SJSU SP24 BIOL-65 Chapter 12: The Muscle System - Appendicular Musculature

Muscles Acting on the Arm

Pectoralis major, Deltoid, Coracobrachialis, Teres major, Latissimus Dorsi

Pectoralis major

Actions of the Pectoralis Major

Flexes, adducts, and medially rotates humerus, as in climbing or hugging; aids in deep inspiration

Skeletal attachments of the Pectoralis Major

Medial half of clavicle; lateral margin of sternum; costal cartilages 1-7; aponeurosis of external oblique; lateral lip of intertubercular sulcus of humerus

Innervation of the Pectoralis Major

Medial and lateral pectoral nerves

Deltoid

Actions of the Deltoid

Anterior fibers flex and medially rotate arm; lateral fibers abduct arm; posterior fibers extend and laterally rotate arm; involved in arm swinging during such actions as walking or bowling, and in adjustment of hand height for various manual tasks

Skeletal Attachments of the Deltoid

Acromion and spine of scapula; clavicle; deltoid tuberosity of humerus

Innervation of the Deltoid

Axillary nerve

Coracobrachialis

Actions of the Coracobrachialis

Flexes and medially rotates arm; resists deviation of arm from frontal plane during abduction

Skeletal Attachments of the Coracobrachialis

Coracoid process of scapula; medial aspect of humeral shaft

Innervation of the Coracobrachialis

Musculocutaneous nerve

Teres major

extends and medially rotates humerus

Actions of the Teres Major

Extends and medially rotates humerus; contributes to arm swinging

Skeletal Attachments of the Teres Major

Inferior angle of scapula; medial lip of intertubercular sulcus of humerus

Innervation of the Teres Major

Lower subscapular nerve

Latissimus dorsi

adducts and medially rotates humerus, extends shoulder joint

Actions of the Latissimus Dorsi

Adducts and medially rotates humerus; extends the shoulder joint as in pulling on oars of a rowboat; produces backswing of arm in such actions as walking or bowling; with hands grasping overhead objects, pulls body forward and upward, as in climbing; produces strong downstrokes of an arm as in hammering and swimming (nicknamed the "swimmer's muscle"); aids in deep inspiration, sudden expiration as in sneezing and coughing, and prolonged forceful expiration as in singing or playing a wind instrument

Skeletal Attachments of the Latissimus Dorsi

Vertebrae T7-L5; lower three or four ribs; iliac crest; thoracolumbar fascia; Floor of intertubercular sulcus of humerus

Innervation of the Latissimus Dorsi

Thoracodorsal Nerve

Rotator cuff (SITS) muscles

Supraspinatus, infraspinatus, teres minor, subscapularis

Supraspinatus

Actions of the Supraspinatus

Aids deltoid in abduction of arm; resists downward slippage of humeral head when arm is relaxed or when carrying weight

Skeletal Attachments of the Supraspinatus

Supraspinous fossa of scapula; greater tubercle of humerus

Innervation of the Supraspinatus

Suprascapular nerve

Infraspinatus

Actions of the Infraspinatus

Modulates action of deltoid, preventing humeral head from sliding upward; laterally rotates humerus

Skeletal Attachments of the Infraspinatus

Infraspinous fossa of scapula; Greater tubercule of humerus

Innervation of the Infraspinatus

Suprascapular nerve

Teres minor

Actions of the Teres Minor

Modulates action of deltoid, preventing humeral head from sliding upward as arm is abducted; adducts and laterally rotates humerus

Skeletal Attachments of the Teres Minor

Lateral border and adjacent posterior surface of scapula; Greater tubercle of humerus; posterior surface of joint capsule

Innervation of the Teres Minor

Axillary nerve

Subscapularis

Actions of the Subscapularis

Modulates action of deltoid, preventing humeral head from sliding upward as arm is abducted; medially rotates humerus

Skeletal Attachments of the Subscapularis

Subnscapular fossa of scapula; Lesser tubercle of humerus; anterior surface of joint capsule

Innervation of the Subscapularis

Upper and lower subscapular nerves

Muscles Acting on the Forearm

Brachialis, biceps brachii, brachioradialis, Triceps brachii

Brachialis

Actions of the Brachialis

Prime mover of elbow flexion

Skeletal Attachments of the Brachialis

Anterior surface of distal half of humerus; coronoid process and tuberosity of ulna

Innervation of the Brachialis

Musculocutaneous nerve, radial nerve

Biceps brachii

Actions of the Biceps Brachii

Rapid or forceful supination of forearm; synergist in elblow flexion; slight shoulder flexion; tendon of long head stabilizes shoulder by holding humeral head against glenoid cavity

Skeletal Attachments of the Biceps Brachii

Long head--superior margin of glenoid cavity; Short head--coracoid process; Tuberosity of radius; fascia of forearm

Innervation of Biceps Brachii

Musculocutaneous nerve

Brachioradialis

Actions of the Brachioradialis

Flexes elbow

Skeletal Attachments of the Brachioradialis

Lateral supracondylar ridge of humerus; lateral surface of radius near styloid process

Innervation of the Brachioradialis

Radial nerve

Triceps brachii

Actions of the Triceps Brachii

Extends elbow; long head extends and adducts humerus

Skeletal Attachments of the Triceps Brachii

Long head--inferior margin of glenoid cavity and joint capsule; Lateral head--posterior surface of proximal end of humerus; medial head--posterior surface of entire humeral shaft

Innervation of the Triceps Brachii

Radial nerve

Supinator

Actions of the Supinator

Supinates forearm, as in turning a doorknob or driving a screw into wood with the right hand

Skeletal Attachments of the Supinator

Lateral epicondyle of humerus; supinator crest and fossa of ulna just distal to radial notch; anular and radial collateral ligaments of elbow; proximal one third of radius

Innervation of the Supinator

Radial nerve

Pronator teres

Actions of the Pronator Teres

Assists pronator quadratus in pronation, but only in rapid or forceful action; weakly flexes elbow

Skeletal Attachments of the Pronator Teres

Humeral shaft near medial epicondyle; coronoid process of ulna; lateral surface of radial shaft

Innervation of the Pronator Teres

Median nerve

Pronator quadratus

Actions of the Pronator Quadratus

Prime mover of forearm pronation; also resists separation of radius and ulna when force is applied to forearm through wrist, as in doing push-ups

Skeletal Attachments of the Pronator Quadratus

Anterior surface of distal ulna; anterior surface of distal radius

Innervation of the Pronator Quadratus

Median nerve

Muscles of the Forearm (Anterior)

Anterior compartment muscles flex the wrist (carpus), fingers (digits), and thumb (pollex)

Muscles of the Forearm (Posterior)

Posterior compartment muscles extend the wrist, fingers, and thumb

Muscles That Act on the Hip and Femur

Ilacus, Psoas major, adductor magnus, adductor brevis, adductor longus, and pectineus

Iliopsoas

consists of the Ilacus and Psoas major; flex the thigh

Ilacus

Actions of the Ilacus

Flexes thigh at hip when trunk is fixed, as in stair climbing; flexes trunk at hip when thigh is fixed; as in bending forward in a chair of sitting up in bed; balances trunk during sitting

Skeletal Attachments of the Ilacus

Iliac crest and fossa; superolateral region of sacrum; anterior sacroiliac and iliolumbar ligaments; lesser trochanter and nearby shaft of femur

Innervation of the Ilacus

Femoral nerve

Psoas major

Actions of the Psoas major

Same as Iliacus

Skeletal Attachments of the Psoas Major

Bodies and intervertebral discs of vertebrae T12-L5; transverse processes of lumbar vertebrae; Lesser trochanter and nearby shaft of femur

Innervation of the Psoas Major

Anterior rami of lumbar spinal nerves

Adductor magnus

Actions of the Adductor Magnus

Adducts and medially rotates thigh; extends thigh at hip

Skeletal Attachments of the Adductor Magnus

Inferior ramus of pubis; ramus and tuberosity of ischium; Linea aspera, gluteal tuberosity, and medial supracondylar line of femur

Innervation of the Adductor Magnus

Obtruator nerve; tibial nerve

Adductor brevis

Actions of the Adductor Brevis

Adducts thigh

Skeletal Attachments of the Adductor Brevis

Body and inferior ramus of pubis; Liena aspera and spiral line of femur

Innervation of the Adductor Brevis

Obturator nerve

Adductor longus

Actions of the Adductor Longus

Adducts and medially rotates thigh; flexes thigh at hip

Skeletal Attachments of the Adductor Longus

Body and inferior ramus of pubis; Linea aspera of femur

Innervation of the Adductor Longus

Obturator nerve

Pectineus

Actions of the Pectineus

Flexes and adducts thigh

Skeletal Attachments of the Pectineus

Superior ramus of pubis; spiral line of femur

Innervation of the Pectineus

Femoral nerve

Anterior Muscles of the Thigh

Quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), Sartorius

Quadriceps femoris

Actions of the Quadriceps Femoris

Extends the knee, as in kicking a ball and rising from a chair, in addition to actions of individual heads noted below

Skeletal Attachments of the Quadriceps Femoris

Varies; Patella; tibial tuberosity; lateral and medial condyles of tibia

Innervation of the Quadriceps Femoris

Femoral nerve