2.2 Anatomy and Sono-Anatomy of the Spine Flashcards
how many cervical vertebrae in the human spine?
7 cervical
how many thoracic vertebrae in the human spine?
12 thoracic
how many lumbar vertebrae in the human spine?
5 lumbar
how many sacral vertebrae in the human spine?
5 FUSED sacral
how many coccygeal vertebrae in the human spine?
4 FUSED coccygeal
purpose of the 33 vertebrae in the human spine
serve to protect the spinal cord and support weight
which nerve root controls motor (vroom vroom) function?
ventral
which nerve root controls sensory function?
dorsal
the primary curvature of the vertebral column is concave ___________
anteriorly
what two regions of the spine are primary curvatures?
thoracic and sacral
(concave anteriorly)
the secondary curvature of the vertebral column is concave ___________
posteriorly
what two regions of the spine are secondary curvatures?
cervical and lumbar
(concave posteriorly)
the most prominent vertebra in the neck is at level:
C7
the inferior angles of the scapula are at level:
T7
the line that connects the two iliac crests is:
L4
the posterior superior iliac spine is at level:
S2
when viewed laterally, the cervical and lumbar curves are _______ anteriorly
convex
when viewed laterally, the thoracic and sacral curves are _______ anteriorly
concave
spinal curves play a significant role in:
the distribution of local anesthetics (especially during a spinal)
each vertebra consists of a vertebral _______ and a vertebral _______
body; arch
the vertebral ______ is anterior (the major weight-bearing component of the bone)
body
the vertebral ______ is anchored to the POSTERIOR SURFACE of the vertebral body by 2 pedicles and forms what two walls of the vertebral canal?
arch; lateral and posterior
the _________ ________ is created by joining the PEDICLES and LAMINAE
transverse process
the __________ _________ is formed by the FUSING of the LAMINAE
posterior spinous process
what two sites are the safest for spinals and epidurals? why?
L2/3 and L3/4
largest aperture and least neural tissue
the posterior spaces between vertebral arches becomes WIDER by _______ of the vertebral column
flexion
what are interlaminar foramen? (hint: triangle-shaped)
space between the spinous processes of the proximate lumbar vertebrae
what is the sacral hiatus?
failure of the 5th sacral laminae to fuse at the midline, creating an inverted “V” shaped defect in the sacrum
what is the sacral hiatus covered by? (hint: easy to palpate in children)
(thick) sacrococcygeal ligament
which ligament lines the anterior surface of the vertebral column?
posterior longitudinal ligament
this ligament connects the cervical, thoracic, and lumbar SPINOUS PROCESSES from C7 to the sacrum
supraspinous ligament
which ligament is fused between the supraspinous ligament and ligamentum flavum? (hint: it passes between adjacent vertebral spinous processes and “anchors” our needle)
interspinous ligament
this ligament anchors the laminae and limits forward flexion of the spine
ligamentum flavum
small vessels from the ______ _____ penetrate the ligamentum flavum to supply blood
vertebral plexus
why might the supraspinous ligament and ligamentum flavum have limited flexion in older patients?
calcification
the spinal cord is surrounded by what 5 things (in order?)
pia mater
subarachnoid space
arachnoid mater
subdural space
dura mater
where do we deposit local anesthetic for spinals?
subarachnoid space
between the pia and arachnoid matter, this space is filled with ~150 mLs of CSF
subarachnoid space
the pia matter ends at the ____ ______ which anchors the spinal cord to the coccyx
filum terminale
where is the epidural space located?
between the periosteal lining of the canal and the dura
the epidural space is limited anteriorly and posteriorly by the:
posterior longitudinal ligament (anteriorly) and ligamentum flavum (posteriorly)
distance from the skin to the anterior surface of the ligamentum flabum
4-5 cm (normal body habitus)
size of the epidural space
5-7 mm
before exiting the foramens, the nerve roots:
leave the cord and traverse the epidural space
what does the epidural space contain? (name 3)
lymphatic vessels
small arteries
valveless veins
epidurals and spinals are done below ___ so there is no risk of hitting the spinal cord
L1
in what two regions is the spinal cord thickest?
cervical (C5 to T1) = innervates upper limbs
and lumbar (L1 to S3) = innervates lower limbs
in adults, the spinal cord extends from the foramen magnum and terminates at the: (adults and children)
conus medullaris, L1-L2
(at birth, continuous from brain to L3)
collection of nerve roots in the lower lumbar, sacral, and coccygeal region
cauda equina
two sources of spinal cord blood supply
1) longitudinal oriented vessels
2) feeder arteries
longitudinal oriented vessels
arise superior to cervical portion of cord
feeder arteries AKA segmental spinal arteries
enter the canal through the intervertebral foramina at every level
what is the main artery of the spinal cord, branching from the segmental spinal artery?
artery of adamkiewicz
the segmental spinal arteries give rise to the ________ and _______ ___________ arteries and ___________ __________ arteries
anterior and posterior radicular arteries
(at every vertebral level)
segmental medullary arteries
this artery is the sole source of blood supply to the anterior spinal cord
anterior spinal artery
these two arteries originate from the cerebellar arteries and are located on each side of the spinal cord
posterior spinal arteries
interruption to blood supply of the anterior spinal artery will cause ________
(hint: supplies motor)
paraplegia
this artery is at the level of T10-L2 and supplies the lower anterior 2/3 of the spinal cord
artery of adamkiewicz
damage to the artery of adamkiewicz causes:
motor weakness
(anterior = motor)
the central area supplied by the anterior spinal artery is predominantly a _______ area
motor
contains processes of sensory neurons carrying information TO the CNS
posterior root
contains motor nerve fibers and carries signals AWAY from the CNS
anterior root
2 major branches of each spinal nerve:
posterior rami
anterior rami
all major _____ _____ are formed by the anterior rami
somatic plexus
innervate only intrinsic back muscles and a narrow strip of skin on the back
posterior rami
innervate other skeletal muscles of the body, including limbs and trunks, and most of the skin (except certain regions of the head)
anterior rami
supply the dura, ligaments, intervertebral discs, and blood vessels of the spinal cord
recurrent meningeal nerves
major somatic plexus (4):
cervical
BRACHIAL
lumbar
sacral
there are approximately ___ pairs of spinal nerves
31
number of cervical nerves
8
number of thoracic nerves
12
number of lumbar nerves
5
number of sacral nerves
5
number of coccygeal nerves
1
area of skin supplied by a single spinal cord level by a single spinal nerve
dermatome
autonomous region
where overlap of dermatomes is likely
level of umbilicus
T10
nipple level
T4
dermatome coincides with vertebral level at which:
spinal nerve originates
level of little finger
C8
procedure dermatome level: upper abdominal surgery
T4
procedure dermatome level: intestinal, gynecologic, and urologic surgery
T6
procedure dermatome level: vaginal delivery of a fetus, hip surgery
T10
procedure dermatome level: thigh surgery and lower leg amputations
L1
procedure dermatome level: foot and ankle surgery
L2
procedure dermatome level: perineal and anal surgery
S2 to S5 (SADDLE BLOCK)
(procedure dermatome level) Ex: C-section
T4 (intraabdominal)
(procedure dermatome level)
Ex: Inguinal hernia
T10 (lower abdomen)
(procedure dermatome level): surgery in the perineum
S2-S4
With central neuraxis analgesia/anesthesia techniques, sympathetic nerve conduction (vasomotor) is blocked. Why is the PNS spared?
nerve fibers (visceral afferent) lay outside the canal and are not exposed to LA
ATP PT MVP Motor
Autonomic temperature pain pressure touch motion vibration proprioception motor
a fibers
myelinated, large fibers with faster speed of impulse conduction
the larger the fiber the _____ to block
harder
a-alpha fibers are harder or easier to block than a-delta?
harder
the larger the fibers the faster or slower the speed of conduction?
faster
a-alpha fibers (hint: last to block)
motor & proprioception
a-beta fibers (hint: PT; M)
touch, pressure, small motor
a-gamma fibers (hint: PT)
pressure, touch
a-delta (hint: _TP)
sharp pain, heat/cold
B fibers
myelinated autonomic fibers in the preganglionic SNS
smallest and easiest to block
unmyelinated, postganglionic sympathetic fibers
c fibers
c fibers
smallest = first to get blocked
small, slow conduction
dull pain, temperature, touch
which fibers do you test to see if your block is working? how?
c fibers; pinprick (dull pain) or an alcohol swab (temperature)
level of sympathetic block is _____ dermatomes above the sensory level
2-3
blockade of ____ ______ _______ causes a VAGAL response
cardiac accelerator fibers
where are postganglionic fibers found?
in their target organs
where are preganglionic fibers found?
CNS
why are PNS nerve fibers RARELY affected by spinal or epidural blockade?
located OUTSIDE the subarachnoid space
paramedian sagittal TRANSVERSE view
“trident sign”
finger-like shadowing behind transverse processes
paramedian sagittal ARTICULAR process view
“camel humps”
paramedian sagittal LAMINAR view
“sawtooth” or “horse heads”
paramedian sagittal OBLIQUE view
slight medial tilt
optimizes view of posterior and anterior complexes
transverse INTERLAMINAR view
bat sign
articular processes/facet joints and transverse processes are visible
key ultrasonographic structures in the parasagittal TRANSVERSE process view (“trident sign”
erector spinae muscle, psoas muscle, transverse process
key ultrasonographic structures in the parasagittal ARTICULAR process view (“camel humps”
erector spinae muscle, articular processes
key ultrasonographic structures in the parasagittal OBLIQUE view (interlaminal)
laminae, POSTERIOR COMPLEX, INTRATHECAL SPACE, ANTERIOR COMPLEX
key ultrasonographic structures in the parasagittal of the transverse interlaminar (interspinous) view
anterior complex, posterior complex, midline interspinous ligament, articular processes, transverse processes
the ______ ______ is the MOST IMPORTANT ultrasonographic landmark
anterior complex
needle insertion and redirection should be guided by:
tactile feedback
(contact with bone, ‘feel’ of the ligamentum flavum, loss of resistance)
