Lecture 16 + 17 - SQ

Question 1

1. What are the features of typical vertebrae in each region? What are the features of atypical
   vertebrae?

Answer 1

1. The features of typical vertebrae in each region are:
   Cervical region: the typical cervical vertebra has: the body is oblong in shape. Has a bifid
   spine. The neural or vertebral arch is wide. The presence of foramen transversarium.
   The atypical cervical vertebrae are: the 1st, the 2nd, and the 7th
   .
   The 1st cervical vertebra or ATLAS has no body, has two arches: one anterior arch and one
   posterior arch, has no spine, but has a foramen transversarium in its transverse process, has a
   kidney-shaped facet in its upper surface, and a rounded facet in its lower (or inferior) surface.
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   The 2nd cervical vertebra or AXIS has a body with an upward projection anteriorly called the
   odontoid process (or dens), has a bifid spine and a foramen transversarium in its transverse
   process. The upper articular facet is rounded and the lower articular facet is flat.
   The 7th cervical vertebra has a long tuberculated spine (not bifid) and has a foramen in its
   transverse process, and is called the vertebra prominens because of its long prominent spine.
   Thoracic region: the typical thoracic vertebrae are the 2nd to the 9th; they have 2 demi-facets
   on the sides of the body of the vertebra and a facet on the transverse process, these are for
   articulations with the head of the rib on the body of the Vertebra and the tubercle of the rib
   with the transverse process.
   The atypical thoracic vertebrae are the 1st, 10th, 11th, and 12th
   .
   The 1st thoracic vertebra has an entire articular facet for the head of the first rib, and a demifacet for the upper half of the head of the second rib.
   The 10th thoracic vertebra articulates with the 10th rib only by a complete facet.
   The 11th thoracic vertebra has one facet for articulation with the head of the 11th rib, and has
   no facet on its transverse process.
   The 12th thoracic vertebra has one facet for articulation with the head of the 12th rib, and has
   no facet on its transverse process.
   Thoracic vertebrae from 1 to 10 have facets on their transverse processes for articulation with
   the tubercles of the ribs of the same number.
   Lumbar region: The upper 4 lumbar vertebrae are typical. Their bodies are larger than those
   of the thoracic vertebrae. There are no facets for ribs on their bodies, nor facets for tubercles
   of the ribs on their transverse processes.
   The 5th lumbar vertebra has a large body and the pedicles articulate partly on the body
   posteriorly and on the transverse processes as well.
   Sacral region: The 5 sacral vertebrae fuse together to form a triangular bone called the
   SACRUM. The sacrum has a wide base upwards and its Apex tapers downwards. Between the
   bodies of the fused sacral vertebrae anteriorly, there are 4 anterior sacral foramina and
   posteriorly also there are 4 posterior (or dorsal) sacral foramina. These sacral foramina are
   connected to the sacral canal which lies between the bodies of the sacral vertebrae and their
   vertebral arches. The sacral foramina are for the passage of sacral nerves. The anterior border
   (or margin) of the body of the first sacral vertebra is prominent and is called the sacral
   promontory. The first sacral vertebra articulates with the 5th lumbar vertebra both by its
   body and articular processes to form the lumbosacral joint.
   The lateral borders of the sacrum are thick and contain an articular ear-shaped, or auricular,
   area in the upper (or first) three sacral vertebrae to articulate with similar auricular areas
   present on the inner posterior aspects of the hip bones to form the sacro-iliac joints. The
   spines of the upper 4 sacral vertebrae fuse together to form the sacral crest, while the lower
   spine is absent forming a gap called the sacral hiatus. The lower part or apex of the sacrum
   articulates with first coccygeal vertebra to form the sacro-coccygeal joint.
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   Coccygeal vertebrae: are 4 rudimentary vertebrae. The first coccygeal vertebra is usually
   separate and has two cornua (or horns) on the sides of the body to articulate with the two
   cornua and body of the 5th sacral vertebra by ligaments to form the sacrococcygeal joint.

Question 2

2. What are the normal curvatures (primary and secondary) of the human spine and how and
   when do these curvatures develop?

Answer 2

2. The human spine (or vertebral column) is originally, during development of the embryo,
   concave from above downward. This is called the primary curvature. After delivery, and
   when the baby starts to move his head, a posterior curvature develops in the cervical region.
   During standing and walking develops a lumbar curve, concave anteriorly. These are called
   secondary curvatures. The thoracic and pelvic curvatures are the primary curvatures while
   the cervical and lumbar curvatures are the secondary curvatures of the vertebral column (or
   spine).

Question 3

3. Where are the ligaments that tie the bony segments (vertebrae) of the spine together?

Answer 3

3. The ligaments which tie the bony segments, or vertebrae, in the vertebral column are:
   Anterior Longitudinal ligament - lies in front (anterior) to the bodies of the vertebrae and their
   intervertebral discs.
   Posterior Longitudinal ligament - lies behind (posterior) to the bodies of the vertebrae and
   their discs.
   Ligamenta flava - lie between the laminae of the vertebrae.
   Interspinous ligaments - lie between the spines of the vertebrae.
   Supraspinous ligaments lie above the spines of the vertebrae.
   Ligamentum Nuchae is a combination of both the supraspinous and interspinous ligaments
   and is present in the neck.
   Intertransverse ligaments lie between the transverse processes.
   Capsular ligaments connecting the articular processes of the vertebrae.
   Ligaments that connect the heads and tubercles, of the ribs with the thoracic vertebrae.
   Other ligaments connect the atlas with the occipital bone of the skull.

Question 4

4. Describe the general structure of the spinal cord and its nerve roots (dorsal and ventral); also
   the relationships of the meninges to these structures?

Answer 4

The spinal cord is made up of nerve cells and their fibres, i.e., grey matter and white matter.
The nerve cells (or neurons) form an H-shaped structure in the centre surrounded by the white
fibres which form the nerve tracts or fasciculi. There is a small hole in the centre of the grey
matter called the central canal of the spinal cord for the passage of C.S.F. (cerebrospinal
fluid).
The posterior part of the grey matter is called the posterior horn and is connected to the dorsal
root ganglion by the fibres of the sensory part of the spinal nerve, while the ventral or
anterior part of the grey matter is called the ventral horn. The ventral horn contains the
motor neuron cells that give origin to the ventral or anterior root of the spinal nerve
which is motor. So the spinal nerve is a mixed nerve composed of anterior root (motor) and
a posterior root (sensory) connected to the dorsal root ganglion.
In the thoracic and upper lumbar region of the spinal cord there is another horn called the
lateral horn that has connections with the sympathetic nervous system (which is part of the
Autonomic Nervous System.)
The spinal cord, as in the brain, is surrounded by 3 layers of meninges (or coverings) from
inside out are the pia mater, the arachnoid and the dura mater.
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Between the pia mater and the arachnoid is a space called the subarachnoid space
containing the CSF and the blood vessels (arteries and veins) that supply the brain and spinal
cord.
The dura mater of the brain with the other meninges are continuous with the meninges that
cover the spinal cord. The meninges also continue over the spinal nerves until they exit from
the intervertebral foramina where the dura mater will blend with the neurilemmal sheath of the
spinal nerve.

Question 5

5. What is the location and the content of the epidural space and lumbar cistern?

Answer 5

The location of the epidural space is between the bony vertebral canal, or the skull, and the
dura mater. Its contents are blood vessels, plexuses of veins and fat (in case of the spinal
cord).

Question 6

6. What bony and soft tissues form the intervertebral foramina of the cervical and lumbar
   regions of the spine?

Answer 6

6. The boundaries of an intervertebral foramen in the cervical and lumbar regions of the
   vertebral column are:
   Anteriorly: the body of the vertebra above, the intervertebral disc and the body of the
   vertebra below. In the cervical region only synovial joints are present (joints of Luschka)
   with its joint capsule.
   Posteriorly: the inferior articular facet of the vertebra above, the superior articular facet of the
   vertebra below and the synovial joint between them with its capsule.
   Superiorly: the lower part of the pedicle above.
   Inferiorly: the upper part of the pedicle below.

Question 7

7. What is the relationship of the nerve roots to bone and soft tissue as they emerged through the
   intervertebral foramina of the cervical and lumbar spines?

Answer 7

7. The cervical nerves, when they exit through the intervertebral foramina, lie above the vertebra
   of the same number. In the lumbar region the spinal nerves exit below the vertebra of the
   same number.

Question 8

8. What is the classification and location of all joints of the vertebral column, and between the
occipital bone (of the skull) and the atlas?

Answer 8

8. Classification of joints of the vertebral column are as follows:
   Between the bodies of the vertebrae there are the intervertebral discs so the joints here are
   fibro-cartilaginous joints called symphyses.
   Between the articular processes of the vertebrae are synovial joints.
   Joints between the laminae are fibrous joints connected by the ligamenta flava.
   The joints between the condyles of the occipital bone of the skull and the atlas vertebra are
   synovial joints.

Question 9

9. What is the plane (orientation) of the facet/synovial joints and how does this contribute to or
   limit movements of the spine?

Answer 9

9. The articular facets in the cervical and thoracic vertebrae are flat. The upper articular facets
   are directed backwards and the lower articular facets are directed forwards, so the movement
   between the facets is a gliding movement allowing rotation and flexion and extension. The
   facets in the lumbar vertebrae are different: the upper facets are concave, the lower facets are
   convex, so the movement of rotation is limited, and there is considerable flexion and
   extension.

Question 10

10. What is the structure or composition of an intervertebral disc? What is the contribution of
    intervertebral discs to the length, normal curvatures and movements of the spine?

Answer 10

10. An intervertebral disc is made from an outer fibrous ring called the anulus fibrosus and
    central jelly-like mass called the nucleus pulposus (remains of the notocord of the embryo).
    The length of the intervertebral discs is about 1/4th the length of the spine (or vertebral
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    column). These intervertebral discs act like cushions helping to maintain the normal
    curvature of the spine as well as acting as shock absorbers.

Question 11

11. What is the location, general attachments and motor nerve supply of the primary movers of
    the spine? What movements are assisted by these muscle groups?

Answer 11

11. The primary movers of the spine are the intrinsic muscles that are attached to the back of the
vertebral column (i.e., the spines, the laminae and the transverse processes) and they assist in
extension of the spine. They are supplied by the dorsal (or posterior) rami of the spinal
nerves.

Question 12

12. What are the general attachments, motor nerve supply and actions of the superficial and
    intermediate muscles of the back?

Answer 12

12. The general attachments of the muscles of the back are to the transverse processes, the spine
    and the laminae of the vertebra and the dorsal aspect of the sacrum. Their motor nerve supply
    is from the posterior (dorsal) rami of spinal nerves (as segmental nerve supply). The
    superficial muscles of the back are mostly related to the upper limb and they are supplied by
    nerves from the brachial plexus (i.e., ventral rami of cervical spinal nerves).

Question 13

13. What are the functional components and general distribution of both dorsal and ventral rami
    of spinal nerves?

Answer 13

13. A spinal nerve (which is mixed sensory and motor) will divide later into a ventral (anterior)
    ramus and a dorsal (posterior) ramus. The ventral rami of the cervical, lumbar and sacral
    nerves will form plexuses and distribute their nerves to muscles and skin and joints of the
    neck, upper limb and lower limb. The ventral rami of thoracic (or intercostal) nerves go to
    supply intercostal and anterior abdominal wall muscles and skin without forming plexuses.
    The posterior or dorsal rami of spinal nerves never form plexuses and they supply intrinsic
    muscles of the back as well as the skin of the back.