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Anatomy 101

 

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Trunk, Front & Back Musculature

Muscle Regions of the Body:

bulletHead and neck
bulletTrunk, front and back
bulletBrachium, antibrachium & hand
bulletThigh, leg & foot

Muscle Groups within this Region:

bulletSuperficial Back
bulletPectoral
bulletShoulder Girdle
bulletDeep Back
bulletSplenius Muscles
bulletErector Spinae Muscles
bulletTransversospinal Muscles
bulletSegmental Muscles


Superficial Back Musculature

Trapezius

bulletOrigin:
  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
bulletInsertion:
  1. posterior, lateral 1/3 of clavicle
  2. acromion
  3. superior spine of scapula
bulletAction:
  1. elevates scapula
  2. upward rotation of the scapula (upper fibers)
  3. downward rotation of the scapula (lower fibers)
  4. retracts scapula
bulletBlood: transverse cervical artery
bulletNerve:
  1. spinal Accessory (XI) (efferent or motor fibers)
  2. ventral ramii of C3 & C4 (afferent or sensory fibers)


Latissimus dorsi

bulletOrigin:
  1. spinous process of T7-L5
  2. upper 2-3 sacral segments
  3. iliac crest
  4. lower 3 or 4 Ribs
bulletInsertion: lateral lip of the intertubercular groove
bulletAction:
  1. adduction of humerus
  2. medial rotation of the humerus
  3. extension from flexed position
  4. downward rotation of the scapula
bulletBlood: thoracodorsal artery
bulletNerve: thoracodorsal nerve, C6,7,8


Pectoral Musculature

 

Subclavius

bulletOrigin: first rib about the junction of bone and cartilage
bulletInsertion: lower surface of clavicle
bulletAction: assists in stabilizing the clavicle
bulletBlood: clavicular branch of thoracoacromial artery
bulletNerve: nerve to the subclavius, C5,6


Pectoralis major

bulletOrigin:
  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
bulletInsertion:
  1. lateral lip of bicipital groove to the crest of the greater tubercle
  2. clavicular fibers insert more distally; sternal fibers more proximally
bulletAction:
  1. adducts humerus
  2. medially rotates humerus
  3. flexion of the arm from extension (clavicular portion)
bulletBlood:
  1. pectoralis branch of thoracoacromial artery (runs with lateral pec. nerve)
  2. lateral thoracic artery (lesser supply, and runs with medial pectoral nerve)
bulletNerve:
  1. lateral pectoral nerve, C5,6,7 to clavicular portion
  2. medial pectoral nerve, C8,T1 to sternal portion


Pectoralis minor

bulletOrigin: outer surface of ribs 2-5 or 3-5 or 6
bulletInsertion: medial aspect of coracoid process of the scapula
bulletAction:
  1. depresses & downwardly rotates the scapula
  2. assists in scapular protraction from a retracted position
  3. stabilizes the scapula
bulletBlood: lateral thoracic artery
bulletNerve: medial pectoral nerve, C8,T1


Shoulder Girdle Musculature

 

Levator scapulae

bulletOrigin: transverse processes of C1-C3 or C4
bulletInsertion: superior angle of scapula toward the scapular spine
bulletAction:
  1. elevates the scapula
  2. extends and/or laterally flexes the head
bulletBlood: transverse cervical artery
bulletNerve:
  1. nerves off cervical plexus, C3,4
  2. dorsal scapular nerve, C5


Rhomboid minor

bulletOrigin:
  1. spinous process of C7 & T1
  2. ligamentum nuchae
  3. supraspinous ligament
bulletInsertion: medial margin of the scapula at the medial angle
bulletAction: retract scapula
bulletBlood:
  1. deep branch of transverse cervical artery, OR
  2. dorsal scapular artery
bulletNerve: dorsal scapular nerve, C5, [C4]


Rhomboid major

bulletOrigin:
  1. spinous processes of T2-T5
  2. supraspinous ligament
bulletInsertion: medial scapula from the scapular spine to the inferior angle
bulletAction: retract scapula
bulletBlood:
  1. deep branch of transverse cervical artery, OR
  2. dorsal scapular artery
bulletNerve: dorsal scapular nerve, C5


Serratus anterior

bulletOrigin: fleshy slips from the outer surface of upper 8 or 9 ribs
bulletInsertion: costal aspect of medial margin of the scapula
bulletAction:
  1. protract scapula
  2. stabilize scapula
  3. assists in upward rotation
bulletBlood:
  1. lateral thoracic artery supplies the upper part
  2. thoracodorsal artery supplies the lower part
bulletNerve: long thoracic nerve, C5,6,7


Deltoid

bulletOrigin:
  1. lateral, anterior 1/3 of distal clavicle
  2. lateral boarder of the acromion
  3. scapular spine
bulletInsertion: deltoid tuberosity of humerus
bulletAction:
  1. abducts arm
  2. flexion and medial rotation (anterior portion)
  3. extension and lateral rotation (posterior portion)
bulletBlood:
  1. posterior humeral circumflex artery
  2. deltoid branch of thoracoacromial artery
bulletNerve: axillary nerve, C5,6


Supraspinatus

bulletOrigin:
  1. supraspinous fossa
  2. muscle fascia
bulletInsertion: uppermost of three facets of the greater tubercle of humerus
bulletAction:
  1. abduction of arm (first 15-20°)
  2. stabilizes glenohumeral joint
bulletBlood: suprascapular artery (poorly supplied)
bulletNerve: suprascapular nerve, C5,6


Infraspinatus

bulletOrigin:
  1. infraspinous fossa
  2. muscle fascia
bulletInsertion: middle facet of greater tubercle of humerus
bulletAction:
  1. external rotation of the humerus
  2. stabilizes the glenohumeral joint
bulletBlood:
  1. suprascapular artery
  2. scapular circumflex artery
bulletNerve: suprascapular nerve, C5,6


Teres minor

bulletOrigin: middle half of the scapula’s lateral margin
bulletInsertion: lowest of three facets of the greater tubercle of humerus
bulletAction:
  1. lateral rotation of the humerus
  2. stabilizes the glenohumeral joint
bulletBlood: scapular circumflex artery
bulletNerve: axillary nerve, C5,6


Teres major

bulletOrigin: inferior, lateral margin of the scapula
bulletInsertion: crest of lesser tubercle (just medial to the insertion of latissimus dorsi)
bulletAction:
  1. assists in adduction of arm
  2. assists in medial rotation of arm
  3. assists in extension from an flexed position
bulletBlood: thoracodorsal artery
bulletNerve: lower subscapular nerve, C5,6


Subscapularis

bulletOrigin: subscapular fossa
bulletInsertion: lesser tubercle of humerus
bulletAction:
  1. medial rotation of the humerus
  2. stabilizes the glenohumeral joint
bulletBlood: Branches of subscapular artery
bulletNerve: upper & lower subscapular nerves, C5,6


Deep Back Musculature

 

Splenius Muscles:


Splenius capitis

bulletOrigin:
  1. lower portion of ligamentum nuchae
  2. spinous processes of C3-T3(4)
bulletInsertion:
  1. superior nuchal line
  2. mastoid process of temporal bone
bulletAction:
  1. bilateral contraction: extend head & neck
  2. unilateral contraction: rotate and laterally bend head & neck to the contracted (same) side
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Splenius cervicis

bulletOrigin: spinous process of T3-T6
bulletInsertion: posterior tubercles of transverse processes of C2-C4
bulletAction:
  1. bilateral contraction: extend head & neck
  2. unilateral contraction: rotate and laterally bend head & neck to the contracted (same) side
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Erector Spinae Muscles


Iliocostalis lumborum

bulletOrigin: common tendinous origin: (same for all lower erector spinae)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
bulletInsertion: lower border of angles of ribs (5)6-12
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Iliocostalis thoracis

bulletOrigin: upper border of ribs 6-12 (medial to I. lumborum's insertion.)
bulletInsertion: lower border of angles of ribs 1-6 (sometimes transverse process of C7)
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Iliocostalis cervicis

bulletOrigin: angles of ribs 1-6
bulletInsertion: transverse processes of C4-C6
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Longissimus thoracis

bulletOrigin: common tendinous origin: (same for all lower erector spinae)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
bulletInsertion:
  1. transverse processes of all thoracic vertebrae
  2. all ribs between tubercles and angles
  3. transverse processes of upper lumbar vertebrae
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Longissimus cervicis

bulletOrigin: transverse processes of T1-T5(6)
bulletInsertion: transverse processes of C2-C6
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Longissimus capitis

bulletOrigin:
  1. transverse and articular processes of middle and lower cervical vertebrae
  2. transverse processes of upper thoracic vertebrae
bulletInsertion: posterior aspect of mastoid process of temporal bone
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Spinalis thoracis

bulletOrigin: common tendinous origin: (same for all lower erector spinae)
  1. sacrum
  2. iliac crest
  3. spinous processes of lower thoracic & most lumbar vertebrae
bulletInsertion: spinous processes T3(4)-T8(9)
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Spinalis cervicis

bulletOrigin: spinous processes of C6-T2
bulletInsertion: spinous processes of C2 (and possibly extend to C3 or C4)
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Spinalis capitis

bulletOrigin: spinous processes of lower cervical & upper thoracic vertebrae
bulletInsertion: between superior & inferior nuchal lines of occipital bone
bulletAction: (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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Transversospinal Muscles


Semispinalis thoracis

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


Semispinalis cervicis

bulletOrigin: transverse processes of T1-T6 vertebrae and can go down to lower thoracic
bulletInsertion: spinous processes of C2-T5(6)
bulletAction:
  1. bilaterally extends vertebral column, especially head and neck
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. maintains head posture
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Semispinalis capitus

bulletOrigin:
  1. transverse processes of T1-T6
  2. articular processes of C4-C7
bulletInsertion: between superior & inferior nuchal lines of occipital bone
bulletAction:
  1. bilaterally extends vertebral column, especially head and neck
  2. controls lateral flexion to side opposite contraction (eccentric for stability)
  3. maintains head posture
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Multifidus

bulletOrigin:
bulletcervical region: from articular processes of lower cervical vertebrae
bulletthoracic region: from transverse processes of all thoracic vertebrae
bulletlumbar 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
bulletInsertion: spinous process of all vertebrae extending from L5 - C2 (skipping 1-3 segments)
bulletAction:
  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
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Long rotators

bulletOrigin: transverse process of one vertebra
bulletInsertion: skips one vertebra to insert on the base of spinous process of vertebra above
bulletAction:
  1. rotate to opposite side
  2. bilateral extension
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Short rotators

bulletOrigin: transverse process of one vertebra
bulletInsertion: base of spinous process of vertebra immediately above
bulletAction:
  1. rotate to opposite side
  2. bilateral extension
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Segmental Muscles


Interspinalis

bulletOrigin: spinous processes of each vertebra
bulletInsertion: to the spinous process of vertebra immediately above
bulletAction: extension of the vertebrae segments
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves


Intertransversi

bulletOrigin: (A to A and B to B)
bulletcervical region:
  1. from the anterior tubercle of transverse process
  2. from the posterior tubercle of transverse process
bulletthoracic region: (poorly developed)
bulletlumbar region:
  1. lateral aspect of the transverse process
  2. mamillary process
bulletInsertion:
bulletcervical region:
  1. to the anterior tubercle immediately above
  2. to the posterior tubercle immediately above
bulletthoracic region: (poorly developed)
bulletlumber region:
  1. lateral aspect of the transverse process immediately above
  2. to the accessory process on the vertebra immediately above
bulletAction:
  1. laterally flexes each respective pair of vertebrae
  2. (also eccentric muscle contraction provides stability)
bulletBlood: muscular branches of the aorta
bulletNerve: dorsal rami of spinal nerves