Set 2: Muscles of trunk and arms

Muscles of Respiration• Breathing requires the use of muscles– diaphragm– external intercostal muscles– internal intercostal muscles

• Contraction of the first 2 produces Inspiration• Contraction of the last produces Forced Expiration• Normal Expiration requires little muscular activity– elastic recoil of tissues and gravity collapsing the chest– only inspiratory muscles active in braking action, so

exhalation is smooth

Muscles of Respiration -- Diaphragm

• Muscular dome between thoracic and abdominal cavities

• Muscle fascicles extend to a fibrous central tendon

• Contraction flattens it– increases the vertical dimension of the thorax drawing air into

the lungs– raises the abdominal pressure to help expel urine, feces and

facilitating childbirth

Central tendon

Muscles of Respiration -- Intercostals

• External intercostals– extend downward and anteriorly

from rib to rib– pull ribcage up & outward during

inspiration

• Internal intercostals– extend upward and anteriorly

from rib to rib– pull ribcage downward during

forced expiration

Muscles of the Abdomen• 4 Pairs of sheetlike muscles– external oblique– internal oblique– transverse abdominis– rectus abdominis

• Functions– support the viscera– stabilize the vertebral column– help in respiration, urination, defecation & childbirth

Rectus Abdominis & External Oblique• External

oblique– superficial– downward – anteriorly– inguinal

ligament

• Rectus abdominis– vertical,

straplike– tendinous

intersections– rectus sheath– linea alba

External oblique Rectus abdominis

Internal Oblique -Transverse Abdominis

• Internal oblique– anteriorly– upwards

• Transverse abdominis– horizontal fiber

orientation– deepest layer

Transverse abdominisInternal oblique

Superficial Muscles of the Back

Trapezius

Latissimus dorsi

SemispinalisSplenius

Levator scapulaeRhomboideusSupraspinatusInfraspinatusTeres major

Gluteus maximusGluteus medius

Anterior Scapular Muscle Group• Pectoralis Minor– ribs 3-5 to coracoid

process of scapula– protracts &

depresses scapula– lifts ribs during

forced expiration

• Serratus Anterior– ribs 1-9 to medial

border of scapula– abducts & rotates

or depresses scapula

– throwing muscle

Muscles Acting on the Scapula

Posterior Scapular Muscle Group

• 4 Muscles – superficial = Trapezius– deep = Rhomboids & Levator scapulae

• Trapezius– rotate scapula upward– retract scapula– depress scapula

• With Levator scapulae & Rhomboids elevates scapula

• With Serratus anterior depresses scapula

• Rhomboideus mm.– medial border of

scapula to C7-T1

Posterior Scapular Muscle Group

• Levator scapulae– from superior angle

of scapula to C1-C4

Muscles Acting on the Humerus• 9 Muscles cross the shoulder joint to the humerus– 2 axial muscles arise from axial skeleton– prime movers of humerus in flexion & extension– arise from sternum & clavicle OR T7-L5 & ilium

Pectoralis major Latissimus dorsi

• 7 scapular muscles arise from scapula

– Deltoid is prime mover• flexion, extension and

abduction of humerus

– Coracobrachialis assists in flexion

– Teres major assists in extension

– Remaining 4 form the rotator cuff muscles that reinforce the shoulder joint capsule

Muscles Acting on the Humerus

Posterior View of Chest in Cadaver

Rotator Cuff Muscles• Extending from

posterior scapula to humerus – supraspinatus– infraspinatus – teres Minor

• Extending from anterior scapula to humerus – subscapularis

All 4 help reinforce joint capsule.

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

Anterior View of Chest in Cadaver

Muscles Acting on the Elbow• Principal flexors – biceps brachii • inserts on radius

– brachialis • inserts on ulna

• Synergistic flexor– brachioradialis

• Prime extensor– triceps brachii• inserts onto ulna

CS Through Upper Limb & Forearm

Supination & Pronation of the Forearm

Supination• Supinator muscle• Palm facing anteriorly

Pronation• Pronator teres and Pronator

quadratus mm.• Palm faces posteriorly