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CERVICAL SPINE

-  All cervical nerves are mixed nerves except C1
     which is pure motor nerve
-  Has 7 cervical vertebrae; 1st 2 are atypical vertebrae

-  C1: ATLAS	
  -  no vertebral body
  -  Ring shaped

-  C2: AXIS
  - has vertebral body but with bifid spinous process
  - Has an upward projection called odontoid process which is believe to
      be congenitally fused vertebral body of C1 (odontoid process
      articulates with anterior arch of C1 and this articulation is
      believed to be true synovial joint which means that if a patient has
      RA of the C1-C2, this articulation can become inflamed.
-  There’s no IV disc between C1 and C2 so that C2 will be able to reach
     C1 and because of this, the primary movement is rotation
     (most commonly occurs in C1-C2)

-  C3 – C7: typical vertebrae
-  With IV disc
-  Has vertebral body
-  Has transverse process
-  Have an articulation found at the posterolateral margin of vertebral
     body.
-  If this posterolateral margin of the vertebral staked up, they will
     form a fused/functional jt because it has no synovial tissue and
     these are called anchovertebral joint, luschska joint or neurocentral
     jt.

VERTEBRAL SPINE:
- 8 pairs cervical nerve in 7 cervical vertebrae, 12 pairs thoracic 
     nerves; 5 pairs lumbar; 5 pairs sacral; 1 coccygeal nerve = total
     of  31 pairs of spinal nerve
- Facet jt: articulation at the posterior aspect of the vertebra
- Facet jt at
               cervical spine is oriented at 45°
               Thoracic spine                      60°
               Lumbar spine                        90°

- Because it is oblique at the cervical & thoracic spine – movt occurring
     is rotation
- Because it is at sagital plane in lumbar spine – flexion & extension
- Entire height of spine ¼ of which is contributed by IV disc

- IVD made up of gelatinous material in the inside that is called 
     nucleus pulposus and fibrous material outside known as annulus fibrosus
     (concentric lamellae of collagen fibers)

	: Fxns of IVD – shock absorber (proteoglycan)
		          - Tensile strength (annulus fibrosus)
	: Nucleus pulposus – made up of collagen and proteoglycan
          (88% responsible for water binding capacity; capacity;
          hydrodynamic property, shock absorber & axial 
          compression distributes stress equally)

		- Proteoglycan decreases as one grows old 
         (increases age; 2nd /3rd decade) so water content decreases,
          therefore IVD becomes more fibrous (increses collagen 
          decreases hydrodynamic) = deceases ability to withstand 
          stress; distributes unequal stress = prone to DJD 

- Supporting structures – Sharpey’s fibers, vertebral end plate, ALL,
     PLI
- IVD is connected to the vertebra above & below by the way of Sharpey’s
     fibers on outer portion (periphery) and inner portion (central) by 
     vertebral end plate 

ALL –thick and strong ligament anterior to the spine
	  - Most strained during extension activities
         - Annulus fibrosus is connected to ALL

PLL –not as strong, thick & wide as ALL; posterior to the spine
        -So, disc herniation is common posteriorly (posterolateral) 
unless there’s trauma causing the IVD to herniate anteriorly
  	 -IVD blends with PLL
	 -Tapers at lumbar & sacral spine
	 -Lumbosacral region is the most common site for disc herniation
	 -PLL, interspinous lig, ligamentum flavum prevent hype 
          flexion injuries

- Any structure in the neck that receives innervation is a potential 
  source of pain (potential pain generators), so all structures in the
  neck are innervated although some are partially innervated
- Misconception: IVD is not innervation
    -NP – no innervation
    -AF – innervated
          -  Ant 2/3 is supplied by vertebral nerve  
          - Post 1/3 is supplied by synovertebral/recurrent nerve of 
            Luschka which also supply PLL & pedicle

- Most mobile portion of spine in cervical region C4-C5, C5-C6, 
     C6-C7 (most disc herniation, fx & dislocation occurs in this
     segments)
- C1- supplied by ventral posterior rami of C1 it between atlas and 
     occipital condyles.
- C2- supplied by ventral rami of C2 or 2nd cervical nerve
- C8- exist between 7th cervical & 1st thoracic
- L5S1- thin PLL, so herniation is posterolateral
- Disk rupture are L4L5 involves L5 nerve root which emerges between 
     L5S1
- Disk rupture at L5S1 involves S1 nerve root which sits between S1S2
- Spinal cord ends at L1L2 and beyond this is no spinal cord is seen 
     only cauda equina, conus medullaris
- If disc herniation is very big condition changes it can impinge 
     both L4 & L5 nerve root. 



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