecause the spine is curved, body weight, acting vertically, has components of both compression (Fc) and shear (Fs) at most motion segments.
34Compression reaction force Loads on the SpineMuscle tensionShear reaction forceCompression reaction forceJoint centerDuring lifting, both compression and anterior shear act on the spine. Tension in the spinal ligaments and muscles contributes to compression.
35Sample Problem 1How much tension must be developed by the erector spinae with a moment arm of 6cm from L5-S1 joint center to maintain the body in the position shows on your right?Given thatHead : 58 N Arms : 81 NTrunk : 328 N Box : 111 N
36Loads on the SpinecompressiontensionLumbar hyperextension can create a bending load (moment) in the posterior direction.
37Loads on the SpinehyperextensionLumbar hyperextension produces compressive loads at the facet joints.
38Loads on the Spine Superior view Lateral view Spinal rotation generates shear stress in the intervertebral discs.