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26. The anatomy and development of the vertebral column. The histology of the thymus.

26 Dec

26. The anatomy and development of the vertebral column. The histology of the thymus.

Anatomy: vertebral column.

Vertebral Column

33 vert
= 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral vert, 4 fused coccyx vert

Parts of Vertebral Column

Parts of Vertebral Column


  • bifid spinous process (short)
  • foramina w/in transverse process = transverse foramina for vert a/v/n
  • smaller body w/ sup surface concave, inf surface convex
  • neural arch for med primarily by laminae
  • very short pedicles
  • transverse processes have ant/post tubercle for scalene m


most mobile of all vert
b/c curved bodies = flex/extention
shallow slope/ant process = lat flexion
atlas/axis = rotation

Special cervical vertebrae:
C1 atlas

  • no body, supports skill
  • widest of Cervical vertebrae
  • ant/post arches + paired trans processes
  • w/ occ condyles sup = atlanto-occipital joints
  • w/ axis inf = atlanto-axial joints

C2 atlas

  • smallest transverse process
  • characterized by dens = odontoid process
  • projects sup into ant arch of atlas
  • making pivot point around atlas = rotation


  • makes the vertebral prominence
  • long horizontal, one head spinous processes
  • covered w/ nuchal lig, supraspinous lig, back m

Thoracic vert

  • get bigger T1 –> T12 (bodies)
  • costal facet to articulate w/ ribs
    • @ where pedicle med body (sup)
    • @ end of trans process of ribs (inf)
  • spinous process = point downward, overlapping below
  • Movement = min flexion, lat flexion, rotation

Lumbar vert

  • Massive body
  • small & strong transv process, point back
  • almost NO Rotation:
    • -Upper face in (art facets)
    • -Lower are in & face out
  • Movement: flex, ext, lat flexion
  • L5 = largest, have mammillary and accessory processes


  • large wedge shaped bone
  • 4 pairs of foramina ->
    • ant = pelvic sacral foramina = ant rami of S1-S5
    • post = dorsal sacral foramina = post rami of S1-S5
  • makes post part of pelvic brim
  • provides stability for pelvis

Bony Markings:
sacral promontory = ant edge of S1
Ala = massa lata w/ hip bones = sacro-iliac joint
Med sacral crest
Sacral hiatus = lamina of S5 not fused, locks like upside down “V”

Curvatures of Spine:

  • 4 curvatures: cervical, thoracic, lumbar, sacral
  • provide flexible support
  • thoracic & sacral curve post – are the primary curves = develop from embryonic life
  • cervical & lumbar curve ant – are the secondary curves = develop in life

    • cervical = happens when infant holds his head up
    • lumbar = happens when infant begins to walk and is upright
    • caused by diff thicknesses of ant/post parts of IV disks

IV Joints:
1/4 of total spinal cord length
holds weight of spine
flexable enough to allow movement

Disk –> none b/w atlas & axis
1. Anulus fibrosis
concentric layer of fibrous cartilage & tissue
bind vert column together
absorbs SHOCK

2. Nucleus pulposis

remnant of embryonic notochord
reticular/ collagen fiber w/in mucus
equalize pressure, absorb shock

Vert Column Ligs
Intraspinous lig –> b/w lower edge of 1 to upper edge of next
Supraspinous lig –> across spinous pr, merge w/ intraspinous lig

Nuchal lig
is thickened supraspinous lig from C7 –> ext occ protuberance
makes triangular fibrous septum med b/w musc on post side of neck

Ligamentum Flavum

holds laminae together, maintain upright posture
pierced during Lumbar puncture to get CSF
yellow fibroelastic tissue

* all 3 above limit flexion of vertabrae column

Ant longitudinal lig – front and side of vert bodies
stronger than post, skull –> sacrum
widens as goes down, inc stability as weight increase
supports anulus fibrosus ant

Post longitudinal lig
– on vert canal on backs of bodies
narrow @ the body of vert, wider @ disks
narrows as desc,
support post bodies & anulus fibrosus post

Muscles of Vertebral Column
Paravertebral m – covered by fascia, ext, rot of Head & Neck, Trunk
1.Short rotator m – transv process of 1 –> spinous pr. base of vert above
2.Long rotator m – transv process of 2 –> base of sp pr of 2 vert above
3. Multifundous m – transv process of 1 –> side of sp pr of 3-5 vert above
*all 3 =  rotation of upper spine to opp side

Erector spinae m
– sacrum –> upper thorax
Joined @ origin, arise from a tendon that originate from spines of L1-5, iliac crest, post sacrum

  1. Spinalis – inserts of sp pr of upper Thoracic vert
  2. Longissimus – lower 9 ribs, transv pr. of vert next to them & mastoid process
  3. Iliocostalis lumborum – lower 6 ribs
  • *Ext, rotate, lat flex of vert column & head
  • One side only = lat flexion
  • Both sides = ext of Lumbar/thoracic spine

NOTE – Splenius, Longissimus cervicis, semispinalis are also vert m, but in neck mostly, so covered in that topic


Spinal Cord

  • upper 2/3 of vert canal
  • covered by 3 meningeal layers:
    • Pia, Arachnoid, Dura
    • b/w pia & arachnoid = subarachnoid space = CSF
    • b/w dura & vert canal wall = epidural space = fat, CT, a/v
      • CLINICAL NOTE =  epidural anasthetic
    • Dural sac (open sup, tapers as desc to S2) – cont w/ dura of brain
  • spinal cord connects to dura layer = denticulate lig

Cervical & Lumbar parts larger to make Brachial & Lumbar & Sacral plexus

In Embryonic life, cord runs whole length of vert column
but after birth, spinal column grows faster than cord
so cord end @ L1-2, spliting into branches
= Cauda Equina



Histology: The histology of the thymus.

Embryology: development of the vertebral column.