Trunk, Front & Back Musculature

Muscle Regions of the Body:

• Head and neck
• Trunk, front and back
• Brachium, antibrachium & hand
• Thigh, leg & foot

• Superficial Back
• Pectoral
• Shoulder Girdle
• Deep Back
  • Splenius Muscles
  • Erector Spinae Muscles
  • Transversospinal Muscles
  • Segmental Muscles

Links Related to this Region:

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Superficial Back Musculature

Trapezius

• Origin:
  1. external occipital protuberance
  2. along the medial sides of the superior nuchal line
  3. ligamentum nuchae (surrounding the cervical spinous processes)
  4. spinous processes of C1-T12
• Insertion:
  1. posterior, lateral 1/3 of clavicle
  2. acromion
  3. superior spine of scapula
• Action:
  1. elevates scapula
  2. upward rotation of the scapula (upper fibers)
  3. downward rotation of the scapula (lower fibers)
  4. retracts scapula
• Blood: transverse cervical artery
• Nerve:
  1. spinal Accessory (XI) (efferent or motor fibers)
  2. ventral ramii of C3 & C4 (afferent or sensory fibers)

Latissimus dorsi

• Origin:
  1. spinous process of T7-L5
  2. upper 2-3 sacral segments
  3. iliac crest
  4. lower 3 or 4 Ribs
• Insertion: lateral lip of the intertubercular groove
• Action:
  1. adduction of humerus
  2. medial rotation of the humerus
  3. extension from flexed position
  4. 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:
  1. medial 1/3 of clavicle
  2. anterior aspect of manubrium & length of body of sternum
  3. cartilaginous attachments of upper 6 ribs
  4. external oblique's aponeurosis
• Insertion:
  1. lateral lip of bicipital groove to the crest of the greater tubercle
  2. clavicular fibers insert more distally; sternal fibers more proximally
• Action:
  1. adducts humerus
  2. medially rotates humerus
  3. flexion of the arm from extension (clavicular portion)
• Blood:
  1. pectoralis branch of thoracoacromial artery (runs with lateral pec. nerve)
  2. lateral thoracic artery (lesser supply, and runs with medial pectoral nerve)
• Nerve:
  1. lateral pectoral nerve, C5,6,7 to clavicular portion
  2. 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:
  1. depresses & downwardly rotates the scapula
  2. assists in scapular protraction from a retracted position
  3. 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:
  1. elevates the scapula
  2. extends and/or laterally flexes the head
• Blood: transverse cervical artery
• Nerve:
  1. nerves off cervical plexus, C3,4
  2. dorsal scapular nerve, C5

Rhomboid minor

• Origin:
  1. spinous process of C7 & T1
  2. ligamentum nuchae
  3. supraspinous ligament
• Insertion: medial margin of the scapula at the medial angle
• Action: retract scapula
• Blood:
  1. deep branch of transverse cervical artery, OR
  2. dorsal scapular artery
• Nerve: dorsal scapular nerve, C5, [C4]

Rhomboid major

• Origin:
  1. spinous processes of T2-T5
  2. supraspinous ligament
• Insertion: medial scapula from the scapular spine to the inferior angle
• Action: retract scapula
• Blood:
  1. deep branch of transverse cervical artery, OR
  2. 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:
  1. protract scapula
  2. stabilize scapula
  3. assists in upward rotation
• Blood:
  1. lateral thoracic artery supplies the upper part
  2. thoracodorsal artery supplies the lower part
• Nerve: long thoracic nerve, C5,6,7

Deltoid

• Origin:
  1. lateral, anterior 1/3 of distal clavicle
  2. lateral boarder of the acromion
  3. scapular spine
• Insertion: deltoid tuberosity of humerus
• Action:
  1. abducts arm
  2. flexion and medial rotation (anterior portion)
  3. extension and lateral rotation (posterior portion)
• Blood:
  1. posterior humeral circumflex artery
  2. deltoid branch of thoracoacromial artery
• Nerve: axillary nerve, C5,6

Supraspinatus

• Origin:
  1. supraspinous fossa
  2. muscle fascia
• Insertion: uppermost of three facets of the greater tubercle of humerus
• Action:
  1. abduction of arm (first 15-20°)
  2. stabilizes glenohumeral joint
• Blood: suprascapular artery (poorly supplied)
• Nerve: suprascapular nerve, C5,6

Infraspinatus

• Origin:
  1. infraspinous fossa
  2. muscle fascia
• Insertion: middle facet of greater tubercle of humerus
• Action:
  1. external rotation of the humerus
  2. stabilizes the glenohumeral joint
• Blood:
  1. suprascapular artery
  2. 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:
  1. lateral rotation of the humerus
  2. 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:
  1. assists in adduction of arm
  2. assists in medial rotation of arm
  3. 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:
  1. medial rotation of the humerus
  2. stabilizes the glenohumeral joint
• Blood: Branches of subscapular artery
• Nerve: upper & lower subscapular nerves, C5,6

Deep Back Musculature

Splenius Muscles:

Splenius capitis

• Origin:
  1. lower portion of ligamentum nuchae
  2. spinous processes of C3-T3(4)
• Insertion:
  1. superior nuchal line
  2. mastoid process of temporal bone
• Action:
  1. bilateral contraction: extend head & neck
  2. 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:
  1. bilateral contraction: extend head & neck
  2. 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

Iliocostalis lumborum

• Origin: common tendinous origin: (same for all lower erector spinae)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
• Insertion: lower border of angles of ribs (5)6-12
• Action: (same for all erector spinae)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
• Insertion:
  1. transverse processes of all thoracic vertebrae
  2. all ribs between tubercles and angles
  3. transverse processes of upper lumbar vertebrae
• Action: (same for all erector spinae)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. opposite muscles contract eccentrically for stabilization
• Blood: muscular branches of the aorta
• Nerve: dorsal rami of spinal nerves

Longissimus capitis

• Origin:
  1. transverse and articular processes of middle and lower cervical vertebrae
  2. transverse processes of upper thoracic vertebrae
• Insertion: posterior aspect of mastoid process of temporal bone
• Action: (same for all erector spinae)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
• Insertion: spinous processes T3(4)-T8(9)
• Action: (same for all erector spinae)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. 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)
  1. bilateral:
     1. extension of vertebral column
     2. maintenance of erect posture (pneumonic = I Like Standing)
     3. stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity
  2. unilateral:
     1. lateral bend to same side
     2. rotation to same side
     3. opposite muscles contract eccentrically for stabilization
• Blood: muscular branches of the aorta
• Nerve: dorsal rami of spinal nerves

Semispinalis thoracis

• Origin: transverse processes of T6-T12 vertebrae
• Insertion: spinous processes of upper thoracic & lower cervical vertebrae
• Action:
  1. bilaterally extends vertebral column, especially head and neck
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. 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:
  1. bilaterally extends vertebral column, especially head and neck
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. maintains head posture
• Blood: muscular branches of the aorta
• Nerve: dorsal rami of spinal nerves

Semispinalis capitus

• Origin:
  1. transverse processes of T1-T6
  2. articular processes of C4-C7
• Insertion: between superior & inferior nuchal lines of occipital bone
• Action:
  1. bilaterally extends vertebral column, especially head and neck
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. 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:
    1. lower portion of dorsal sacrum
    2. PSIS
    3. deep surface of tendenous origin of erector spinae
    4. mamillary processes of all lumbar vertebrae
• Insertion: spinous process of all vertebrae extending from L5 - C2 (skipping 1-3 segments)
• Action:
  1. bilaterally extends vertebral column
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. 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:
  1. rotate to opposite side
  2. 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:
  1. rotate to opposite side
  2. bilateral extension
• Blood: muscular branches of the aorta
• Nerve: dorsal rami of spinal nerves

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:
    1. from the anterior tubercle of transverse process
    2. from the posterior tubercle of transverse process
  • thoracic region: (poorly developed)
  • lumbar region:
    1. lateral aspect of the transverse process
    2. mamillary process
• Insertion:
  • cervical region:
    1. to the anterior tubercle immediately above
    2. to the posterior tubercle immediately above
  • thoracic region: (poorly developed)
  • lumber region:
    1. lateral aspect of the transverse process immediately above
    2. to the accessory process on the vertebra immediately above
• Action:
  1. laterally flexes each respective pair of vertebrae
  2. (also eccentric muscle contraction provides stability)
• Blood: muscular branches of the aorta
• Nerve: dorsal rami of spinal nerves

© 1998 by Darryl Hosford, all rights reserved.