Anatomy of Spinal Regions, Spinal Cord and Meninges
I. Curvatures of the Vertebral Column [N.142]
Early embryo, vertebral column is C-shaped
A. Normal
1. Primary curvatures:
Posterior convexities present at birth
Immobile: attach. to skeletal components (rib cage and pelvis)
Thoracic and Sacral
2. Secondary curvatures:
Anterior convexities that develop after birth
Flexible: lack of skeletal connections
Cervical (child hold head erect) and Lumbar (child stand erect/walk)
B. Abnormal
1. Kyphosis
Exaggerated posterior curvature
Thoracic region
“hump-back”
Related to oseoporosis
2. Lordosis
Exaggerated anterior curvature
Lumbar region
“sway-back”
obesity, pendulous abdomen, pregnancy
3. Scoliosis
Lateral curvature
Most common, 0.05% of population
From unequal growth of two sides of vertebrae
II. Regional Characteristics of Vertebrae
Function: protects the spinal chord, supports body weight, axis for body, pivot for head, posture, and locomotion
33 vertabrae, 5 regions
lumbar and sacral regions carry more weight (larger)
cervical, thoracic, and lumbar vertebrae articulate at intervertebral joints- flexibility
vertebral bodies ¾ of length, intervertebral discs ¼ of length of vertebral column
# cervical vertebra constant, numerical variations in thoracic, lumbar and sacral in %5
A. Cervical C1 and C2 [N.12]
moveable
C1- atlas
concave superior articular facets for occipital condyles
posteiro tubercle-no spinus process
no body
anterior arch that bears facet for dens and posterior arch
carries full skull
rotates on C2
C2- axis
Strongest cervical vertebra
Dens (odontoid process)-projects superiorly from body
B. Cervical C3-C7 [N.13]
moveable
Vertebral foramen- large and triangular
Spinous Processes- C3-C5-short and bifid
C6- long
C7- longer (vertebra prominens)
C. Thoracic T1-T10 [N.143]
Moveable
Vertebral foramen- circular
Body- heart-shaped
Spinous processes- long, slender, directed downward
Costal facets- for articulation with ribs
Facet on vertebral body- articulation with head of rib
Facet on transverse process- articulation with tubercle of rib
D. Lumbar L1-L5 [N.144]
Vertebral foramen – vary from oval to triangular
Bodies- kidney-shaped
Spinus Processes-oblong and stubby
Massive bodies lacking costal facets
E. Sacral S1-S5 [N.145]
Fused into wedge shape
Transmits weight of body to pelvic girdle via saroiliac joints
Anterior surface-smooth and concave
Posterior surface- arches, rough and convex, marked by medial sacral crest formed from fused spinous processes
Sacral Foramen- anterior and posterior, spinal nerve rami emerge here
Sacral Promontory- anterior projection of S1- obstetric landmark
S4 and S5- lacks spinou sprocess
Sacral hiatus- bony channel allows hypodermic needle access to inferior vertebral canal
F. Coccygeal 4 [N.145]
Fused
Bodies only- no arches or processes
Non-weight bearing coccyx or “tail bone”
Provides attachment for pelvic muscles and ligaments
III. Anthrology
Secondary cartilaginous joints (intervertebral discs) [M.193]
Attachment between bodies of adjacent vertebrae C2-S1
Major role in weight bearing
Symphsis joint: annulus fibrosus surrounding nucleus pulposus
Annulus fibrosus-concentric layers of fibrocartilage that inserts into articular surface of adjacent vertebral bodies
Nucleus pulposis- gelatinous, highly elastic, high water content (shock absorber), avasular (nutrients from diffusion)
Synovial joints
Articular surfaces covered by hyaline cartilage
Loose fibrous capsule surrounds juncture
Zygapophyseal (facet) joints
Four per verbetra
Synovial joints that lie between articular processes
Permit gliding movements between vertebrae
Atlanto-occipital joints
Synovial joints between superior articular facets of atlas and occipital condyles of skull
Facilitate nodding of head
Atlantoaxial joints
Synovial joint- two lateral and one median (dens)
Dens of axis articulates with anterior arch of atlas
Facilitates pivoting of head
Fibrous Joints (vertebral ligaments)
Anterior longitudinal ligament
Broad, fibrous band that runs along anterior surface of vertebral bodies and intervertebral discs
From occipital bone to anterior surface of sacrum
Maintains stability of joints between vertebral bodies
Prevents hyper extension of vertebral column
Posterior longitudinal ligament
Narrow fibrous band that runs along posterior surface of vertebral bodies and intervertebral discs within vertebral canal
From skull to sacrum
Prevents hyperflextion of vertebral column
Ligamenta flava
Short , broad elastic bands that run between laminae of adjacent vertebrae
Consists of elastic tissue
Help to maintain normal posture and spinal curvatures
Interspinous ligaments
Small ligaments that span distance between adjacent spinous processes
Relatively weak
Supraspinous ligaments
Strong, cord-like ligament runs along tips of spinous processes
Ligamentum nuchae
Thickened supraspinous ligament of superior vertebral column
Forms triangular median septum between muscles on each side of posterior neck
Intertransverse ligaments
Run between adjacent transverse processes
Substantial only in lumbar region.
IV. Spinal Cord
[N.149]
Spinal cord segments situated within vertebral canal at level superior to corresponding vertebra.
Spinal nerve roots (dorsal and ventral) emerge from spinal cord segments, and descend within the vertebral canal, and merge within intervertebral foramen to form mixed spinal nerves.
Mixed spinal nerves exit vertebral canal
Cervical region- above corresponding vertebra
Thoracic, Lumbar, Sacral regions- below corresponding vertebra
A. External Structure [N.149 and N.151]
From foramen magnum of occipital bone to conus medullaris between T12 & L2
42-45 cm long
occupies superior 2/3 of canal
anterior median fissure and posterior median fissure
B. Enlargements [N.149]
Cervical enlargement from C4 to T1- nerve supply to upper extremities
Lumbosacral enlargement from L2-S3- nerve supply to lower extremities
C. Internal Structure [N.151]
Central canal continuous with ventricles, fluid filled chambers of brain
Dorsal gray horn (axons of afferent sensory neurons) and ventral gray horn (cell body of efferent motor neurons) surround a central canal
Bundles of white matter (myelinated axons ascending/descending the spinal cord) surround the gray-matter horns.
D. Spinal Nerves [N.156]
31 pairs
Ventral nerve roots-efferent axons from ventral gray horn
Dorsal nerve roots- afferent axons to the dorsal gray horn
Run inferiorly within vertebral column
Ventral and dorsal nerve roots unite at intervertebral foramen to form mixed roots
Outside vertebral column, spinal nerves divide
Large ventral primary ramus-innervates ventral body regions
Smaller dorsal primary ramus-innervates dorsal body regions
Cauda equina
Bundle of lumbar and sacral nerve roots that occupy vertebral canal
Inferior to conus medullaris
V. Meninges [N.155]
Connective tissue membranes that surround and support spinal cord and cauda equina
Continuous with cranial meninges
A. Dura Mater
Outer most tubular sheath
Tough and fibrous
Anchored to periosteum at foramen magnum to S2 after spinal cord ends atL1-L2
Free within vertebral canal-not adherent to verbebral surfaces
Extends laterally into intervertebral foramina- form dural root sleeves with invest nerve roots and spinal ganglia
Epidural space-between dura mater and vertebral periosteum- contain fat and loose connective tissue
Subdural space-between dura matter and arachnoid matter- contain film of lubricating fluid
B. Arachnoid Mater
Intermediate membranous sheath
Delicate
Extends inferiorly to S2 and laterally to intervertebral foramen
Subarachnoid space-between arachnoid mater and pia mater- contains CSF and arachnoid trabeculae (delicate strands of connective tissue that loosely anchor arachnoid later to pial layer)
Lumbar cistern-Between L2 and S2- subarachnoid space reservoir of CSF
Contain cauda equina and filum terninale
C. Pia Mater
Innermost membranous covering
Adheres closely to suface of spinal cord and blood vessels
Gives rise to denticulate ligaments- suspends spinal cord within dural sheath
21 processes of connective tisse
Filum terminale is inferior termination of pia mater- attaches to coccyx
VI. Blood Supply
A. Arterial Supply [N.157]
3 longitudinal arteries supplemented by segmental radicular arteries
1. anterior spinal artery- supplies anterior 2/3 of cord
2. two posterior spinal arteries- supply posterior 1/3 of cord
radicular arteries- arise from larger vessels to enter the spinal canal via intervertebral foramen.
Spinal arteries and radicular arteries anastomose to form the arterial vasocorona (aterial plexus)
Great anterior radicular artery of Adamkiewicz provides major blood supply to inferior 2/3 of spinal cord.
B. Venous drainage [N.159]
Parallel arteries
Continuous with venous drainage of brain
Vertebral venous plexuses provide route for spread of infection and tumors from systemic regions to sp. cord and brain.
C. Spinal veins and sinuses
Anterior and posterior spinal veins
Usually 3 of each
Communicate feely and drain into numerous radicular viens
Internal vertebral venous plexus
Thin-walled and valveless
Occupies epidural space
External venous plexus
Communicates freely with internal vertebral venous plexus
Surrounds vertebral column
2. L
Tags: Annulus fibrosus, Anterior convexities, Arachnoid Mater, cauda equina, cervical, condyles, Costal facets, Dorsal gray horn, filum terninale, Interspinous ligament, Interspinous ligaments, Kyphosis, Ligamenta flava, Lordosis, nucleus pulposus, obesity, oseoporosis, pendulous abdomen, penous plexuses, Posterior convexitie, pregnancy, spinal nerves, Subarachnoid space, sway-back, thoracic vertebra, vertebrae, Vertebral Column Curvatures
