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Anatomy Tables - Back & Spinal Cord
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Anatomy Tables - Back & Spinal Cord |
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Bones of the Back Region |
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|---|---|---|---|
| Bone | Structure | Description | Notes |
| occipital (N4, TG7-05) |
the bone forming the posterior surface of the skull | it articulates superolaterally with the parietal bones through the lambdoid suture, anteroinferiorly with the temporal bone and anteriorly with the body of the sphenoid bone (Latin, occiput = against head) | |
| external occipital protuberance (N4, TG7-05) |
a low process on the external surface of the occipital bone in the midline | it is an attachment site for the ligamentum nuchae; the superior nuchal lines of the two sides meet in the midline at the external occipital protuberance; also known as: inion (Latin, occiput = against head; Greek, inion = back of head) | |
| mastoid process (N4,N8,N13, TG7-05, TG7-06) |
the process located posteroinferior to the external acoustic meatus | it projects inferiorly from the junction of the petrous and squamous parts of the temporal bone; it contains the mastoid air cells that open into tympanic cavity through the mastoid antrum (Latin/Greek, mastoides = resembling a nipple) | |
| superior nuchal line (N174, TG7-06) |
a low ridge that runs transversely on the external surface of the squamous part of the occipital bone | it is an attachment site for trapezius and splenius mm. (Latin, nucha = nape) | |
| vertebra | 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 | |
| spinous process (N21, TG1-03D, TG1-03E, TG1-05B, TG1-05E) |
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 | |
| vertebra prominens (N21, TG1-01) |
the seventh cervical vertebra | it has a long, non-bifid spinous process which is prominent at the nape of the neck, hence its name | |
| sacrum (N157, TG1-08) |
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" meant "Holy Bone". "Holey" bone could remind you of the sacral foramina.) | |
| 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) | |
| coccyx (N157, TG6-04) |
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) | |
| pectoral girdle (N420, N421, TG2-03A) |
formed by the scapulae and clavicles and joined to the manubrium, it connects the upper limbs to the axial skeleton | ||
| clavicle (TG2-03A) |
an "S" shaped bone located between the sternum and the scapula | it articulates medially with the manubrium of the sternum and laterally with the acromion process of the scapula; it forms a strut that supports the upper limb; it is frequently fractured; it is the first bone to begin ossification during development (Latin, clavicula = little key, this term was used to refer to the catch that fastens a window as well as to keys. Curved window fasteners resemble the shape of this bone) | |
| scapula (TG2-03A, TG2-03B) |
the bone of the shoulder | the scapula floats in a sea of muscles, so it is difficult to fracture; it articulates with the axial skeleton through only one bone - the clavicle at the coracoclavicular and acromioclavicular joints | |
| medial border | the border of the scapula that runs from the superior angle to the inferior angle | it is an important site of muscle attachments for the intermediate layer of back muscles, including rhomboid major and minor and serratus anterior | |
| superior angle | the angle of the scapula formed at the union of the superior and medial borders | it is the attachment site for the levator scapulae m. | |
| inferior angle | the angle of the scapula formed by the union of the medial and lateral borders | the inferior angle of the scapula often has a slip of origin of the latissimus dorsi attached to it | |
| spine | a heavy ridge that runs from the medial border of the scapula to the acromion process | it supports the acromion process; it divides the posterior surface of the scapula into a supraspinatous fossa and an infraspinatous fossa | |
| acromion | a broad, flat process located at the lateral end of the scapular spine | it articulates with the clavicle through a synovial joint (acromioclavicular joint) (Greek, akros = point) | |
| ilium (N152,N174, N248, TG6-04) |
fan-shaped bone that forms the lateral prominence of the pelvis | one of three bones that form the os coxae: ilium, ischium, pubis | |
| iliac crest | arching superior edge of the ilium that forms the rim of the "fan" | attachment for abdominal wall muscles | |
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) | |
Topographical Anatomy of the Back |
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|---|---|---|
| Structure/Space | Description/Boundaries | Significance |
| external occipital protuberance (N4, TG7-05) |
a projection on the external surface of the squamous part of the occipital bone in the midline | it is the attachment site of the ligamentum nuchae and the trapezius m.; its highest point is called the inion (Latin, occiput = against head; Greek, inion = back of head) |
| vertebra (spina) prominens (N21, TG1-01) |
the seventh cervical vertebra | it has a long, non-bifid spinous process which is prominent at the nape of the neck, hence its name (Latin, vert = to turn) |
Joints and Ligaments |
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|---|---|---|
| Joint or ligament | Description | Notes |
| nuchal ligament (N21, TG1-09) |
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 (Latin, nucha = nape) |
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 |
Muscles of the Back Region - Superficial Group |
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|---|---|---|---|---|---|---|---|
| Muscle | Origin | Insertion | Action | Innervation | Artery | Notes | Image |
| latissimus dorsi (N174, TG1-13) |
vertebral spines from T7 to the sacrum, posterior third of the iliac crest, lower 3 or 4 ribs, sometimes from the inferior angle of the scapula | floor of the intertubercular groove | extends and rotates the arm medially, along with adduction of the arm | thoracodorsal nerve (C7,8) from the posterior cord of the brachial plexus | thoracodorsal a. | the inserting tendon twists so that fibers originating highest insert lowest (Latin, latus = broad, dorsi = back) | ) |
| levator scapulae (N424, TG1-13) |
transverse processes of C1-C4 vertebrae | medial border of the scapula from the superior angle to the spine | elevates the scapula | dorsal scapular nerve (C5); the upper part of the muscle receives branches of C3 & C4 | dorsal scapular a. | levator scapulae is named for its action (Latin, levator = to lift) | ) |
| rhomboideus major (N424, TG1-13) |
spines of vertebrae T2-T5 | medial border of the scapula inferior to the spine of the scapula | retracts, elevates and rotates the scapula inferiorly | dorsal scapular nerve (C5) | dorsal scapular a. | named for its shape (Greek, rhomb = oblique parallelogram) | ) |
| rhomboideus minor (N424, TG1-13) |
inferior end of the ligamentum nuchae, spines of vertebrae C7 and T1 | medial border of the scapula at the root of the spine of the scapula | retracts, elevates and rotates the scapula inferiorly | dorsal scapular nerve (C5) | dorsal scapular a | named for its shape (Greek, rhomb = oblique parallelogram | ) |
| trapezius (N174, TG1-13) |
medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of vertebrae C7-T12 | lateral third of the clavicle, medial side of the acromion and the upper crest of the scapular spine, tubercle of the scapular spine | elevates and depresses the scapula (depending on which part of the muscle contracts); rotates the scapula superiorly; retracts scapula | motor: spinal accessory (XI), proprioception: C3-C4 | transverse cervical a. | named for its shape; trapezius is an example of a muscle that migrates during development from its level of origin (cervical) to its final position, pulling its nerve and artery along behind | ) |
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 | ) |
Arteries of the Back - Superficial |
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|---|---|---|---|---|
| Artery | Source | Branches | Supply to | Notes |
| dorsal scapular (N33,N427, N429,N430,N477, TG2-09) |
subclavian a., 3rd part | unnamed muscular branches | levator scapulae m., rhomboideus major m., rhomboideus minor m. | dorsal scapular a. anastomoses with the suprascapular a. and the subscapular a. to form the scapular anastomosis; dorsal scapular a is a branch of the transverse cervical a. in ~30% of cases |
| thoracodorsal (N429, TG1-13) |
subscapular | muscular | latissimus dorsi | |
| transverse cervical (N33,N177,N427, TG1-13) |
thyrocervical trunk | unnamed muscular branches, possibly the dorsal scapular a. | trapezius muscle and surrounding tissues | transverse cervical a. gives rise to the dorsal scapular a. ~30% of the time |
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 | |
Nerves of the Back - Superficial |
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|---|---|---|---|---|---|
| Nerve | Source | Branches | Motor | Sensory | Notes |
| accessory n. (N177, TG7-93C) |
cranial root: medulla - nucleus ambiguus; spinal root: spinal nucleus of the upper cervical spinal cord | no named branches | GSE: sternocleidomastoid and trapezius mm. | none | also known as: CN XI, 11th cranial nerve; spinal root enters cranial cavity by passing through the foramen magnum; exits skull by passing through the jugular foramen; accessory n. is motor only; the subtrapezial plexus of nerves receives proprioceptive fibers: for the sternocleidomastoid m. from the ventral primary rami of spinal nn. C2 and C3 - for trapezius via ventral primary rami of C3 and C4 |
| dorsal primary ramus (N258, TG1-12) |
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 scapular n. (N33,N427,N429, N430,N477, TG2-09) |
brachial plexus (br. of C5 ventral primary ramus) | no named branches | rhomboideus major and minor mm.; levator scapulae m. | none | dorsal scapular n. passes through the scalenus medius m. |
| occipital n., greater (N178, TG1-16) |
dorsal primary ramus of spinal nerve C2 (medial br.) | no named branches | posterior neck muscles | skin of the posterior surface of the scalp | muscles innervated by this nerve develop from epimeres in the embryo |
| spinal n. (N258, TG1-12) |
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 |
| thoracodorsal (middle subscapular) (N429, TG1-13) |
posterior cord of brachial plexus | latissimus dorsi | |||
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 ) |
Clinical Terms |
|
|---|---|
| Term | Definition |
| triangle of auscultation (N424, TG1-13) |
a triangular gap formed by the superior horizontal border of the latissimus dorsi, the medial border of the scapula, and the inferolateral border of the trapezius; this is a good place to examine posterior segments of the lungs with a stethoscope |
| lumbar triangle (Petit's triangle)/hernia (N174, TG1-13) |
bordered medially by the latissimus dorsi, laterally by the external abdominal oblique, and inferiorly by the iliac crest, this point is vulnerable to abdominal (lumbar) hernia. The definition of a hernia is the protrusion of a portion of an organ or tissue through an abnormal opening. |
| slipped/herniated disc | herniation of the nucleus pulposis through a weakened anulus fibrosus, usually posterolaterally; it 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 disk;" these occur most frequently in the cervical and lumbar regions due to these segments being the most mobile. Cervical disk disease usually presents in patients older than the age of 50, and patients complain of pain (radiating down the arm), paresthesia and dysasthesia (abnormal sensations), and weakness. Lumbar disease presents with similar symptoms in the lower extremities. Both conditions are diagnosed via MRI. |
| radiculopathy | compression or lesion of spinal nerve roots |
| pinched nerve | refers to spinal nerves compressed by herniated discs or spondylosis; pain and sensory loss follows the dermatome; motor loss may also occur |
| laminectomy | removal of one or more laminae of the vertebrae; this is often done to remove a herniated disc (Latin, lamina = thin plate) |
| nerve root avulsion | tearing away of the nerve roots from the spinal cord. This does not often occur in the cervical spine as the transverse processes of vertebrae here have chutes or grooves in which the spinal nerves lie. Connective tissue attaches the nerve fibers to the chutes and any trauma will sever the nerves distal to the chutes instead of tearing them from the spinal cord. Distal injuries are easier to repair. |
| lumbar puncture (aka spinal tap) | this procedure is used to gather CSF fluid, which is an excellent diagnostic tool; CNS infections, blood and other pathologies can affect content of this vital fluid; to perform a lumbar puncture, the patient is lying on the side with the back flexed (spreads everything out). A needle is inserted between the spinous processes of L3 and L4 or L4 and L5. A superficial landmark for finding this point is the supracristal line which runs on a line from the iliac crests and passes through L4's spinous process |
| meningitis | infection of the meninges (either bacterial or viral). Patients typically present with the triad of fever, headache, and signs of meningeal irritation (such as neck stiffness). (Greek, menin- = membrane, -itis = inflammation) |
| epidural anesthesia | injection of anesthetic agents into the epidural space as opposed to injection into the subarachnoid space; usually takes 10 to 20 minutes to take effect and has a direct effect on the spinal nerves; this procedure is often used in childbirth and cesarean sections |
| spinal anesthesia | an anesthetic agent is injected directly into the subarachnoid space at the L3/L4 vertebral level, anesthetizes essentially everything inferior to the waist; the anesthesia takes effect in about a minute; this procedure can result in the patient experiencing a headache due to fluid leaking from the puncture site. Patients must be carefully monitored as sometimes (about 1 out of every 100) the anesthetic agent can travel upward and block autonomic nerves slowing the heart and depressing respirations. |
| caudal anesthesia | this procedure is done using an in-dwelling catheter in the sacral canal; the catheter is inserted through the sacral hiatus, and the anesthetic bathes the sacral nerve roots; the position of the patient and the amount of fluid injected determines the height to which the anesthetic ascends |
| spina bifida | a defect in the spinal column due to failure of development or fusion of the vertebral arches with varying levels of severity depending on the involvement of the spinal cord and meninges. The incidence of this has been dramatically reduced with the discovery that proper maternal intake of folic acid can prevent this in most cases. |
| hydrocephalus | a condition that causes dilation of the cerebral ventricles due to excessive accumulation of cerebrospinal fluid. This may lead to separation of the cranial bones and enlargement of the head.(Greek, hydro = water) |
| myelomeningocele | a congenital defect that results in the failure of the closure of the neural arches, resulting in herniation of the spinal cord and its meninges through the defect in the vertebral column. (Greek, myelos = spinal cord + menin- = membrane + cele = hernia) |
| 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. |