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

Cervical

• 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

Movements:
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

C7

• 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

Sacrum

• 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.