-
Rectus abdominus: straight-abdomen
Action: flex and rotate lumbar region of vertebral column; fix and depress ribs; stabilize pelvis during walking
- O: pubic crest and symphysis
- I: xiphoid process and costal cartilages of ribs 5-7
-
External oblique: toward outside- running at an angle
Action: pair contracts to aid in flexion of vertebral column; individually aid back muscles in trunk rotation/ lateral flexion
- O: by fleshy strips from outer surfaces of lower eight ribs
- I: most fibers insert anteriorly into linea alba, some onto pubic crest, pubic tubercle, and iliac crest
-
Internal oblique: deep- running at an angle
Action: flexing vertebral column; aid muscles of back in trunk rotation and lateral flexion
- O: lumbar fascia, iliac crest, and inguinal ligament
- I: linea alba, pubic crest, last 3-4 ribs, and costal margin
-
Transversus abdominus: running straight across- abdomen
Action: compresses abdominal contents
- O: inguinal ligament, lumbar fascia, cartilages of last 6 ribs; iliac crest
- I: linea alba, pubic crest
-
Pectoral minor: chest- lesser
Action: draws scapula forward and downward with ribs fixed; with scapula fixed, draws rib cage superiorly
- O: anterior surfaces of ribs 3-5 or 2-4
- I: coracoid process of scapula
-
Serratus anterior: saw
Action: prime mover to protract and hold scapula against chest wall; rotates scapula to move laterally and upward; important role in abduction and raising of arm
- O: a series of muscle slips from ribs 1-8 (or 9)
- I: entire anterior surface of vertebral border of scapula
-
Subclavius: beneath-clavicle
Action: helps stabilize and depress pectoral girdle
- O: costal cartilage of rib 1
- I: groove on inferior surface of clavicle
-
Trapezius: irregular four-sided figure
Action: stabilizes, raises, retracts, and rotates scapula; middle fibers retract (adduct) scapula; superior fibers elevate or extend head when scapula is fixed; inferior fibers depress
- O: occipital bone, nuchal ligament, and spines of C7 and all thoracic vertebrae
- I: a continuous insertion along acromion and spine of scapula and lateral third of clavicle
-
Levator scapulae: raises- scapula
Action: elevates adducts scapula in concert with superior fibers of trapezius
- O: transverse processes of C1-C4
- I: medial border of scapula, superior to the spine
-
Rhomboids: diamond shaped
major, minor
Action: retracts scapula- squaring shoulders; stabilizes scapula
- O: spinous processes of C7 and T1 (minor); spinous processes of T2-T5 (major)
- I: medial border of scapula
-
Pectoralis major: chest- larger
Action: prime mover of arm flexion; rotates arm medially; adducts arm against resistance; pulls ribcage upward to aid in forced respiration
- O: sternal end of clavicle, sternum cartilage of ribs 1-6 (or 7), and aponeurosis of external oblique muscle
- I: fibers converge to insert by a short tendon into intertubercular groove of humerus
-
Latissimus dorsi: widest- back
Action: prime mover of arm extension; arm adductor; medially rotates arm at shoulder; depresses scapula
- O: indirect attachment via lumbodorsal fascia into spines of lower six thoracic vertebrae, lumbar vertebrae, lower ribs 3-4, and iliac crest
- I: spirales around teres major to insert in floor of intertubercular groove of humerus
-
Deltoid: triangular
Action: prime mover of arm abduction; when all fibers are active- antagonist to pectoralis major and latissimus dorsi; when anterior fibers are active acts in flexion and medial rotation of humerus therefore synergist to pectoralis major; posterior fibers effects extension and lateral rotation of arm
- O: embraces insertion of trapezius: lateral third of clavicle; acromium and spine of scapula
- I: deltoid tuberosity of humerus
-
Subscapularis: under- scapula
Action: chief medial rotator of humerus; stabilizes shoulder joint
- O: subscapular fossa of scapula
- I: lesser tubercle of humerus
-
Supraspinatus: above- spine
Action: stabilizes shoulder joint; assists in abduction of arm
- O: supraspinous fossa of scapula
- I: superior part of greater tubercle of humerus
-
Infraspinatous: below- spine
Action: stabilizes shoulder joint; rotates humerus laterally
- O: infraspinous fossa of scapula
- I: greater tubercle of humerus
-
Teres minor: round- lesser
Action: stabilizes shoulder joint; rotates humerus laterally; adducts arm
- O: lateral border of dorsal scapular surface
- I: greater tubercle of humerus
-
Teres major: round- greater
Action: posteromedially extends, medially rotates, and adducts humerus; synergist of latissimus dorsi
- O: posterior surface of scapula at inferior angle
- I : intertubercular groove of humerus; insertion tendon fused with that of latissumus dorsi
-
Coracobrachialis: arm
Action: flexion and adduction of the humerus; synergist of pectoralis major
- O: coracoid process of scapula
- I: medial surface of humerus shaft
|
|
