Glossary of Anatomy Chapter 10C: Posterior Trunk Muscles
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- Latissimus Dorsi
- Broad, flat, triangular muscle of the lower back
O: indirect attachment via lumbodorsal fascia into spines of lower six thoracic vertebrae, lumbar vertebrae, lower 3-4 ribs, and iliac crest
I: spirals around teres major to insert in floor of intertubercular groove of humerus
A: prime mover in arm (upper arm) extension
- Most superficial muscle of posterior thorax, flat and triangular in shape
O: occipital bone, ligamentum nuchae, and spines of C7/all thoracic vertebrae
I: a continuous insertion along acromion and spine of scapula and lateral third of clavicle
A: Stabilizes, raises, retracts, and rotates scapula
- Two rectangular muscles lying deep to trapezius and inferior to levator scapulae.
O: spinous processes of C7 and T1 and spinous processes of T2-T5
I: medial border of scapula
A; retract scapula, squaring shoulders
- Levator Scapulae
- Located at back and side of neck, deep to trapezius.
O: transverse processes of C1-C4
I: medial border of the scapula, superior to the spine
A: elevates/adducts scapula in concert with superior fibres of trapezius
- Forms part of posterior wall of axilla. A rotator cuff muscle.
O: subscapular fossa of scapula
I: lesser tubercle of humerus
A: chief medial rotator of humerus (pec major synergist)
- Located on posterior aspect of scapula, deep to trapezius. Rotator cuff muscle.
O: supraspinous fossa of scapula
I: superior part of greater tubercle of humerus
A: stabilizes shoulder joint (preventing downward dislocation)
- Scapular muscle partially covered by deltoid and trapezius. Rotator cuff muscle.
O: supraspinous fossa of scapula
I: greater tubercle of humerus posterior to insertion of supraspinatus
A: Helps to hold head of humerus in glenoid cavity.
- Teres Major
- Thick, rounded muscle located inferior to teres minor.
O: posterior surface of scapula at inferior angle.
I: intertubercular groove of the humerus
A: posteromedially extends, medially rotates, and adducts humerus (synergist of latissimus dorsi)
- Teres Minor
- Small, elongated muscle inferior to infraspinatus. Rotator cuff muscle.
O: Lateral border of dorsal scapular surface
I: greater tubercle of humerus inferior to infraspinatus insertion
A: helps to hold head of humerus in glenoid cavity (infraspinatus synergist)
- Small, cylindrical muscle.
O: coracoid process of scapula
I: medial surface of humerus shaft
A: Flexion and adduction of humerus. (Synergist of pec major)
- Erector Spinae
- Intermediate layer of intrinsic back muscles
O: ribs, transverse processes/spines of vertebrae
I: ribs, transverse processes/spines of vertebrae
A: Prime mover of back extension, lateral bending of back, maintaining posture
- Quadratus Lumbornum
- Fleshy muscle forming part of posterior abdominal wall.
O: iliac crest and lumbar fascia
I: transverse processes of upper lumbar vertebrae and lower margin of rib 12
A: flexes vertebral column laterally
- Composite muscle forming part of deep layer of intrinsic back muscles.
O: transverse processes of C7-T12
I: occipital bone and spinous processes of cervical vertebrae/T1-T4.
A: Extends vertebral column and head and rotates them to opposite sides. (Sternocleidomastoid synergist)
- Rotator Cuff
- Supraspinatus, infraspinatus, subscapularis, teres minor
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