Download Anatomy Ch 2 101-111 [4-20

Anatomy Case 2 Ch. 2 101-111
Anatomy Ch. 2 101-111
Spinal Cord
-Spinal cord extends from foramen magnum to between L1 and L2, but can end earlier at T12
-In neonates, can end as low as L4
-Conus Medullaris – distal end of spinal cord (cone shaped)
-pial extension of connective tissue from bottom of cord is called filum terminale
-Spinal cord is not uniform, it has 2 major swellings
1. Cervical Enlargement occurs because of brachial plexus in C5-T1
2. Lumbosacral Enlargement occurs between L1-S3 to innervate lower limbs
-Anterior median fissure extends the length of the anterior surface
-Posterior median sulcus extends along posterior surface
-Posterolateral sulcus on each side of the posterior surface marks where posterior rootlets enter cord
-Gray matter is rich in nerve cell bodies, forming longitudinal columns along cord, butterfly cross section
-White matter surrounds gray matter and is rich in nerve cell processes forming large bundles or tracts
that ascend or descend in cord to other spinal cord levels
Vasculature – two sources of blood supply to the spinal cord
1. Longitudinal vessels arising superior to cervical portion of cord and descending along surface
a. Consist of Anterior spinal artery, originating in cranial cavity as union of two vessels
that arise from vertebral arteries resulting in one artery descending inferiorly in anterior
median fissure
b. Also consists of TWO posterior spinal arteries which originate in cranium and arise from
a terminal branch of each vertebral artery and descend along spinal cord in the
posterolateral sulci and the connection of posterior roots in spinal cord
2. Feeder arteries entering vertebral canal through intervertebral foramina at every level… also
known as segmental spinal arteries arise from vertebral and deep cervical arteries in neck,
posterior intercostal arteries from thorax, and lumbar arteries in abdomen
a. Give rise to anterior and posterior radicular arteries at every vertebral level which
follow and supply the nerve roots
b. Can also give off segmental medullary arteries passing directly to longitudinal vessels
-Ant. and Post. Spinal arteries reinforced by 8-10 segmental medullary arteries, largest of which is
arteria radicularis magna or the artery of adamkiewicz. This artery arises in lower thoracic/upper
lumbar region on left side to support the lumbar enlargement
Veins – form number of longitudinal channels to drain cord
1. Two pairs of veins on each side bracket connections of posterior and anterior rootlets
2. One midline channel parallels anterior median fissure
3. One midline channel passes along posterior median sulcus (posterior spinal vein)
-longitudinal channels drain into extensive internal vertebral plexus in extradural space that drains into
azygos system of veins, also communicating with intracranial veins
Spinal Dura Mater – outermost meningeal membrane and separated from bones by extradural space
-continuous with inner meningeal layer of cranial dura mater at foramen magnum
-inferiorly, dural sac narrows at level of lower border of SII and forms investing sheath for pial part of
filum terminale
-attaches to posterior surface of coccyx
Anatomy Case 2 Ch. 2 101-111
Arachnoid Mater – thin membrane against, but not adherent to deep surface of dura mater, deep to it
is the subarachnoid space. Arachnoid mater ends at SII
Subarachnoid Space – contains cerebrospinal fluid and is continuous at foramen magnum with brain
CSF. Terminates at SII.
-Arachnoid Trabeculae – tissue strands continuous with arachnoid mater on one side of pia
mater and arachnoid mater on the other spans subarachnoid space to interconnect the two
membranes
-Blood vessels are suspended in subarachnoid space by similar trabeculae, expand over vessels
to form a coat
-Subarachnoid space is largest in the region inferior to the terminal end of the spinal cord where it
surrounds the cauda equine. CSF can be withdrawn from lower lumbar region without injuring the cord
at LIV
Pia Mater – vascular membrane that firmly adheres to spinal cord, extending into anterior median
fissure and reflects as sleeve-like coatings onto posterior and anterior rootlets as they cross
subarachnoid space
-Denticulate Ligament – longitudinally oriented sheet of pia mater extending laterally toward arachnoid
and dura mater
-attached medially to spinal cord in a plane that lies between origins of ant. and post. Rootlets
-laterally, it forms triangular extensions along free border with apex of each extension anchored
through arachnoid mater to dura mater
-generally occur at exit points of adjacent anterior and posterior rootlets and position the spinal cord in
center of subarachnoid space
Arrangement of Structures in Vertebral Canal –
-Anteriorly: bodies of vertebrae, intervertebral discs, posterior longitudinal ligament
-Laterally: on each side by the pedicles and interverterbral foramina
-Posteriorly: laminae and ligamenta flava, and in the median plane the roots of interspinous ligaments
-Extradural sac contains vertebral plexus of veins in fatty connective tissue
-Spinous processes can be palpated through skin in thoracic and lumbar regions of back
-Lumbar Puncture: Needle passes through supraspinous ligamentinterspinous ligamentextradural
spacethrough dura and arachnoid matter and into subarachnoid space
Spinal Nerves – connected to spinal cord by posterior and anterior rootlets
-Posterior root- contains processes of sensory neurons carrying info to CNS, cell bodies in dorsal root
ganglia at distal end of posterior root in the intervertebral foramen
-Anterior root- contains motor nerve fibers carrying signals away from CNS, cell bodies are in anterior
regions of cord
-Medially- post and ant roots divide into rootlets which attach to the cord
Spinal Segment – area of cord that gives rise to post and ant rootlets  forming spinal nerve
-each spinal nerve divides after emerging from intervertebral foramen into posterior ramus and a larger
anterior ramus
Posterior rami – innervate only intrinsic back muscles (epaxial) and narrow strip of skin on back
Anterior rami – innervate most other skeletal muscles of body (hypaxial muscles), except for head
Sinuvertebral (recurrent meningeal) nerves – located at point of division into anterior and posterior
rami, re-enter intervertebral foramen to supply dura, ligaments, intervertebral discs, and blood vessels
-all plexuses (cervical, brachial, lumbar, sacral) formed by anterior rami
Anatomy Case 2 Ch. 2 101-111
-Spinal cord is shorter than vertebral column, so roots of spinal nerves get longer and pass more
obliquely from cervical to coccygeal regions of vertebral canal
-posterior and anterior roots emerging between vertebrae in lower regions of cord actually connected
to cord at higher levels
-below the end of the cord, the posterior and anterior roots of lumbar, sacral, and coccygeal nerves pass
inferiorly to reach exit points from vertebral canal called Cauda Equina
Nomenclature of Nerves: C1-C8, T1-T12, L1-L5, S1-S5, Co (coccygeal)
Lumbar Cerebrospinal Tap – lumbar tap is carried out to get CSF but also to inject antibiotics,
chemotherapy, and anesthetics into subarachnoid space.
-since spinal cord terminates at between L1 and L2 but subarachnoid space extends to SII, large CSF
filled space containing lumbar and sacral nerve roots but no cord
-this is where we extract spinal fluid
-patient placed lateral or prone, needle passed in midline between spinous processes into extradural
space through dura and arachnoid mater into subarachnoid space
-needles push roots away from tip so as not to cause symptoms
-Anesthetics can be injected into extradural or subarachnoid space to knock out sacral and lumbar nerve
roots for operations on pelvis and legs without need for general anesthesia
-patient must be erect and not lying on side or head down
-if patient on side, anesthetic will be unilateral
-if patient head down, anesthetic will pass cranially and depress respiration
-in some cases, anesthesiologists choose to carry out extradural anesthesia, where needle is placed
through skin, supraspinous ligament, interspinous ligament, and ligamenta flava into areolar tissue and
fat around dura mater to anesthetize exiting nerve roots and diffuse into subarachnoid space
Herpes Zoster – virus that produces chickenpox that remains dormant in cells of DRG. During breakout,
rash ensues in dermatome of DRG
Back Pain – Alternative Explanations – back pain common affecting all individuals. Need to identify
where pain comes from (either vertebral column or related structures)
-pain may be referred to back from organs in retroperitoneum
-Pancreatic Pain – refers to the back and may be associated with pancreatic cancer and pancreatitis
-Renal Pain – may be produced by stones in collecting system or tumors refers to the back
-not usually unilateral, but can produce central posterior back pain
-Enlarged lymph nodes in pre- and para-aortic regions may produce central posterior back pain and may
be a sign of solid tumor malignancy, infection, or Hodgkin’s Lymphoma.
-Enlarged abdominal aorta (aortic aneurysm) may cause back pain (acute in first instance)
-Back pain must be assessed not only of vertebral column but also chest and abdomen