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Trunk, Front & Back Musculature
Muscle Regions of the Body:
Muscle Groups within this Region:
Superficial Back Musculature
Trapezius
 | Origin:
- external occipital protuberance
- along the medial sides of the superior nuchal line
- ligamentum nuchae (surrounding the cervical spinous processes)
- spinous processes of C1-T12
|
| Insertion:
- posterior, lateral 1/3 of clavicle
- acromion
- superior spine of scapula
|
| Action:
- elevates scapula
- upward rotation of the scapula (upper fibers)
- downward rotation of the scapula (lower fibers)
- retracts scapula
|
| Blood: transverse cervical artery |
| Nerve:
- spinal Accessory (XI) (efferent or motor fibers)
- ventral ramii of C3 & C4 (afferent or sensory fibers)
|
Latissimus dorsi
| Origin:
- spinous process of T7-L5
- upper 2-3 sacral segments
- iliac crest
- lower 3 or 4 Ribs
|
| Insertion: lateral lip of the intertubercular groove |
| Action:
- adduction of humerus
- medial rotation of the humerus
- extension from flexed position
- downward rotation of the scapula
|
| Blood: thoracodorsal artery |
| Nerve: thoracodorsal nerve, C6,7,8 |
Pectoral Musculature
Subclavius
| Origin: first rib about the junction of bone and cartilage |
| Insertion: lower surface of clavicle |
| Action: assists in stabilizing the clavicle |
| Blood: clavicular branch of thoracoacromial artery |
| Nerve: nerve to the subclavius, C5,6 |
Pectoralis major
| Origin:
- medial 1/3 of clavicle
- anterior aspect of manubrium & length of body of sternum
- cartilaginous attachments of upper 6 ribs
- external oblique's aponeurosis
|
| Insertion:
- lateral lip of bicipital groove to the crest of the greater tubercle
- clavicular fibers insert more distally; sternal fibers more proximally
|
| Action:
- adducts humerus
- medially rotates humerus
- flexion of the arm from extension (clavicular portion)
|
| Blood:
- pectoralis branch of thoracoacromial artery (runs with lateral pec. nerve)
- lateral thoracic artery (lesser supply, and runs with medial pectoral nerve)
|
| Nerve:
- lateral pectoral nerve, C5,6,7 to clavicular portion
- medial pectoral nerve, C8,T1 to sternal portion
|
Pectoralis minor
| Origin: outer surface of ribs 2-5 or 3-5 or 6 |
| Insertion: medial aspect of coracoid process of the scapula |
| Action:
- depresses & downwardly rotates the scapula
- assists in scapular protraction from a retracted position
- stabilizes the scapula
|
| Blood: lateral thoracic artery |
| Nerve: medial pectoral nerve, C8,T1 |
Shoulder Girdle Musculature
Levator scapulae
| Origin: transverse processes of C1-C3 or C4 |
| Insertion: superior angle of scapula toward the scapular spine |
| Action:
- elevates the scapula
- extends and/or laterally flexes the head
|
| Blood: transverse cervical artery |
| Nerve:
- nerves off cervical plexus, C3,4
- dorsal scapular nerve, C5
|
Rhomboid minor
| Origin:
- spinous process of C7 & T1
- ligamentum nuchae
- supraspinous ligament
|
| Insertion: medial margin of the scapula at the medial angle |
| Action: retract scapula |
| Blood:
- deep branch of transverse cervical artery, OR
- dorsal scapular artery
|
| Nerve: dorsal scapular nerve, C5, [C4] |
Rhomboid major
| Origin:
- spinous processes of T2-T5
- supraspinous ligament
|
| Insertion: medial scapula from the scapular spine to the inferior angle |
| Action: retract scapula |
| Blood:
- deep branch of transverse cervical artery, OR
- dorsal scapular artery
|
| Nerve: dorsal scapular nerve, C5 |
Serratus anterior
| Origin: fleshy slips from the outer surface of upper 8 or 9 ribs |
| Insertion: costal aspect of medial margin of the scapula |
| Action:
- protract scapula
- stabilize scapula
- assists in upward rotation
|
| Blood:
- lateral thoracic artery supplies the upper part
- thoracodorsal artery supplies the lower part
|
| Nerve: long thoracic nerve, C5,6,7 |
Deltoid
| Origin:
- lateral, anterior 1/3 of distal clavicle
- lateral boarder of the acromion
- scapular spine
|
| Insertion: deltoid tuberosity of humerus |
| Action:
- abducts arm
- flexion and medial rotation (anterior portion)
- extension and lateral rotation (posterior portion)
|
| Blood:
- posterior humeral circumflex artery
- deltoid branch of thoracoacromial artery
|
| Nerve: axillary nerve, C5,6 |
Supraspinatus
| Origin:
- supraspinous fossa
- muscle fascia
|
| Insertion: uppermost of three facets of the greater tubercle of humerus |
| Action:
- abduction of arm (first 15-20°)
- stabilizes glenohumeral joint
|
| Blood: suprascapular artery (poorly supplied) |
| Nerve: suprascapular nerve, C5,6 |
Infraspinatus
| Origin:
- infraspinous fossa
- muscle fascia
|
| Insertion: middle facet of greater tubercle of humerus |
| Action:
- external rotation of the humerus
- stabilizes the glenohumeral joint
|
| Blood:
- suprascapular artery
- scapular circumflex artery
|
| Nerve: suprascapular nerve, C5,6 |
Teres minor
| Origin: middle half of the scapula’s lateral margin |
| Insertion: lowest of three facets of the greater tubercle of humerus |
| Action:
- lateral rotation of the humerus
- stabilizes the glenohumeral joint
|
| Blood: scapular circumflex artery |
| Nerve: axillary nerve, C5,6 |
Teres major
| Origin: inferior, lateral margin of the scapula |
| Insertion: crest of lesser tubercle (just medial to the insertion of latissimus dorsi) |
| Action:
- assists in adduction of arm
- assists in medial rotation of arm
- assists in extension from an flexed position
|
| Blood: thoracodorsal artery |
| Nerve: lower subscapular nerve, C5,6 |
Subscapularis
| Origin: subscapular fossa |
| Insertion: lesser tubercle of humerus |
| Action:
- medial rotation of the humerus
- stabilizes the glenohumeral joint
|
| Blood: Branches of subscapular artery |
| Nerve: upper & lower subscapular nerves, C5,6 |
Deep Back Musculature
Splenius Muscles:
Splenius capitis
| Origin:
- lower portion of ligamentum nuchae
- spinous processes of C3-T3(4)
|
| Insertion:
- superior nuchal line
- mastoid process of temporal bone
|
| Action:
- bilateral contraction: extend head & neck
- unilateral contraction: rotate and laterally bend head & neck to the contracted
(same) side
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Splenius cervicis
| Origin: spinous process of T3-T6 |
| Insertion: posterior tubercles of transverse processes of C2-C4 |
| Action:
- bilateral contraction: extend head & neck
- unilateral contraction: rotate and laterally bend head & neck to the contracted
(same) side
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Erector Spinae Muscles
Iliocostalis lumborum
| Origin: common tendinous origin: (same for all lower erector spinae)
- sacrum
- iliac crest
- spinous processes of lower thoracic & most lumbar vertebrae
|
| Insertion: lower border of angles of ribs (5)6-12 |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Iliocostalis thoracis
| Origin: upper border of ribs 6-12 (medial to I. lumborum's insertion.) |
| Insertion: lower border of angles of ribs 1-6 (sometimes transverse process of C7) |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Iliocostalis cervicis
| Origin: angles of ribs 1-6 |
| Insertion: transverse processes of C4-C6 |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Longissimus thoracis
| Origin: common tendinous origin: (same for all lower erector spinae)
- sacrum
- iliac crest
- spinous processes of lower thoracic & most lumbar vertebrae
|
| Insertion:
- transverse processes of all thoracic vertebrae
- all ribs between tubercles and angles
- transverse processes of upper lumbar vertebrae
|
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Longissimus cervicis
| Origin: transverse processes of T1-T5(6) |
| Insertion: transverse processes of C2-C6 |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Longissimus capitis
| Origin:
- transverse and articular processes of middle and lower cervical vertebrae
- transverse processes of upper thoracic vertebrae
|
| Insertion: posterior aspect of mastoid process of temporal bone |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Spinalis thoracis
| Origin: common tendinous origin: (same for all lower erector spinae)
- sacrum
- iliac crest
- spinous processes of lower thoracic & most lumbar vertebrae
|
| Insertion: spinous processes T3(4)-T8(9) |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Spinalis cervicis
| Origin: spinous processes of C6-T2 |
| Insertion: spinous processes of C2 (and possibly extend to C3 or C4) |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Spinalis capitis
| Origin: spinous processes of lower cervical & upper thoracic vertebrae |
| Insertion: between superior & inferior nuchal lines of occipital bone |
| Action: (same for all erector spinae)
- bilateral:
- extension of vertebral column
- maintenance of erect posture (pneumonic = I Like Standing)
- stabilization of vertebral column during flexion, acting in contrast to abdominal
muscles and the action of gravity
- unilateral:
- lateral bend to same side
- rotation to same side
- opposite muscles contract eccentrically for stabilization
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Transversospinal Muscles
Semispinalis thoracis
| Origin: transverse processes of T6-T12 vertebrae |
| Insertion: spinous processes of upper thoracic & lower cervical vertebrae |
| Action:
- bilaterally extends vertebral column, especially head and neck
- controls lateral flexion to side opposite contraction (eccentric for stability)
- maintains head posture
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Semispinalis cervicis
| Origin: transverse processes of T1-T6 vertebrae and can go down to lower thoracic |
| Insertion: spinous processes of C2-T5(6) |
| Action:
- bilaterally extends vertebral column, especially head and neck
- controls lateral flexion to side opposite contraction (eccentric for stability)
- maintains head posture
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Semispinalis capitus
| Origin:
- transverse processes of T1-T6
- articular processes of C4-C7
|
| Insertion: between superior & inferior nuchal lines of occipital bone |
| Action:
- bilaterally extends vertebral column, especially head and neck
- controls lateral flexion to side opposite contraction (eccentric for stability)
- maintains head posture
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Multifidus
| Origin:
 | cervical region: from articular processes of lower cervical vertebrae |
| thoracic region: from transverse processes of all thoracic vertebrae |
| lumbar region:
- lower portion of dorsal sacrum
- PSIS
- deep surface of tendenous origin of erector spinae
- mamillary processes of all lumbar vertebrae
|
|
| Insertion: spinous process of all vertebrae extending from L5 - C2 (skipping 1-3
segments) |
| Action:
- bilaterally extends vertebral column
- controls lateral flexion to side opposite contraction (eccentric for stability)
- unilaterally rotate vertebral bodies (column) to opposite side
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Long rotators
| Origin: transverse process of one vertebra |
| Insertion: skips one vertebra to insert on the base of spinous process of vertebra above |
| Action:
- rotate to opposite side
- bilateral extension
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Short rotators
| Origin: transverse process of one vertebra |
| Insertion: base of spinous process of vertebra immediately above |
| Action:
- rotate to opposite side
- bilateral extension
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Segmental Muscles
Interspinalis
| Origin: spinous processes of each vertebra |
| Insertion: to the spinous process of vertebra immediately above |
| Action: extension of the vertebrae segments |
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
Intertransversi
| Origin: (A to A and B to B)
| cervical region:
- from the anterior tubercle of transverse process
- from the posterior tubercle of transverse process
|
| thoracic region: (poorly developed) |
| lumbar region:
- lateral aspect of the transverse process
- mamillary process
|
|
| Insertion:
| cervical region:
- to the anterior tubercle immediately above
- to the posterior tubercle immediately above
|
| thoracic region: (poorly developed) |
| lumber region:
- lateral aspect of the transverse process immediately above
- to the accessory process on the vertebra immediately above
|
|
| Action:
- laterally flexes each respective pair of vertebrae
- (also eccentric muscle contraction provides stability)
|
| Blood: muscular branches of the aorta |
| Nerve: dorsal rami of spinal nerves |
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