The Spinal Cord Flashcards
How long and how wide is the spinal cord?
18 inches long and 1/2 inch wide
Where does CNS tissue (spinal cord) end?
between vertebrae L1 and L2
Conus medullaris
termination of spinal cord
thecal (dural) sac
membranous sheath tube of dura mater that surrounds the spinal cord and the cauda equina. contains CSF which provides nutrients and buoyancy to the spinal cord.
Where does the thecal sac end?
S2
Name the meninges
Dura Mater
Arachnoid Mater
Pia Mater
Arachnoid Mater
delicate membrane made of fibrous and elastic tissue that lines the dural sac and the dural root sleeves. Encloses the CSF-filled subarachnoid space containing the spinal cord, spinal nerve roots, and spinal ganglia. It is held against the dura but separable from it.
Lumbar cistern
the subarachnoid space in the lower lumbar spinal canal. It is an enlargement of the subarachnoid space in the dural sac, distal to the conus medullaris. It contains CSF and the nerve roots of the cauda equina.
Pia Mater
innermost covering membrane of the spinal cord. Closely follows the entire spinal cord and directly covers the roots of spinal nerves and the spinal blood vessels. Inferior to the conus medullaris, the pia continues as the filum terminale.
Denticulate ligaments
specializations of pia mater. Form separate dorsal and ventral rootlets. Extend laterally from cord and attaches to the dura by way of 21 pairs of denticulations, they suspend the spinal cord in the subarachnoid space.
How many pairs of spinal nerves are there?
31 pairs
Spinal Nerves
contain both sensory and motor axons identified by the first letter of the spinal cord part and number.
How many cervical nerves are there?
8 cervical nerves even though there are 7 cervical vertebrae. Starts above each vertebra. Nerve C8 is above T1.
How many thoracic nerves are there?
12
How many lumbar nerves are there?
5
How many sacral nerves are there?
5
How many coccygeal nerves are there?
1
Spinal nerves pass through the
intervertebral foramen
Intervertebral foramen
opening between the pedicles of the adjacent vertebra. It is the opening for the passage of the spinal nerves out from the spinal cord.
Intervertebral Disc
- fibrocartilaginous joint of the motion segment
- make up 1/4 length of the spinal column
- present at levels C2-C3 to L5-S1
- Allows compressive, tensile, and rotational motion
- largest avascular structures in the body
Annulus Fibrosis
- outer portion of the intervertebral disc
- made up of lamellae
- great tensile strength
Lamellae
- layers of collagen fibers
- arranged obliquely 30 degrees
- reversed contiguous layers
The intervertebral disc is made up of
Annulus Fibrosis
Nucleus Pulposus
Nucleus Pulposus
- inner structure of the intervertebral disc
- gelatinous
- high water content
- resists axial forces
Blood supply to the intervertebral disc
- intervertebral discs have no significant vascular structures
- they receive their blood supply by diffusion through the vertebral body endplates
- a network of vessels located centrally in the endplate allows nutrients to diffuse into the nucleus pulposus and annulus fibrosis.
Anterior longitudinal ligament
the ligament that runs from superior to inferior along the anterior surface of the body of the vertebrae. It helps attach the bodies of the vertebrae to each other
Posterior longitudinal ligament
- weaker than anterior
- runs from the axis (C2) caudally to the sacrum
- narrow at the levels of the vertebrae, but the fibers extend laterally at the disc level
The attachment of the posterior longitudinal ligament to the intervertebral disc helps…
to reinforce the posterior aspect of the annulus fibrosis. However, because the ligament thins laterally, most disc herniations occur in a posterolateral direction.
The _______ _______ connects each adjacent spinous process.
interspinous ligament
In the cervical spine, the interspinous ligament becomes part of the ______ _______, which extends cranially to insert into the occiput.
ligamentum nuchae
The _____ _____ is a very strong band connecting the tips of contiguous spinous processes. It extends from C7 to the sacrum. Above C77 these fibers are part of the ligamentum nuchae.
supraspinous ligament
Ligamentum flavum
- also known as the yellow ligament
- consists of elastic fibers oriented vertically that extend from the anterior inferior surface of the lamina above to the superior posterior surface of the lamina below
- tends to thicken as it progresses down the spine, beginning at the axis (C2) and extending to the sacrum
Lumbar Puncture travels through
skin, subcutaenous layer, back muscles, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, dura mater, arachnoid mater, and into the subarachnoid space where there is CSF.
The nucleus pulposus is a _______ structure, not liquid.
cargilaginous
______ _____ act as shock absorbers between the vertebral bodies.
intervertebral discs
Where is there no intervertebral disc found?
between the C1 and C2, and between L5 and S1
Intervertebral discs are _____ joints.
cartilagenous
Is the intervertebral disc penetrated to perform a spinal tap?
no, only the subarachnoid space is needed.
Herniated disc
- herniation of the nucleus pulposis through a weakened anulus fibrosis, usually posterolaterally
- commonly puts pressure on the nerve roots or dorsal root ganglion exiting the intervertebral foramen at or below this level, leading to the symptoms of a “slipped disc”; these occur most frequently in the cervical and lumbar regions due to these segments being the most mobile
If a herniated disk presses the nerve between the C5 and C6 vertebrae, it will be compressing the ____ nerve, which emerges above the ____ vertebra.
C6; C6
If a disc herniates in the lumbar region, ex. between L5 and S1, it will be affecting the _____ spinal nerve.
S1; this is because the L5 nerve lies immediately below the L5 pedicle, above the herniating disc and is not affected. However, the S1 nerve roots are already proceeding laterally toward the S1 intervertebral foramen, so it is usually caught by the herniating L50S1 disc.
pseudounipolar neurons are (sensory/motor)?
sensory (afferent)
multipolar neurons are (sensory/motor)?
motor (efferent)
The ____ _____ _____ supplies sensory innervation to the skin of the back and motor innervation to the true back muscles.
dorsal primary ramus
Which muscles are considered true muscles of the back and why?
Intrinsic (Erector spinae, suboccipital, and splenius) muscles. Primary function is to produce movements of the vertebral column.
Extrinsic back muscles
- lie most superficially on the back
- muscles of the upper limb that have migrated to the back during fetal development
- divided into superficial and intermediate
Superficial extrinsic back muscles
Trapezius, rhomboid major & minor, Latissimus dorsi, levator scapulae
intermediate extrinsic back muscles
serratus posterior inferior and serratus posterior superior
Intrinsic back muscles movements
- flexion (touching toes)
- extension (bending backward)
- lateral bending
- rotation (head and neck or entire torso)
Ventral rami of C1-T1 and T12-S5 contribute to the formation of:
plexuses
ventral rami of T2-T11 continue as
intercostal nerves
Dermatome
the area of skin innervated by the cutaneous branches of a single spinal nerve
CSF function
- colorless fluid that occupies the subarachnoid space surrounding the brain, spinal cord, and ventricular system
- provides mechanical and immunological protection for the brain, spinal cord, and thecal sac
CSF production
-produced by the choroid plexus in the third, fourth, and lateral ventricles of the brain.
CSF is an ultrafiltrate of ____ ____ through the permeable capillaries of the choroid plexus.
blood plasma
how much CSF is formed each day?
~500 mL per day; total amount turned over 3-4 times per day
