Muscles 1 OIA

Question 1

Pectoralis minor

Answer 1

Origin: Ribs 3-5 and overlying fascia

Insertion: Coracoid process of scapula

Action: Draws scapula laterally and forward around chest wall; rotates scapula and depresses apex of shoulder

Question 2

Serratus anterior

Answer 2

Origin: All or nearly all ribs

Insertion: Medial border of scapula

Action: Draws scapula laterally and forward around chest wall; protracts scapula; aids in rotating scapula to elevate apex of shoulder; fixes scapula during abduction of arm

Question 3

Trapezius

Answer 3

Origin: External occipital protuberance, medial 1/3 of superior nuchal line, nuchal ligament, lateral 1/3 of clavicle anterior rami of C3-C4 spinous processes of vertebrae C7-T3 or T4

Insertion: Acromion and spine of scapula, lateral 1/3 of clavicle

Action: Stabilizes scapula and shoulder during arm movements; elevates and depresses apex of shoulder; rotate and retract scapula

Question 4

Levator scapulae

Answer 4

Origin: Transverse processes of vertebrae C1-C4

Insertion: Superior angle to medial border of scapula

Action: Elevates scapula if cervical vertebrae are fixed; flexes neck laterally if scapula is fixed; retracts scapula and braces shoulder; rotates scapula and depresses apex of shoulder

Question 5

Rhomboid major

Answer 5

Origin: Spinous processes of vertebrae T2-T5

Insertion: Medial border of scapula

Action: Retracts scapula and braces shoulder; fixes scapula during arm movements

Question 6

Rhomboid minor

Answer 6

Origin: Spinous processes of vertebrae C7-T1, nuchal ligament

Insertion: Medial border of scapula

Action: Retracts scapula and braces shoulder; fixes scapula during arm movements

Question 7

Pectoralis major

Answer 7

Origin: Medial half of clavicle, costal cartilages 1-7, aponeurosis of external oblique

Insertion: Lateral lip of intertubercular sulcus of humerus

Action: Flexes, adducts, and medially rotates humerus; Aids in deep inspiration.

Question 8

Latissimus dorsi

Answer 8

Origin: Vertebrae T7-L5, lower three or four ribs, iliac crest, thoracolumbar fascia

Insertion: Floor of intertubercular sulcus of humerus

Action: Adducts and medially rotates humerus; extends the shoulder joint; pulls body forward and upward, as in climbing; aids in deep inspiration

Question 9

Deltoid

Answer 9

Origin: Acromion and spine of scapula; clavicle

Insertion: Deltoid tuberosity of humerus

Action: Anterior fibers flex and medially rotate arm; lateral fibers abduct arm; posterior fibers extend and laterally rotate arm

Question 10

Supraspinatus

Answer 10

Origin: Supraspinous fossa of scapula

Insertion: Greater tubercle of humerus

Action: Aids deltoid in abduction of arm; resists downward slippage of humeral head

Question 11

Infraspinatus

Answer 11

Origin: Infraspinous fossa of scapula

Insertion: Greater tubercle of humerus

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

Question 12

Teres major

Answer 12

Origin: Inferior angle of scapula

Insertion: Medial lip of intertubercular sulcus of humerus

Action: Extends and medially rotates humerus

Question 13

Teres minor

Answer 13

Origin: Lateral border and adjacent posterior surface of scapula

Insertion: Greater tubercle of humerus; posterior surface of joint capsule

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

Question 14

Subscapularis

Answer 14

Origin: Subscapular fossa of scapula

Insertion: Lesser tubercle of humerus, anterior surface of joint capsule

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

Question 15

Coracobrachialis

Answer 15

Origin: Coracoid process

Insertion: Medial aspect of humeral shaft

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

Question 16

Biceps brachii, short head

Answer 16

Origin: coracoid process

Insertion: Tuberosity of radius, fascia of forearm

Action: Rapid or forceful supination of forearm; synergist in elbow flexion; slight shoulder flexion

Question 17

Biceps brachii, long head

Answer 17

Origin: superior margin of glenoid cavity

Insertion: Tuberosity of radius, fascia of forearm

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

Question 18

Brachialis

Answer 18

Origin: Anterior surface of distal half of humerus

Insertion: Coronoid process and tuberosity of ulna

Action: Prime mover of elbow flexion

Question 19

Brachioradialis

Answer 19

Origin: Lateral supracondylar ridge of humerus

Insertion: Lateral surface of radius near styloid process

Action: Flexes elbow

Question 20

Triceps brachii, lateral head

Answer 20

Origin: posterior surface of proximal end of humerus

Insertion: Olecranon, fascia of forearm

Action: Extends elbow

Question 21

Triceps brachii, long head

Answer 21

Origin: inferior margin of glenoid cavity and joint capsule

Insertion: Olecranon, fascia of forearm

Action: Extends elbow; long head extends and adducts humerus

Question 22

Triceps brachii, medial head

Answer 22

Origin: posterior surface of entire humeral shaft

Insertion: Olecranon, fascia of forearm

Action: Extends elbow

Question 23

Anconeus

Answer 23

Origin: Lateral epicondyle of humerus

Insertion: Olecranon and posterior surface of ulna

Action: Extends elbow; may help to control ulnar movement during pronation

Question 24

Pronator quadratus

Answer 24

Origin: Anterior surface of distal ulna

Insertion: Anterior surface of distal radius

Action: Prime mover of forearm pronation; also resists separation of radius and ulna

Question 25

Pronator teres ## Footnote

Answer 25

**Origin:** Humeral shaft near medial epicondyle; coronoid process of ulna **Insertion:** Lateral surface of radial shaft **Action:** Assists pronator quadratus in pronation, but only in rapid or forceful action; weakly flexes elbow

Question 26

Supinator

Answer 26

**Origin:** Lateral epicondyle of humerus; supinator crest and fossa of ulna just distal to radial notch; anular and radial collateral ligaments of elbow **Insertion:** Proximal 1/3 of radius **Action:** Supinates forearm

Question 27

Flexor carpi radialis

Answer 27

**Origin:** Medial epicondyle of humerus **Insertion:** Base of metacarpals II-III **Action:** Flexes wrist anteriorly; aids in radial flexion of wrist

Question 28

Flexor carpi ulnaris ## Footnote

Answer 28

**Origin:** Medial epicondyle of humerus; medial margin of olecranon; posterior surface of ulna **Insertion:** Pisiform, hamate, metacarpal V **Action:** Flexes wrist anteriorly; aids in ulnar flexion of wrist

Question 29

Palmaris longus

Answer 29

**Origin:** Medial epicondyle of humerus **Insertion:** Flexor retinaculum, palmar aponeurosis **Action:** Anchors skin and fascia of palmar region; resists shearing forces when stress is applied to skin

Question 30

Extensor carpi radialis longus ## Footnote

Answer 30

**Origin:** Lateral supracondylar ridge of humerus **Insertion:** Base of metacarpal II **Action:** Extends wrist; aids in radial flexion of wrist

Question 31

Extensor carpi radialis brevis ## Footnote

Answer 31

**Origin:** Lateral epicondyle of humerus **Insertion:** Base of metacarpal III **Action:** Extends wrist; aids in radial flexion of wrist

Question 32

Extensor carpi ulnaris ## Footnote

Answer 32

**Origin:** Lateral epicondyle of humerus; posterior surface of ulnar shaft **Insertion:** Base of metacarpal V **Action:** Extends and fixes wrist when fist is clenched or hand grips an object; aids in ulnar flexion of wrist

Question 33

Extensor digitorum

Answer 33

**Origin:** Lateral epicondyle of humerus **Insertion:** Dorsal surfaces of phalanges II-V **Action:** Extends wrist, metacarpophalangeal, and interphalangeal joints; tends to spread digits apart when extending metacarpophalangeal joints

Question 34

Rectus abdominis

Answer 34

**Origin:** Pubic symphysis and superior margin of pubis **Insertion:** Xiphoid process, costal cartilages 5-7 **Action:** Flexes lumbar region of vertebral column, producing forward bending at the waist

Question 35

Erector Spinae

Answer 35

**Origin:** Nuchal ligament, ribs 3-12, thoracic and lumbar vertebrae, median and lateral sacral crests, thoracolumbar fascia **Insertion:** Mastoid process, cervical and thoracic vertebrae, and all ribs **Action:** Extension and lateral flexion of vertebral column;

Question 36

Semispinalis thoracis

Answer 36

**Origin:** Vertebrae T6-T10 **Insertion:** Vertebrae C6-T4 **Action:** Extension and contralateral rotation of vertebral column

Question 37

Multifidus

Answer 37

**Origin:** Vertebrae C4-L5, posterior superior iliac spine, sacrum, aponeurosis of erector spinae **Insertion:** Laminae and spinous processes of vertebrae superior to origins **Action:** Stabilization of adjacent vertebrae, maintenance of posture, control of vertebral movement when erector spinae acts on vertebral column

Question 38

Quadratus lumborum

Answer 38

**Origin:** Iliac crest, iliolumbar ligament **Insertion:** Rib 12 and vertebrae L1-L4 **Action:** Aids respiration by fixing rib 12 and stabilizing inferior attachments of diaphragm. * _Unilateral contraction_ causes ipsilateral flexion of lumbar vertebral column; * _bilateral contraction_ extends lumbar vertebral column.

Question 39

External oblique

Answer 39

**Origin:** Ribs 5-12 **Insertion:** Anterior half of iliac crest, pubic symphysis, and superior margin of pubis **Action:** Supports abdominal viscera against pull of gravity; stabilizes vertebral column; maintains posture; compresses abdominal organs; unilateral contraction causes contralateral rotation of waist

Question 40

Internal oblique

Answer 40

**Origin:** Inguinal ligament, iliac crest, and thoracolumbar fascia **Insertion:** Ribs 10-12, costal cartilages 7-10, pubis **Action:** Supports abdominal viscera against pull of gravity; stabilizes vertebral column; maintains posture; compresses abdominal organs; unilateral contraction causes ipsilateral rotation of waist

Question 41

Transverse abdominis

Answer 41

**Origin:** Inguinal ligament, iliac crest, thoracolumbar fascia, costal cartilages 7-12 **Insertion:** Linea alba, pubis, aponeurosis of internal oblique **Action:** Compresses abdominal contents

Question 42

External intercostals

Answer 42

**Origin:** Inferior margins of ribs 1-11 **Insertion:** Superior margin of next lower rib **Action:** When scalenes fix rib 1, external intercostals elevate and protract ribs 2-12, expanding the thoracic cavity and creating a partial vacuum causing inflow of air; exercise a braking action during expiration so that expiration is not overly abrupt

Question 43

Internal intercostals

Answer 43

**Origin:** Superior margins and costal cartilages of ribs 2-12; margin of sternum **Insertion:** Inferior margin of next higher rib **Action:** Elevates and depresses ribs to aid in inspriation and expiration