Back, Vertebral Column, and Spinal Cord (Week 1--Miller/Stark) Flashcards
Extrinsic “back” muscles
Not true back muscles!
Ventral rami innervation
Superficial layer (connect upper limbs to trunk and control limb movements): trapezius, latissimus dorsi, rhomboids, levator scapulae
Intermediate layer: serratus posterior superior, serratus posterior inferior
Intrinsic back muscles (deep, or true)
Deep, or true back muscles!
Dorsal rami innervation
Blood supply (except to splenius muscles) is from dorsal branches of posterior intercostal arteries
Superficial layer: splenius muscles = splenius capitis, splenius cervicis
Intermediate layer: erector spinae muscles = iliocostalis, longissimus, spinalis (note: these can be subdivided into 3 groups but we don’t have to know those)
Deep layer: transversospinalis muscles = semispinalis, multifidus, rotatores, interspinous and intertransverse
Collectively, superficial, intermediate, and deep muscles all called paraspinals
Vertebral column
33 vertebrae total
7 cervical
12 thoracic
5 lumbar
5 sacral (fused into 1 bone)
4 coccygeal
Primary versus secondary curvature
Primary (developed before birth): thoracic and sacrococcygeal
Secondary (developed during infancy): cervical and lumbar
Zygapophyseal (facet) joints
Synovial joints between articular processes of adjacent vertebrae
Permit gliding movements between vertebrae
Innervated by dorsal rami
Intervertebral discs
Fibrocartilagenous intervertebral discs/joints between adjacent vertebral bodies are for weight bearing and strength
Outer, tough anulus fibrosus (strength)
Inner, gelatinous nucleus pulposus (shock absorption during weight bearing)
This subtype of cartilaginous joins it called symphysis (symphyseal joint)
Discs play major role in development of curvatures of vertebral column
Intervertebral (neural) foramen
Foramen between two adjacent articulating vertebrae
Where short spinal nerve is before it branches into dorsal and ventral ramus nerves
Vertebral canal
Formed by vertebral foramen of articulating vertebrae
Location for spinal cord and meninges
Ligaments of vertebral column from anterior to posterior
1) Anterior longitudinal ligament
2) Posterior longitudinal ligament
3) Ligamentum flavum
4) Interspinous ligament
5) Supraspinous ligament
Movements of vertebral column are greatest where?
Flexion is greatest in cervical region
Extension is greatest in lumbar region
Lateral bending is greatest in lumbar region
Rotation is greatest in thoracic region
How many pairs of spinal nerves do we have?
31
3 membranes (meninges) and spaces between them
Epidural space
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space (contains CSF)
Pia mater
Spinal cord
Denticulate ligament
Formed of pia mater
Serrated ligament between dorsal and ventral roots that helps anchor spinal cord within dural sac
Dorsal versus ventral roots of spinal nerves
Dorsal root: sensory fibers coming into spinal cord; has DRG along dorsal root that contains sensory cell bodies
Ventral root: motor fibers leaving spinal cord; cell bodies for motor fibers are in ventral horn of gray matter in spinal cord
Dorsal versus ventral rami nerves
Spinal nerve splits into two branches–dorsal ramus nerve and ventral ramus nerve
Dorsal rami nerves: innervate intrinsic or true back muscles on posterior 1/3 of body wall
Ventral rami nerves: innervate antero-lateral 2/3 of body wall
Spinal cord segmentation
8 cervical (C1-8 come out ABOVE corresponding vertebrae)
12 thoracic (T1-12)
5 lumbar (L1-5)
5 sacral (S1-5)
1 coccygeal (Co1, which is end of spinal cord)
Where does the spinal cord end?
Spinal cord ends at L2
Spinal cord is much shorter than vertebral column!
Filum terminale
Ligament-like structure formed by pia mater
Extends inferiorly from conus medullaris to anchor to coccyx along with dura mater and arachnoid mater to form coccygeal ligament
Helps provide stability for spinal cord
Where do the dural sac and subarachnoid space end?
S2
Conus medullaris
When spinal cord ends, tapers down to form cone-like structure called conus medullaris which ends at L2
Cauda equina
Dorsal and ventral roots proceeding inferiorly (have to, in order to get below corresponding vertebrae) surround the conus medullaris and look like horse’s tail so called cauda equina
Arteries of spinal cord
1 anterior spinal artery
2 posterior spinal arteries
Internal vertebral venous plexus
AKA Bateson’s Plexus
Veins draining spinal cord and vertebrae form internal vertebral venous plexus which is a network of valveless veins continuous with cranial dural venus sinuses within skull
Located in epidural space (although other blood vessles are with spinal cord deep to pia mater)
Pathway for infection between head and lower parts of body! Carcinoma of prostate may metastasize to cranial cavity this way
Thoracolumbar fascia
Dense connective tissue that surrounds and covers deep/true back muscles
Scoliosis
Abnormal lateral curvature of spine
May be congenital or secondary to disc herniation
Kyphosis
Abnormally pronounced thoracic primary curvature
Osteoporosis and degeneration of intervertral discs can lead to senile kyphosis
Distinguishing features of cervical, thoracic and lumbar vertebrae
Cervical vertebrae: bifid spinous process; transverse foramen (for vertebral artery)
Thoracic vertebrae: costal and demifacets (for ribs); inferiorly oriented spinous processes
Lumbar vertebrae: lack costal facets; have quadrangular and horizontally oriented spinous processes; are chubby/chunky
C1 vertebrae (Atlas)
Articulates superiorly with cranuim (occipital bone)
Has no body and no spinous process (just has anterior and posterior arch)
Transverse ligament holds dens of C2 in place
Large superior articular facets articulate with condyloid processes of occipital bone
C2 vertebrae (Axis)
Articulates superiorly with C1 and inferiorly with C3
Has odontoid process (dens) which is the “axis” around which the atlas (C1) rotates
Alanto-occipital joint
Allows for head flexion and extension (nodding “yes”)
Condyloid process of occipital bone on superior articular facet of C1 (atlas)
Median alantoaxial joint
Allows for rotation of the head (shaking “no”)
Rotation of C1 (atlas) around dens of C2 (axis)
Note: no intervertebral disc between atlas and axis
Sacrum
Fusion of 5 bones (S1-5 vertebrae)
Anterior: can see body of S1, ala (wings), promontory, anterior sacral foramina (transmits ventral rami of S1-5 spinal nerves)
Posterior: can see sacral canal, sacral hiatus, posterior sacral foramina (transmits dorsal rami of S1-5 spinal nerves)
Caudal anesthesia
Obstetricians use this methos of nerve block to relieve labor pain (1st and 2nd stage)
May be administered through sacral hiatus, and solutions pass superiorly in loose connective tissue and bathe spinal nerves as they emerge from dural sheath
Why is L4 spinous process important and how do you find it?
L4 spinous process is important because is landmark in doing lumbar punctures to sample CSF
Horizontal line drawn across iliac crests intersects L4 spinous process
Characteristics of synovial joints
Synovial joints also called diarthroses, and are considered highly movable joints
1) Fibrous joint capsule encloses joint cavity
2) Synovial membrane lines inside of fibrous capsule
3) Synovial fluid is secreted by synovial membrane
4) Hyaline cartilage caps ends of articulating bones
Characteristics of cartilaginous joints
Two bones separated by cartilage of some type
Two kinds of cartilagenous joints are symphyses and synchondroses
Symphyseal joints mostly in midline of body and are slightly moveable
Herniated disc
Nucleus pulposus herniates through weakened annulus fibrosus
Can endanger spinal cord, dorsal/ventral roots of spinal nerve, dorsal root ganglion (sensory cell bodies), spinal nerve
Herniations more likely to occur in posterolateral direction
Sensory pain may be distributed along associated dermatome; affected motor fibers can cause muscle weakness; compromised disc may cause vertebral column to appear scoliotic
Osteophytes
Bony spur-like growth on vertebral bodies
Osteoarthritic formation of osteophytes can narrow intervertebral foramen and impinge on spinal nerve and/or spinal nerve roots
According to anatomical classification, what are 3 types of joints?
1) Cartilaginous joints
2) Fibrous joints
3) Synovial joints
Which are the atypical vertebrae?
C1 (atlas)
C2 (axis)
Sacrum
Coccyx
Are the spinal nerve, dorsal ramus, ventral ramus sensory or motor nerves?
They are all mixed nerves–contain both sensory and motor fibers
Dorsal ramus cutaneous nerves
Innervate true, deep back muscles
Pierce superficial “back” muscles without innervating them and then innervate skin of the back on posterior 1/3 of body wall circumference
