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Anatomy Tables - Superficial Back
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Anatomy Tables - Superficial Back |
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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) |
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 | ) |
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 |
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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 |
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 (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 | |||
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. |