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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) |
Viscera/Fascia |
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|---|---|
| Organ/Part of Organ | Location/Description |
| skin | the membranous covering of the body, also known as the cutis |
| epidermis | the outer epithelial portion of the skin including these layers (from superficial to deep): stratum corneum (or horny layer), stratum lucidum (or clear layer), stratum granulosum (or granular layer), stratum spinosum (or spiney layer), stratum germintivum (or germinative layer), stratum basale (or basal layer) (Greek, epi = on + derma = skin) |
| dermis | blood, lymph vessels, nerves, sebaceous glands, and sweat glands occur in this layer of the skin, which lies between the epidermis and fatty (subcutaneous) layer |
| superficial fascia | also known as the subcutaneous tissue, this layer lies deep to the skin and consists of loose connective tissue containing fat, cutaneous nerves, superficial veins, lymph vessles and nodes (Latin, sub = beneath + cutis = skin) |
| investing (deep) fascia | a dense layer of connective tissue between the subcutaneous tissue and the muscles; surrounds the entire muscle group |
| muscular fascia | a dense layer of connective tissue surrounding individual muscles |
| neurovascular bundle | a term that describes the typical common path of a vein, artery, and nerve |
| thoracolumbar aponeurosis (fascia) (N4, TG1-13) | extends laterally from the spinous processes and forms a thin covering for the deep muscles in the thoracic region and a strong, thick covering for muscles in the lumbar region. |
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 | |
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 anterior N 167 | ribs 1-8 or 9 | medial border of the scapula on its costal (deep) surface | it draws the scapula forward; the inferior fibers rotate the scapula superiorly | long thoracic nerve (from ventral rami C5-C7) | lateral thoracic a | a lesion of long thoracic nerve will cause winging of the scapula (i.e., the medial border of the scapula falls away from the posterior chest wall and looks like an angel's wing) (Latin, serratus = to saw) | ) |
| 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 168, 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 | ) |
| iliocostalis N 168, TG 1-14 |
iliac crest and sacrum | angles of the ribs | extends and laterally bends the trunk and neck | dorsal primary rami of spinal nerves C4-S5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the most lateral part of the erector spinae; it may be subdivided into lumborum, thoracis and cervicis portions | ) |
| interspinales N 169, TG 1-15 | upper border of spinous process | lower border of spinous process above | extend trunk and neck | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | these are small and fairly insignificant muscles | ) |
| intertransversarii N 169, TG 1-15 | upper border of transverse process | lower border of transverse process above | laterally bend trunk and neck | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | these are small and fairly insignificant muscles | ) |
| longissimus N 168, TG 1-14 | transverse process at inferior vertebral levels | transverse process at superior vertebral levels and mastoid process | extends and laterally bends the trunk, neck and head | dorsal primary rami of spinal nerves C1-S1 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the intermediate part of the erector spinae;it may be subdivided into thoracis, cervicis and capitis portions | ) |
| multifidus N 169, TG 1-15 | sacrum, transverse processes of C3-L5 | spinous processes 2-4 vertebral levels superior to their origin | extend and laterally bend trunk and neck, rotate to opposite side | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | semispinalis, multifidus and rotatores make up the transversospinal muscle group | ) |
| rotatores N 169, TG 1-15 | transverse processes | long rotatores: spines 2 vertebrae above origin; short rotatores: spines 1 vertebrae above origin | rotates the vertebral column to the opposite side | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | semispinalis, multifidus and rotatores make up the transversospinal muscle group | ) |
| semispinalis N 168, 169, TG 1-14, 1-15 |
transverse processes of C7-T12 | capitis: back of skull between nuchal lines; cervicis & thoracis: spines 4-6 vertebrae above origin | extends the trunk and laterally bends the trunk, rotates the trunk to the opposite side | dorsal primary rami of spinal nerves C1-T12 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | three parts are named based on their insertions: capitis, cervicis and thoracis; semispinalis, multifidus and rotatores make up the transversospinal muscle group | ) |
| spinalis N 168, 169, TG 1-14 |
spinous processes at inferior vertebral levels | spinous processes at superior vertebral levels and base of the skull | extends and laterally bends trunk and neck | dorsal primary rami of spinal nerves C2-L3 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | most medial part of the erector spinae; may be subdivided into thoracis, cervicis and capitis portions | ) |
| splenius N 167, 168, TG 1-14 |
ligamentum nuchae and spines C7-T6 | capitis: mastoid process & superior nuchal line laterally; cervicis: posterior tubercles of C1-C3 vertebrae | extends and laterally bends neck and head; rotates head to same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | splenius means bandage; it gets its name from its broad, flat shape | ) |
| splenius capitis N 167, 168, TG 1-14 |
ligamentum nuchae and spines of C7-T6 vertebrae | mastoid process and lateral end of the superior nuchal line | extends and laterally bends the neck and head, rotates head to the same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | named for its shape: splenius means bandage and capitis refers to the insertion of this portion of the muscle | |
| splenius cervicis N 167, 168, TG 1-14 | ligamentum nuchae and spines of C7-T6 vertebrae | posterior tubercles of the transverse processes of C1-C3 vertebrae | extends and laterally bends neck and head, rotates head to the same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | named for its shape: splenius means bandage and cervicis refers to the insertion of this portion of the muscle | ) |
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) |
Blood Vessels of the Back and Neck |
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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 |
| occipital (N171, TG1-16, G4.38, G4.39) | external carotid a. | sternocleidomastoid brs., auricular br., mastoid br., descending br., occipital brs. | lateral neck, posterior neck, posterior scalp | occipital a. anastomoses with the deep cervical a.; it courses with the greater occipital nerve on the posterior surface of the head |
| 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 |
Nerves of the Back |
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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 (N171, 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 |
| occipital, lesser (N171, TG1-16, G4.38, G4.39) |
ventral primary ramus of spinal nerve C2 | no named branches | none | skin behind the ear | 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 | |||
Clinical Terms |
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|---|---|
| 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. |
| 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. |
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