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Anatomy Tables - Deep Back & Spinal Cord |
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Osteology of the Vertebral Column |
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Bone | Structure | Description | Notes |
vertebra N 154,155,18, TG 1-05A, 1-05D |
one of a series of irregular bones that form the spine | a vertebra has two parts: the vertebral body and the vertebral arch; there are 33 vertebrae total: 7 cervical, 12 thoracic, 5 lumbar, 5 fused to form the sacrum, 4 coccygeal; features of a typical vertebra include: body, pedicles, transverse processes, laminae, articular processes, spinous process (Latin, vert = to turn) | |
vertebral body | the largest part of the vertebra | it is shaped like a short cylinder; adjacent vertebral bodies articulate through a symphysis | |
vertebral arch | the ring of bone formed by the paired pedicles and paired laminae of the vertebra | the transverse processes and spinous process are attached to the neural arch; the neural arch protects the spinal cord | |
pedicle | short strong process that extends posteriorly from the posterolateral surface of the vertebral body | paired; it connects the body with the transverse process; it is marked by superior & inferior vertebral notches; | |
transverse process | a lateral process that extends from the junction of the pedicle and the lamina of the vertebra | a site for muscle attachment and rib articulation | |
lamina | a broad flat plate of bone located between the transverse process and the spinous process of the vertebra | paired; it is flattened markedly in the anteroposterior direction; ligamenta flava span the interval between the laminae of adjacent vertebrae (Latin, lamina = thin plate) | |
articular processes | processes that project inferiorly and superiorly from the junction of the lamina and pedicle of the vertebra | two pairs on each vertebra (superior and inferior); the superior articular processes of one vertebra articulate with the inferior processes of the adjacent vertebra through synovial joints | |
intervertebral notch | a notch on the superior and inferior surface of the vertebral pedicle | the superior intervertebral notch of one vertebra combined with the inferior intervertebral notch of the adjacent vertebra forms the intervertebral foramen | |
intervertebral foramen | an opening between the pedicles of adjacent vertebrae | adjacent intervertebral notches form the intervertebral foramen; an opening for passage of the spinal nerve | |
vertebral canal | the opening formed by the combination of the body and the vertebral arch | it contains the spinal cord, meninges, epidural fat and the internal vertebral plexus of veins | |
spinous process | a posterior midline process arising from the junction of the two laminae of the vertebra | it projects downward and inferiorly; it is an important site of muscle attachment; spinous processes of cervical vertebra 2-6 are bifid | |
cervical vertebrae N 18 |
the seven vertebrae of the neck | cervical vertebrae have the features of the typical vertebra plus all have transverse foramina (for passage of the vertebral artery); C2-C6 have bifid spinous processes; cervical vertebrae have relatively small bodies; several cervical vertebra are named: atlas, axis, vertebra prominens | |
atlas (C1) N 17, TG 1-03A, 1-03B |
the first cervical vertebra | it has no vertebral body, only anterior & posterior arches; it articulates with the odontoid process of the axis (Greek, atlas refers to a titan who supported the earth on this shoulders as the atlas vertebra supports the head) | |
axis (C2) N 17, TG 1-03C |
the second cervical vertebra | the odontoid process (dens) projects superiorly from its body; it articulates with the anterior arch of the atlas (Latin, the axis provides the odontoid process which is the pivot about which the atlas vertebra rotates) | |
vertebra prominens | the seventh cervical vertebra (more properly, the vertebral spine of C7) | it has a long, non-bifid spinous process which is prominent at the nape of the neck, hence its name | |
thoracic vertebrae N 154 |
the 12 vertebrae associated with the thoracic region | thoracic vertebrae have the features of a typical vertebra plus they are characterized by long slender spines that project inferiorly; they have facets for articulation with ribs; thoracic vertebrae have bodies of intermediate size | |
costal articular facet on the body | small smooth areas at the junction of the body and the vertebral arch | most thoracic vertebrae have 2 costal facets on each side (one superior and one inferior); the superior costal facet of one vertebra and the inferior costal facet of the adjacent vertebra both articulate with the head of the same rib; also known as demifacets | |
costal articular facet on the transverse process | a small smooth area on the transverse process of the thoracic vertebra | it articulates with the articular facet on the tubercle of the rib | |
lumbar vertebrae N 155 |
the 5 vertebrae located in the lumbar region | lumbar vertebrae have the features of a typical vertebra plus they are characterized by short, blunt spines that project posteriorly; lumbar spines do not overlap making the lumbar level a good one for spinal tap; lumbar vertebrae are built strong and have the largest bodies of all vertebrae | |
sacrum N 157, TG 1-08A, 1-08B |
a triangular bone that is the posterior skeletal element forming the pelvis | it is formed by 5 fused vertebrae; the sacrum and two os coxae bones form the pelvis. (Latin, os sacrum = Holy Bone. "Holey" bone could remind you of the sacral foramina.) | |
anterior sacral foramina | an opening in the anterior surface of the sacrum | there are four pairs; each transmits the ventral primary ramus of the respective sacral spinal nerve; branches of the lateral sacral aa. enter the sacral canal through these openings (Latin, foramen = an aperture) | |
posterior sacral foramina | an opening in the posterior surface of the sacrum | there are four pairs; each transmits the dorsal primary ramus of the respective sacral spinal nerve (Latin, foramen = an aperture) | |
sacral canal | the opening in the center of the sacrum | it is the continuation of the vertebral canal at sacral vertebral levels | |
sacral hiatus TG 1-08B |
an opening in the posterior surface of the sacrum in the midline | it is a normal feature that results from the failure of fusion of the laminae of the fifth sacral segment (and sometimes the fourth) during development (Latin, hiatus = to yawn) | |
coccyx N 157, TG 1-08B |
the most inferior portion of the vertebral column | the coccyx results from the fusion of the four coccygeal vertebrae; it may be a single bone or the first coccygeal vertebra may be separated from the other three; it articulates with the fifth sacral segment; coccygeal vertebrae are reduced in complexity, having no pedicles, laminae or spines. (Latin/Greek, coccyx = cuckoo's beak) |
Muscles of the Back Region - Intermediate Group |
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Muscle | Origin | Insertion | Action | Innervation | Artery | Notes | Image |
serratus posterior inferior N 175 |
thoracolumbar fascia, spines of vertebrae T11-T12 and L1-L2 | ribs 9-12, lateral to the angles | pulls down lower ribs | branches of the ventral primary rami of spinal nerves T9-T12 | lowest posterior intercostal a., subcostal a., first two lumbar aa. | a respiratory muscle, it receives ventral ramus innervation; embryonically related to the intercostal muscles, not the deep back mm. (Latin, serratus = to saw) | |
serratus posterior superior N 175 |
ligamentum nuchae, spines of vertebrae C7 and T1-T3 | ribs 1-4, lateral to the angles | elevates the upper ribs | branches of the ventral primary rami of spinal nerves T1-T4 | posterior intercostal aa. 1-4 | a respiratory muscle, it receives ventral ramus innervation; embryonically related to the intercostal muscles, not the deep back mm. (Latin, serratus = to saw) |
Muscles of the Back Region - Deep Group |
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Muscle | Origin | Insertion | Action | Innervation | Artery | Notes | Image |
erector spinae N 175, 176, TG 1-14 |
iliac crest, sacrum, transverse and spinous processes of vertebrae and supraspinal ligament | angles of the ribs, transverse and spinous processes of vertebrae, posterior aspect of the skull | extends and laterally bends the trunk, neck and head | segmentally innervated by dorsal primary rami of spinal nerves C1-S5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the erector spinae m. is separated into 3 columns of muscle: iliocostalis laterally, longissimus in an intermediate position and spinalis medially; each of these columns has multiple named parts |
Joints and Ligaments of the Vertebral Column |
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Joint or ligament | Description | Notes |
interspinous ligament N 158,159, TG 1-10A, 1-11A | a ligament that connects the spinous processes of two adjacent vertebra | a syndesmosis |
intervertebral disc N 158,159, TG 1-10A,1-11A |
a fibrocartilaginous disc between adjacent vertebral bodies | a symphysis; it is composed of two parts: an outer anulus fibrosus and an inner nucleus pulposus; the nucleus pulposus is the remnant of the notochord; the intervertebral discs are important shock absorbers between vertebrae |
ligamenta flava N 158, 1-11A, 1-11B |
a ligament formed predominantly by elastic fibers which joins the laminae of adjacent vertebrae | a syndesmosis; paired; the ligamentum flavum is penetrated by the needle during spinal tap (Latin, flavus = yellow, a reference to the predominance of yellow elastic fibers which gives this ligament its grossly visible color) |
nuchal ligament |
a midline ligament that extends posteriorly from the spinous processes of cervical vertebrae and extends from the base of the skull to the 7th cervical vertebra | a syndesmosis; it provides muscle attachments to the cervical spinous processes without the necessity of long spinous processes that would hinder extension of the neck; a.k.a. ligamentum nuchae (Latin, nucha = nape) |
anterior longitudinal ligament N 158,159, TG 1-10A,1-11A |
a ligament that courses from superior to inferior along the anterior surfaces of all vertebral bodies | it lies directly posterior to the thoracic and abdominal viscera |
posterior longitudinal ligament N 158, TG 1-10A,1-11A |
a ligament that courses from superior to inferior along the posterior surfaces of all vertebral bodies | it is broader at the intervertebral discs and narrow at the vertebral bodies which gives it a scalloped edge; it is located in the vertebral canal; it is NOT penetrated by the needle during spinal tap |
supraspinous ligament N 158,159, TG 1-10A, 1-10B, 1-11A, 1-11B |
a ligament that connects the tips of the spinous processes of thoracic and lumbar vertebrae | a syndesmosis; the supraspinous ligament begins at the C7 vertebra and ends at the mid-sacral segmental level; it serves as a muscle attachment site |
zygapophyseal joint N 158, 1-11A, 1-11B |
a small joint between the articular processes of adjacent vertebrae | a synovial plane joint |
Arteries of the Spinal Cord & Vertebral Column |
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Artery | Source | Branches | Supply to | Notes |
radicular, anterior N 172, TG 1-19, 1-21 |
they arise as multiple branches of several vessels (vertebral, posterior intercostal, lumbar, and lateral sacral aa.) | they accompany the ventral rootlets to reach the spinal cord | meninges; spinal cord; spinal nerve; ventral rootlets | anterior radicular aa. anastomose with the anterior spinal a. |
radicular, great anterior N 172, TG 1-19, 1-21 |
the spinal br. of the lower posterior intercostal a., subcostal a., or upper lumbar a., usually on left | no named branches | lower spinal cord | great anterior radicular a. anastomoses with the anterior spinal a. at lower thoracic or upper lumbar spinal cord levels |
radicular, posterior N 172, TG 1-19, 1-21 |
they arise as multiple branches of several vessels (vertebral, posterior intercostal, lumbar, and lateral sacral aa.) | no named branches | meninges; spinal cord; spinal nerve; dorsal rootlets | posterior radicular aa. accompany the dorsal rootlets; they anastomose with the posterior spinal aa. |
spinal, anterior N 171,172, TG 1-19, 1-21 |
contributions received from several arteries (vertebral, posterior intercostal, subcostal, lumbar, lateral sacral aa.) | pial arterial plexus | meninges; spinal cord; medulla (dorsal motor nucleus of cranial nerve X, nucleus ambiguus, spinal accessory nucleus and hypoglossal nucleus) | the anterior spinal a. anastomoses with the anterior radicular brs. of the spinal rami of the vertebral, posterior intercostal, subcostal, lumbar and lateral sacral aa. |
spinal, posterior N 171,172, TG 1-19, 1-21 |
contributions received from several arteries (posterior inferior cerebellar, vertebral, posterior intercostal, subcostal, lumbar, lateral sacral aa.) | pial arterial plexus | spinal cord, especially the dorsal columns; medulla (nucleus cuneatus and nucleus gracilis) | paired; posterior spinal aa. anastomose with the posterior radicular brs. of the spinal rami of the vertebral, posterior intercostal, subcostal, lumbar and lateral sacral aa. |
Veins of the Spinal Cord & Vertebral Column |
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Vein | Tributaries | Drains Into | Region Drained | Notes |
vertebral plexus, external N 170,173, TG 1-22A, 1-22B |
adjacent segmental vs. | vertebral column & associated muscles | connects with internal vertebral plexus | |
vertebral plexus, internal N 170,173, TG 1-22A, 1-22B |
adjacent segmental vs. | spinal cord, meninges, vertebral column | connects with external vertebral plexus |
Nervous Structures |
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Nerve | Source | Branches | Motor | Sensory | Notes |
dorsal primary ramus N 169,257, TG 1-17 |
first branch off of the dorsal side of the spinal nerve | numerous | to the deep back mm.; sympathetic innervation to the skin | general sense (touch, pressure, pain, heat, cold, etc.) to the skin of the back | a mixed nerve containing both motor and sensory fibers (Latin, ramus = branch) |
dorsal root N 169,257, TG 8-05 |
multiple rootlets from the dorsal horn of the spinal cord to the spinal nerve | none | none | general sense (touch, pressure, pain, heat, cold, etc.) | dorsal root is entirely sensory in function; it is located dorsal to the denticulate ligament |
dorsal root ganglion N 169,257, TG 1-17, 1-19 |
dorsal rootlets | dorsal root | none | one dermatome | a sensory ganglion located along the dorsal root within the intervertebral foramen - one per spinal nerve; location of the cell bodies of somatic afferent (sensory) neurons |
spinal n. N 169,257, TG 1-17 |
formed at the point where the dorsal and ventral rootlets meet; it ends where the dorsal and ventral primary rami diverge | dorsal primary ramus; ventral primary ramus | to skeletal mm.; some levels carry preganglionic sympathetic axons (T1-L2) | general sense (touch, pressure, pain, heat, cold, etc.) from the entire surface of the neck, trunk and extremities; visceral pain (via the white ramus communicans and the sympathetic nervous system) | located at the intervertebral foramen; there are 31 pairs of spinal nerves - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal |
ventral primary ramus N 169,257, TG 1-17 |
first branch off of the ventral side of the spinal nerve | numerous | to skeletal mm. of the neck, trunk and extremities; sympathetic innervation to the skin | general sense (touch, pressure, pain, heat, cold, etc.) to the skin of the trunk (except the back) and extremities; visceral pain via the white rami of the sympathetic nervous system (T1-L2) | a mixed nerve containing both motor and sensory fibers (Latin, ramus = branch) |
ventral root N 169,257, TG 1-17, 1-19 |
multiple rootlets from the ventral horn of the spinal cord to the spinal nerve | none | to skeletal mm.; preganglionic sympathetic (T1-L2) | none | entirely motor in function; located ventral to the denticulate ligament; at all spinal core levels it contains GSE for skeletal mm.; at levels T1-L2 it contains GVE (preganglionic sympathetic) for blood vessels, sweat glands, thoracic viscera, abdominal viscera, pelvic viscera |
Spinal Meninges & Spinal Cord |
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Structure | Location/Description | Notes |
spinal cord N 165, N 169 |
lies within the dural sac in vertebral canal; continuous with medulla oblongata at foramen magnum of skull; ends inferiorly at L1/2 intervertebral disc | spinal cord and brain are the central nervous system; their branches comprise the periperal nervous system |
gray matter N 165, TG 1-21 |
butterfly-shaped core of the spinal cord, containing neuron cell bodies | ventral horns of gray mater contain motor neurons, dorsal horns contain sensory neurons, lateral horns contain autonomic nerve cell bodies |
white matter N 165, TG 1-21 |
surrounds the gray matter of spinal cord, contains nerve processes ascending and descending the cord | white color derives from fatty myelin covering of nerve processes |
anterior median fissure | a longitudinal midline fissure located on the ventral surface of the spinal cord | the anterior spinal artery lies in this fissure ventrally |
posterior median sulcus | a longitudinal midline groove located on the dorsal surface of the spinal cord | |
cervical enlargement N 161, TG 1-18 |
vertebral level C4 through T1 | created by the rootlets of spinal nerves C5-T1 that form the brachial plexus |
lumbosacral enlargement N 161, TG 1-18 |
vertebral level T11 through L1 | created by the rootlets of spinal nerves L1-S4 that form the lumbosacral plexus |
conus medullaris N 160,161, TG 1-20 |
cone-shaped inferior end of the spinal cord; located at vertebral level L1 | at birth, the conus medullaris is at the level of L2/L3 (Latin/Greek, conus = cone) |
cauda equina N 160,161, TG 1-20 |
dorsal and ventral roots of all spinal nerves inferior to L1 | lies within the lumbar cistern (Latin, cauda equina = horse's tail) |
arachnoid mater N 169, TG 1-19 |
intermediate one of the three layers of meninges | arachnoid mater is a thin membrane which is pressed against the inner surface of the dura mater by cerebrospinal fluid pressure; (Greek, arachnoids = spider ), the space deep to this layer (subarachnoid space) has a spider web-like appearance |
denticulate ligament TG 1-19 |
a lateral extension of pia mater from the spinal cord | denticulate ligament attaches to the dura mater to anchor the spinal cord; it forms a scalloped free border; there are 2 (one on each side) |
dura mater N 169, TG 1-18, 1-19 |
outermost of the meningeal layers covering the brain and spinal cord | Latin for "tough mother"; it is the most durable of the meninges and provides support and protection for the brain and spinal cord; two types are described which differ in structure: cranial and spinal |
dura mater, spinal N 169, TG 1-18, 1-19 |
outermost covering of the spinal cord, it forms the dural sac containing the spinal cord within vertebral canal | dural sac ends at S2, coccygeal ligament (filum terminale externum) continues inferiorly to attach to coccyx (Latin, dura mater = tough mother) |
epidural fat N 170,173, TG 1-22A, 1-22B |
loose connective tissue within the epidural space | upon the dura mater |
epidural space N 170,173, TG 1-22A, 1-22B |
the space external to the sac of spinal dura mater within the vertebral canal | the epidural space contains epidural fat and the internal vertebral plexus of veins which is valveless (clinically relevant as potential route for hematogenous metatasis) |
filum terminale internum N 160,161, TG 1-20 |
thread-like extension of the pia mater from the conus medullaris of the spinal cord | filum terminale internum is best seen between vertebral levels L2 and S2; it becomes enclosed within the filum terminale externum (Latin, filum = thread) |
filum terminale externum N 159,160,161, TG 1-18, 1-20 |
thread-like extension of the dura mater below the end of the dural sac at S2 | it attaches to the coccyx; also known as the coccygeal ligament (Latin, filum = thread) |
meninges | three layers of connective tissue covering the brain and spinal cord; dura mater, arachnoid mater, and pia mater | meninges provide protection and nourishment of the brain, brainstem and spinal cord (Greek, menin- = membrane) |
pia mater N 169, TG 1-19 |
delicate membrane that lies on surface of the brain and spinal cord | Latin, pia mater = delicate mother; it is the most delicate of the meninges; this layer faithfully follows all surface contours of the brain and spinal cord; pia mater has 2 specializations: denticulate ligament and filum terminale internum |
subdural space N 169 |
the space between the dura mater and the arachnoid mater | this is a potential space only; the pressure of CSF in the subarachnoid space pushes arachnoid against dura |
subarachnoid space N 169, TG 1-19 |
the space between the arachnoid and the pia mater | subarachnoid space contains cerebrospinal fluid and spider web-like filaments (Greek, arachnoids = spider ) |
The material presented in these tables is contained in the book: MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger Published by ILOC, Inc., New York Copyright © 1995, unauthorized use prohibited. |
The excellent editorial assistance of Dr. Pat Tank, UAMS is gratefully acknowledged. |