A2 - protection of the CNS 3 Flashcards
how many spinal nerves does the vertebral column have?
31 pairs
how is the vertebral column divided?
cervical - 7
thoracic - 12
lumbar - 5
sacral - 5
coccygeal - 4 (fused)
what forms the vertebral arch?
the pedicals and laminae
functions of the vertebral column
- supports the body’s frame and connects the head to the rest of the body
- serves as protection for the spinal cord
- involved in posture and locomotion
- supports the weight of the body above the pelvis
describe the curvatures of the vertebral column
cervical
thoracic — primary
lumbar
sacral — primary
functions of vertebral curvatures
increase the strength of the vertebral column, its flexibility and its ability to absorb shock
what is a primary curvature?
concave anteriorly — thoracic and sacral
what are 3 abnormal curvatures?
- KYPHOSIS = an exaggerated thoracic curve. may result from osteoporosis
- LORDOSIS = an exaggerated lumbar curve. often seen in obesity and pregnancy
- SCOLIOSIS = an exaggerated lateral curve. most often seen in girls and may be associated with a. growth spurt
identify the parts of a typical vertebra
A = spinous process
B = lamina
C = vertebral foramen
D = transverse process
E = body
F = superior articular facet
G = pedicle
what are intervertebral discs?
- fibrocartilage pads that are sandwiched between adjacent vertebral bodies
- responsible for 25% the length of the vertebral column
where are iv discs not found?
C1-C2 and after S2
what are A and B?
A = nucleus pulposis — forms a gelatinous mass that is compromised of water, a few collagen fibres and some cartilage cells
B = annulus fibrosis — made of many sheets of fibrous connective tissues that are layered in rings around the nucleus pulposis
what are 3 functions of iv discs?
- increase size of vertebral column
- act as shock absorbers
- permit movement
describe cervical vertebrae and their distinct features
- 7
- have the smallest and thinnest intervertebral discs
- the most mobile
- have distinct features like : transverse foramina, 2 tubercles (anterior and posterior) and split (bifid) spinous processes, large, triangular vertebral foramen, small body
which cervical vertebrae are typical?
C3-C6
what do the transverse processes of cervical vertebrae end laterally in?
an anterior tubercle and a posterior tubercle — provide attachment for levator scapulae and scalenes
what is between the tubercles on the transverse processes of cervical vertebrae?
grooves for spinal nerves
describe the atlas (C1)
- consists of 2 arches (anterior and posterior) and contains 2 lateral masses
- has neither a body nor a spinous process
- the masses articulate with the occipital condyles of the skull, supporting its weight
- has a groove for the vertebral artery
describe the axis (C2)
- has an upward tooth-like projection (dens or odontoid process) and 2 superior articular facets
- it encircles both the dens and the spinal cord inside its coverings (meninges)
- it lies anterior to the spinal cord and serves as the pivot about which head rotation occurs
what does the dens of the axis articulate with?
the anterior arch of the atlas
what holds the dens in place against the anterior arch of the atlas?
the transverse ligament of the atlas
what cervical vertebra has the longest spinous process?
C7 = vertebra prominens
how is C7 atypical?
only transmit small accessory veins — thus the transverse foramina are smaller, and occasionally they are absent
what passes through the transverse foramina of the cervical vertebrae?
the vertebral arteries and their accompanying veins
describe thoracic vertebrae and their distinct features
- 12
- play a role in forming the thoracic cage
- contain several distinct features:
- costal facets — articulate with ribs
- heart-shaped vertebral bodies
- smaller vertebral foramina
- long and strong spinous and transverse processes which
point inferiorly
which thoracic vertebrae are typical?
T5-T8
demi facets vs costal facets
demi-facets : on the sides of each vertebral body. these articulate with the heads of the ribs
costal facets : on transverse processes. these articulate with the tubercles of ribs. only present on T1-T10
what do atypical thoracic vertebrae bear? explain
= whole costal facets instead of demifacets
> the superior costal facets of T1 aren’t demifacets because there are no demifacets on the C7 vertebra above and rib 1 articulates with only T1
T1 has a typical inferior costal (demi) facet
T10 has only one bilateral pair of whole costal facets located partly on its body and partly on its pedicle
T11 and T12 also have only a single pair of whole costal facets, located on their pedicles
there is no articulation between T11 and T12 with their ribs
what are the distinct lumbar vertebrae features?
- large, kidney shaped body
- quadrangular spinous processes
- triangular vertebral foramen
- long, slender transverse processes
- larger grey matter
why are lumbar vertebrae the largest in the body?
facilitate weight-bearing
what are the laminae and pedicels like in lumbar vertebrae/
thick and strong
what are the lumbar spinous processes like?
short and sturdy for the attachment of strong lumbar muscles
what is the largest vertebrae of the entire body and what does it do?
L5
- supports and transmits body weight to the base of the sacrum
where does the spinal cord terminate?
conus medullaris — L1/L2
describe the sacrum
- 5
- fused
- main role is to transmit the entire wight of the upper body to the pelvis in order to reach the lower limbs
- has a base, apex, and 3 surfaces (pelvic, posterior and lateral)
- sacral canal in middle = continuation of spinal canal
what does the sacral canal contain?
cauda equina of spinal cord
what do sacral foramina do?
allow for the exit of the spinal nerves
what are sacral crests (median, intermediate, lateral)?
represent the fused processes of the sacral vertebra
describe the coccyx
- 4
- 2 surfaces: pelvic and posterior
- short transverse processes
- point of attachment for the gluteus maximus and coccygeal muscles
why does the ability of iv discs to absorb shock decrease as a person ages and why are they more likely to tear?
the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, and the annulus becomes weaker
what is a prolapsed disc?
when the nucleus pulposus is forced out of the disc
what are the iv symphases (discs)?
secondary cartilaginous (symphyses)
what are cervical vertebrae also connected by?
uncovertebral joints (clefts of Luschka)
what are the vertebral bodies and iv discs reinforced by?
2 fibrous, longitudinal ligaments = anterior and posterior longitudinal ligaments
describe the anterior longitudinal ligament
- extends along the anterior surface of the bodies of the vertebrae, from skull to sacrum
- runs entire length of vertebral column
- thicker and stronger than posterior
what are the functions of the anterior longitudinal ligament?
- maintains stability of the joints
- prevents hyperextending of the vertebral column
describe the posterior longitudinal ligament
- runs along the anterior aspect of the vertebral canal from skull to sacrum
- it is attached to the posterior borders of the IV discs
- it is narrow where is overlies each body, and widens out to cover the back of each disc
- helps in a small way to limit flexion of the vertebral column
what do the anterior and posterior longitudinal ligaments look like?
what are adjacent vertebral arches connected by?
synovial joints called zygapophyseal (facet) joints
describe the zygapophyseal (facet) joints
- only synovial joints of the spine
- formed between superior and inferior articular facets
- facilitate flexion and extension in the cervical and thoracic spines
- also permit rotational movements in the thoracic spine
what accessory ligaments are vertebral arches strengthened by?
- ligamenta flava
- interspinous ligaments
- nuchal ligament
- supraspinous ligament
describe ligamentum flavum
- connects adjacent laminae
- prevent separation of lamina during sudden flexion of the vertebral column
describe interspinous ligaments
connects adjacent spinous processes
describe nuchal ligament
extends from the skull (occipital protuberance and posterior border of foramen magnum) to the spinous processes of C7 where it merges with the supraspinous ligament
describe supraspinous ligament
a long band that connects the tips of spinous processes (from C7 to sacrum)
identify A, B and C
A = intertransverse
B = supraspinous
C = interspinous
name A and B
A = anterior longitudinal
B = posterior longitudinal
name the 2 craniovertebral joints formed between the skull and the atypical vertebrae of the cervical spine
- atlanto-occipital
- atlanto-axial
descirbe the atlanto-occipital joint
- a pair
- formed between the lateral masses of the atlas (C1) and the occipital condyles of the cranium
- permit flexion, extension, and sideways tilting of the head
= SYNOVIAL ARTICULATIONS BETWEEN THE OCCIPITAL CONDYLES AND SUPERIOR FACETS OF C1
describe the atlanto-axial joint
- 2 lateral, 1 median
- located between the C1 and C2 vertebrae
- facilitate pivot motion of the head (as in a disapproving stroke)
= SYNOVIAL ARTICULATIONS BETWEEN THE DENS AND LATERAL MASSES OF C2 WITH THE ANTERIOR ARCH AND LATERAL MASSES OF C1
what is the anterior atlanto-occipital membrane?
continuation of the anterior longitudinal ligament, connects the anterior arch of atlas with anterior margin of the foramen magnum
what is the intertransverse ligament?
runs between adjacent transverse prcoesses
what is the alar ligament?
connects the dens to the medial sides of the occipital condyles
what is the cruciate ligament?
consists of a transverse part that binds the odontoid process to the arch of the atlas and a vertical part that binds the posterior aspect of the body of the atlas to the anterior margin of the foramen magnum
what is the apical ligament?
a median placed ligament that connects the apex of the dens to the anterior margin of the foramen magnum
what is the membrane tectora?
- upward continuation of the posterior longitudinal ligament
- covers the posterior surface of the odontoid process and attaches to the occipital bone
what are spinal nerves formed from?
the dorsal and ventral roots of the spinal cord
where do spinal nerves exit the vertebral column?
through the intervertebral foramina
where do the roots of the 1st spinal nerve exit?
between C1 and the occipital bone
name A, B and C and where they arise
A = femoral nerve — L2-L4
B = obturator nerve — L2-L4
C = sciatic nerve — L4-S3
what supplies the anterior compartment of the thigh?
femoral nerve
what supplies the medial compartment of the thigh?
obturator nerve
what is the largest nerve in the body?
sciatic nerve
what is the route of the sciatic nerve?
- formed from ventral rami of L4-S3
- exits the greater sciatic foramen
- enters the buttock from under piriformis muscle
- lies deep to gluteus maximus
- crosses ischial tuberosity, descends on obturator internus, gemelli and guadriceps femoris
- lies deep to hamstrings and is crossed by long head of biceps
- bifurcates into tibial and common perineal nerves
name 4 nerve plexuses and their roots
- cervical : C1-C5
- brachial : C5-T1
- lumbar : L1-L4
- sacral : L4-S4
describe the ventral root of a spinal nerve
- contains efferent nerve fibres
- carry stimuli from CNS to target structures
describe the dorsal root of a spinal nerve
- contains afferent nerve fibres
- return sensory info from the trunk and limbs to the CNS
what forms a nerve plexus?
the anterior rami
what are rami communicantes responsible for?
relaying autonomic signals between the spinal nerves and the sympathetic trunk
grey vs white ramus communicans
- spinal nerves can have a grey ramus communicans and a white ramus communicans
> grey — exist at all levels of the spinal cord
— carry postganglionic nerve fibres from the
paravertebral ganglia in the sympathetic chain to their
target organ
> white — only exit the spinal cord between the levels of T1-L2
— carry preganglionic nerve fibres from the spinal cord
to the partavertebral ganglia in the sympathetic chain
what is the meningeal branch given off by spinal nerves?
provides sensory and vasomotor innervation to the spinal meninges
what is myelin in the CNS produced by?
oligodendrocytes
what is myelin in the PNS produced by?
Schwann cells
is dorsal sensory or motor? ventral?
dorsal = sensory
ventral = motor
describe somatic efferent fibres
- originate in the ventral column of central grey matter in the spinal cord
- pass through the anterior root of the spinal nerve
- responsible for motor innervation of the skeletal muscles
describe somatic afferent fibres
- carry sensory information from the skin, joints and muscle to the posterior/dorsal column of grey matter in the spinal cord
- these fibres pass through the dorsal root ganglion
describe visceral efferent fibres
- autonomic fibres that supply the organs
- divided into sympathetic and parasympathetic fibres
- sympathetic fibres originate from the thoracic spinal nerves as well as L1 and L2
- parasympathetic nerves come from the S2, S3, S4 spinal nerves only to supply the pelvic and lower abdominal viscera
- the remainder of PS nerves come from extensions of the cranial nerves into the thoracic and abdominal cavities
describe visceral afferent fibres
carry sensory info through the dorsal root ganglion and to the dorsal column of grey matter in the spinal cord
what do somatic efferent fibres innervates?
skeletal muscles
what do somatic afferent fibres innervate?
skin, joints and muscles
what are dermatomes?
- sensory nerve fibres that innervate a segment of skin
- associated with a single spinal cord level
what are myotomes?
similar in function to dermatomes, but carry motor stimuli. they are responsible for segmental innervation of skeletal muscle
what is the blood supply of the anterior aspect of the spinal cord provided by?
the anterior spinal artery
what does the anterior spinal artery run in?
anterior median fissure
what does the anterior spinal artery arise from?
vertebral artery
what do the 2 posterior spinal arteries arise from?
either the vertebral artery or the posterior inferior cerebellar artery
where do radicular arteries enter the vertebral canal?
through iv foramina
what does the spinal cord’s venous drainage consist of?
3 anterior and 3 posterior spinal veins, which drain into radicular veins, which then empty into the internal vertebral venous plexus
what are anterior and posterior spinal arteries branches of in the thoracic section of the spinal cord?
the posterior intercostal artery
what is the thecal/dural sac and what does it contain?
- the membranous sheath of dura mater that surrounds the spinal cord and the cauda equina
- contains CSF in which the spinal cord ‘floats’
grey matter vs white matter
- grey matter is where synapses between neurones occur — dendrites and terminal axons of neurones
- white matter is where neurones travel through — contains axons
where is a sensory neurons body located?
spinal sensory ganglion
what forms a spinal nerve?
dorsal and ventral root
laminas de rexed
— certain neurons in certain places
The needle in a lumbar puncture is usually inserted between the L3 and L4 (or L4 and L5) vertebrae. The spinous process of L4 is determined by a plane that transects the highest points of the iliac crests.
what is the name of this plane?
supracristal plane
what is is formed by the superior notch on the pedicle of one vertebra and the inferior notch on the pedicle of an adjacent vertebra?
intervertebral foramen
An exaggerated sagittal curvature in the thoracic region is known what?
a kyphosis
what direction to the superior articular facets face in the lumbar region?
medially
what direction do the inferior articular facets face in the cervical region?
anteriorly and inferiorly
in what vertebra are the pedicles strong and directed backwards?
lumbar
in what vertebra do the inferior articular facets face anteriorly and medially?
thoracic
in what vertebra do the superior articular facets face posteriorly and laterally?
thoracic
where do the inferior articular facets face laterally?
lumbar vertebra
What type of synovial joint is the atlanto-occipital joint?
condyloid
The anterior atlanto-occipital membrane connects the anterior arch of the atlas to the anterior margin of which structure?
foramen magnum
What type of synovial joints are the lateral atlanto-axial joints?
What type of synovial joint is the medial atlanto-occipital joint?
- plane
- pivot
what are the 2 lateral atlanto-axial joints located between?
superior facets of axis and inferior facets of atlas
Which type of cartilage covers the articulating surfaces of the vertebral bodies?
hyaline
Lesley’s prolapsed disc was at L5/S1 - on which nerve would this prolapsed disc impinge?
S1
What is the name used for the connective tissue that surrounds the spinal nerve?
epineurium
Where does venous blood from the spinal cord drain to?
internal vertebral plexus, which in turn drains into the external vertebral plexus
Where is the internal venous plexus located?
epidural space of vertebral canal
What type of neurone does a sympathetic ganglion contain?
multipolar
What type of neurone does the dorsal root ganglion contain?
unipolar
