Back, Vertebral Column, and Spinal Cord (Week 1--Miller/Stark)

Question 1

Extrinsic “back” muscles

Answer 1

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

Question 2

Intrinsic back muscles (deep, or true)

Answer 2

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

Question 3

Vertebral column

Answer 3

33 vertebrae total

7 cervical

12 thoracic

5 lumbar

5 sacral (fused into 1 bone)

4 coccygeal

Question 4

Primary versus secondary curvature

Answer 4

Primary (developed before birth): thoracic and sacrococcygeal

Secondary (developed during infancy): cervical and lumbar

Question 5

Zygapophyseal (facet) joints

Answer 5

Synovial joints between articular processes of adjacent vertebrae

Permit gliding movements between vertebrae

Innervated by dorsal rami

Question 6

Intervertebral discs

Answer 6

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

Question 7

Intervertebral (neural) foramen

Answer 7

Foramen between two adjacent articulating vertebrae

Where short spinal nerve is before it branches into dorsal and ventral ramus nerves

Question 8

Vertebral canal

Answer 8

Formed by vertebral foramen of articulating vertebrae

Location for spinal cord and meninges

Question 9

Ligaments of vertebral column from anterior to posterior

Answer 9

1) Anterior longitudinal ligament
2) Posterior longitudinal ligament
3) Ligamentum flavum
4) Interspinous ligament
5) Supraspinous ligament

Question 10

Movements of vertebral column are greatest where?

Answer 10

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

Question 11

How many pairs of spinal nerves do we have?

Answer 11

31

Question 12

3 membranes (meninges) and spaces between them

Answer 12

Epidural space

Dura mater

Subdural space

Arachnoid mater

Subarachnoid space (contains CSF)

Pia mater

Spinal cord

Question 13

Denticulate ligament

Answer 13

Formed of pia mater

Serrated ligament between dorsal and ventral roots that helps anchor spinal cord within dural sac

Question 14

Dorsal versus ventral roots of spinal nerves

Answer 14

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

Question 15

Dorsal versus ventral rami nerves

Answer 15

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

Question 16

Spinal cord segmentation

Answer 16

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)

Question 17

Where does the spinal cord end?

Answer 17

Spinal cord ends at L2

Spinal cord is much shorter than vertebral column!

Question 18

Filum terminale

Answer 18

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

Question 19

Where do the dural sac and subarachnoid space end?

Answer 19

S2

Question 20

Conus medullaris

Answer 20

When spinal cord ends, tapers down to form cone-like structure called conus medullaris which ends at L2

Question 21

Cauda equina

Answer 21

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

Question 22

Arteries of spinal cord

Answer 22

1 anterior spinal artery

2 posterior spinal arteries

Question 23

Internal vertebral venous plexus

Answer 23

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

Question 24

Thoracolumbar fascia

Answer 24

Dense connective tissue that surrounds and covers deep/true back muscles

Question 25

Scoliosis

Answer 25

Abnormal lateral curvature of spine

May be congenital or secondary to disc herniation

Question 26

Kyphosis

Answer 26

Abnormally pronounced thoracic primary curvature

Osteoporosis and degeneration of intervertral discs can lead to senile kyphosis

Question 27

Distinguishing features of cervical, thoracic and lumbar vertebrae

Answer 27

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

Question 28

C1 vertebrae (Atlas)

Answer 28

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

Question 29

C2 vertebrae (Axis)

Answer 29

Articulates superiorly with C1 and inferiorly with C3

Has odontoid process (dens) which is the “axis” around which the atlas (C1) rotates

Question 30

Alanto-occipital joint

Answer 30

Allows for head flexion and extension (nodding “yes”)

Condyloid process of occipital bone on superior articular facet of C1 (atlas)

Question 31

Median alantoaxial joint

Answer 31

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

Question 32

Sacrum

Answer 32

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)

Question 33

Caudal anesthesia

Answer 33

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

Question 34

Why is L4 spinous process important and how do you find it?

Answer 34

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

Question 35

Characteristics of synovial joints

Answer 35

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

Question 36

Characteristics of cartilaginous joints

Answer 36

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

Question 37

Herniated disc

Answer 37

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

Question 38

Osteophytes

Answer 38

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

Question 39

According to anatomical classification, what are 3 types of joints?

Answer 39

1) Cartilaginous joints
2) Fibrous joints
3) Synovial joints

Question 40

Which are the atypical vertebrae?

Answer 40

C1 (atlas)

C2 (axis)

Sacrum

Coccyx

Question 41

Are the spinal nerve, dorsal ramus, ventral ramus sensory or motor nerves?

Answer 41

They are all mixed nerves–contain both sensory and motor fibers

Question 42

Dorsal ramus cutaneous nerves

Answer 42

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