9.6: Appendicular Muscles of the Pectoral Girdle and Upper Limbs
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- 63431
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Identify the muscles of the pectoral girdle and upper limbs
- Identify the movement and function of the pectoral girdle and upper limbs
Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers. The pectoral girdle, or shoulder girdle, consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.
Muscles That Move the Pectoral Girdle at the Sternoclavicular Joint
Muscles that position the pectoral girdle are located either on the anterior thorax or on the posterior thorax (Figure \(\PageIndex{1}\) and Table \(\PageIndex{1}\)). The anterior muscles include the subclavius, pectoralis minor, and serratus anterior. The posterior muscles include the trapezius, levator scapulae, rhomboid major, and rhomboid minor. When the rhomboids are contracted, your scapula moves medially, which can pull the shoulder and upper limb posteriorly.
Table \(\PageIndex{1}\): Muscles that Position the Pectoral Girdle
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Levator scapulae | Transverse processes of C1-C4 | Superior, medial border of scapula | Elevates and inferiorly rotates scapula (video) |  |
| Pectoralis minor | Anterior surfaces of certain ribs (2 - 4 or 3 - 5) | Coracoid process of scapula | Rotates shoulder anteriorly (throwing motion); assists with inhalation |  |
| Rhomboid major | Thoracic vertebrae (T2 - T5) | Medial border of scapula | Retracts scapula (video) |  |
| Rhomboid minor | Cervical and thoracic vertebrae (C7 and T1) | Medial border of scapula | Retracts scapula (video) |  |
| Serratus anterior | Muscle slips from certain ribs (1 - 8 or 1 - 9) | Anterior surface of vertebral border of scapula | Protracts scapula (video) |  |
| Trapezius | Skull; vertebral column | Acromion and spine of scapula; clavicle |
Dependent upon which fibers are stimulated (video):
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Muscles That Move the Humerus at the Shoulder Joint
Similar to the muscles that position the pectoral girdle, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles (Figure \(\PageIndex{2}\) and Table \(\PageIndex{2}\)). The two muscles that originate on the axial skeleton are the pectoralis major and the latissimus dorsi. The pectoralis major is thick and fan-shaped, covering much of the superior portion of the anterior thorax. The broad, triangular latissimus dorsi is located on the inferior part of the back, where it inserts into a thick connective tissue sheath called an aponeurosis.
Table \(\PageIndex{2}\): Muscles that Move the Humerus at the Shoulder Joint
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Latissimus dorsi | Thoracic vertebrae (T7-T12); lumbar vertebrae; lower ribs (9-12); iliac crest | Intertubercular sulcus of humerus | Extends, adducts, and internally rotates shoulder (video) |  |
| Pectoralis major | Clavicle; sternum; cartilage of certain ribs (1-6 or 1-7); aponeurosis of external oblique muscle | Greater tubercle of humerus | Flex, adduct, and internally rotate shoulder (video) |  |
| Coracobrachialis | Coracoid process of scapula | Medial surface of humerus shaft | Flex and adduct shoulder |  |
| Deltoid | Trapezius; clavicle; acromion and spine of scapula | Deltoid tuberosity of humerus |
Extends, abducts, and flexes shoulder (video) - motion is dependent upon which fibers are activated |
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| Subscapularis (part of rotator cuff) | Subscapular fossa of scapula | Lesser tubercle of humerus | Adduct and internally rotate shoulder; stabilizes shoulder joint during movement of the pectoral girdle (video) |  |
| Infraspinatus (part of rotator cuff) | Infraspinous fossa of scapula | Greater tubercle of humerus | Externally rotate shoulder (video) |  |
| Supraspinatus (part of rotator cuff) | Supraspinous fossa of scapula | Greater tubercle of humerus | Abduct shoulder (video) |  |
| Teres major | Posterior surface of scapula | Intertubercular sulcus of humerus | Adduct and internally rotate shoulder |  |
| Teres minor (part of rotator cuff) | Lateral border of dorsal scapular surface | Greater tubercle of humerus | Externally rotate shoulder |  |
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The rest of the shoulder muscles originate on the scapula. The anatomical and ligamental structure of the shoulder joint and the arrangements of the muscles covering it, allows the arm to carry out different types of movements. The deltoid, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation. The subscapularis originates on the anterior scapula and medially rotates the arm. Named for their locations, the supraspinatus (superior to the spine of the scapula) and the infraspinatus (inferior to the spine of the scapula) abduct the arm, and laterally rotate the arm, respectively. The thick and flat teres major is inferior to the teres minor and extends the arm, and assists in adduction and medial rotation of it. The long teres minor laterally rotates and extends the arm. Finally, the coracobrachialis flexes and adducts the arm.
The tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bring the arm overhead to throw a fast pitch.
Muscles That Move the Forearm at the Elbow Joint
The forearm, containing the radius and ulna, has two actions at the hinge of the elbow joint: flexion, extension. The the muscles that cause flexion at the elbow joint include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus.
The biceps brachii, brachialis, and brachioradialis flex the forearm at the elbow. The two-headed biceps brachii crosses the shoulder and elbow joints to flex the forearm, also taking part in supinating the forearm at the radioulnar joints and flexing the arm at the shoulder joint. Deep to the biceps brachii, the brachialis provides additional power in flexing the forearm. Finally, the brachioradialis can flex the forearm quickly or help lift a load slowly. These muscles and their associated blood vessels and nerves form the anterior compartment of the arm (anterior flexor compartment of the arm) (Figure \(\PageIndex{3}\) and Table \(\PageIndex{3}\)).
Table \(\PageIndex{3}\): Muscles that Move the Forearm at the Elbow Joint
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Anterior Muscles (Flexion) | ||||
| Biceps brachii | Coracoid process; tubercle above glenoid cavity | Radial tuberosity |
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| Brachialis | Front of distal humerus | Coronoid process of ulna | Elbow flexion |  |
| Brachioradialis | Lateral supracondylar ridge at distal end of humerus | Base of styloid process of radius | Assists in elbow flexion |  |
| Posterior Muscles (Extension) | ||||
| Anconeus | Lateral epicondyle of humerus | Lateral aspect of olecranon process of ulna | Assists in extending elbow joint |  |
| Triceps brachii | Infraglenoid tubercle of scapula; posterior shaft of humerus; posterior humeral shaft distal to the radial groove | Olecranon process of ulna | Extends elbow and shoulder |  |
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Muscles That Move the Forearm at the Radioulnar Joints
The pronators are the pronator teres and the pronator quadratus, and the supinator is the only one that turns the forearm anteriorly. When the forearm faces anteriorly, it is supinated. When the forearm faces posteriorly, it is pronated. (Table \(\PageIndex{4}\))
Table \(\PageIndex{4}\): Muscles that Move the Forearm at the Elbow Joint
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Anterior Muscles (Pronation) | ||||
| Pronator quadratus | Distal portion of anterior ulnar shaft | Distal surface of anterior radius | Assists in turning hand palm posterior (pronation of radioulnar joint) |  |
| Pronator teres | Medial epicondyle of humerus; coronoid process of ulna | Lateral radius | Turns hand palm posterior (pronation of radioulnar joint) |  |
| Posterior Muscles (Supination) | ||||
| Supinator | Lateral epicondyle of humerus; proximal ulna | Proximal end of radius | Turns hand palm anterior (supinator of radioulnar joint) |  |
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Muscles That Move the Wrist, Hand, and Fingers
Wrist, hand, and finger movements are facilitated by two groups of muscles. The forearm is the origin of the extrinsic muscles of the hand. The palm is the origin of the intrinsic muscles of the hand.
Muscles of the Forearm That Move the Wrists, Hands, and Fingers
The muscles in the anterior compartment of the forearm (anterior flexor compartment of the forearm) originate on the humerus and insert onto different parts of the hand. These make up the bulk of the forearm. From lateral to medial, the superficial anterior compartment of the forearm includes the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. The flexor digitorum superficialis flexes the hand as well as the digits at the knuckles, which allows for rapid finger movements, as in typing or playing a musical instrument (Figure \(\PageIndex{4}\) and Table \(\PageIndex{5}\)). However, poor ergonomics can irritate the tendons of these muscles as they slide back and forth with the carpal tunnel of the anterior wrist and pinch the median nerve, which also travels through the tunnel, causing Carpal Tunnel Syndrome. The deep anterior compartment produces flexion and bends fingers to make a fist. These are the flexor pollicis longus and the flexor digitorum profundus.
The muscles in the superficial posterior compartment of the forearm (superficial posterior extensor compartment of the forearm) originate on the humerus. These are the extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris.
The muscles of the deep posterior compartment of the forearm (deep posterior extensor compartment of the forearm) originate on the radius and ulna. These include the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis (Figure \(\PageIndex{5}\), Table \(\PageIndex{5}\)).
| Prime Mover | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Superficial/Intermediate Anterior Compartment of Forearm | ||||
| Flexor carpi ulnaris | Medial epicondyle of humerus; olecranon process; posterior surface of ulna | Pisiform bone; hamate bone; base of fifth metacarpal | Assists in bending hand up toward shoulder; tilts hand to side away from body; stabilizes wrist |  |
| Flexor carpi radialis | Medial epicondyle of humerus | Base of second and third metacarpals | Bends wrist toward body; tilts hand to side away from body |  |
| Flexor digitorum superficialis | Medial epicondyle of humerus; coronoid process of ulna; shaft of radius | Middle phalanges of fingers 2 - 5 | Bends fingers to make fist |  |
| Palmaris longus | Medical epicondyle of humerus | Palmar aponeurosis; skin and fascia of palm | Assists in bending hand up toward shoulder |  |
| Deep Anterior Compartment of Forearm | ||||
| Flexor digitorum profundus | Coronoid process; anteromedial surface of ulna; interosseous membrane | Distal phalanges of fingers 2 - 5 | Bends fingers to make a fist; also bends wrist toward body |  |
| Flexor pollicus longus | Anterior surface of radius; interosseous membrane | Distal phalanx of thumb | Bends tip of thumb |  |
| Superficial Posterior Compartment of Forearm | ||||
| Extensor carpi radialis brevis | Lateral epicondyle of humerus | Base of third metacarpal | Assists extensor radialis longus in extending and abducting wrist; also stabilizes hand during finger flexion |  |
| Extensor carpi ulnaris | Lateral epicondyle of humerus; posterior border of ulna | Base of fifth metacarpal | Straightens wrist away from body; tilts hand to side toward body |  |
| Extensor digiti minimi | Lateral epicondyle of humerus | Extensor expansion; distal phalanx of finger 5 (little finger) | Extends finger 5 (little finger) |  |
| Extensor digitorum | Lateral epicondyle of humerus | Extensor expansions; distal phalanges of fingers | Opens fingers and moves them sideways away from the body |  |
| Extensor radialis longus | Lateral supracondylar ridge of humerus | Base of second metacarpal | Straightens wrist away from body |  |
| Deep Posterior Compartment of Forearm | ||||
| Abductor pollicis longus | Posterior surface of radius and ulna; interosseous membrane | Base of first metacarpal; trapezium | Moves thumb sideways toward body; extends thumb; moves hand sideways toward body |  |
| Extensor indicis | Posterior surface of distal ulna; interosseous membrane | Tendon of extensor digitorum of finger 2 (index finger) | Extends finger 2 (index finger); straightens wrist away from body |  |
| Extensor pollicis brevis | Dorsal shaft of radius and ulna; interosseous membrane | Base of proximal phalanx of thumb | Extends thumb |  |
| Extensor pollicis longus | Dorsal shaft of radius and ulna; interosseous membrane | Base of distal phalanx of thumb | Extends thumb |  |
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The tendons of the forearm muscles attach to the wrist and extend into the hand. Fibrous bands called retinacula sheath the tendons at the wrist. The flexor retinaculum extends over the palmar surface of the hand while the extensor retinaculum extends over the dorsal surface of the hand.
Intrinsic Muscles of the Hand
The intrinsic muscles of the hand both originate and insert within it (Figure \(\PageIndex{6}\), Table \(\PageIndex{6}\)). These muscles allow your fingers to also make precise movements for actions, such as typing or writing. These muscles are divided into three groups. The thenar muscles are on the radial aspect of the palm. The hypothenar muscles are on the medial aspect of the palm, and the intermediate muscles are midpalmar.
The thenar muscles include the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and the adductor pollicis. These muscles form the thenar eminence, the rounded contour of the base of the thumb, and all act on the thumb. The movements of the thumb play an integral role in most precise movements of the hand.
The hypothenar muscles include the abductor digiti minimi, flexor digiti minimi brevis, and the opponens digiti minimi. These muscles form the hypothenar eminence, the rounded contour of the little finger, and as such, they all act on the little finger. Finally, the intermediate muscles act on all the fingers and include the lumbrical, the palmar interossei, and the dorsal interossei.
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Thenar Muscles (movements video) | ||||
| Abductor pollicis brevis | Flexor retinaculum; and nearby carpals | Lateral base of proximal phalanx of thumb | Abducts and flexes thumb |   |
| Adductor pollicis | Capitate bone; bases of metacarpals 2 - 4; front of metacarpal 3 | Medial base of proximal phalanx of thumb | Adducts and flexes thumb |  |
| Flexor pollicis brevis | Flexor retinaculum; trapezium | Lateral base of proximal phalanx of thumb | Flexes thumb |   |
| Opponens pollicis | Flexor retinaculum; trapezium | Anterior of first metacarpal | Opposes thumb (moves thumb across palm to touch other fingers) |  |
| Hypothenar Muscles | ||||
| Abductor digiti minimi | Pisiform bone | Medial side of proximal phalanx of finger 5 (little finger) | Abducts and flexes MCP of 5th digit |   |
| Flexor digiti minimi brevis | Hamate bone; flexor retinaculum | Medial side of proximal phalanx of finger 5 (little finger) | Flexes MCP of 5th digit |  |
| Opponens digiti minimi | Hamate bone; flexor retinaculum | Medial side of fifth metacarpal | Opposes digit 5 (moves little finger across palm to touch thumb) |  |
| Deep Muscles | ||||
| Dorsal interossei | Sides of metacarpals | Both sides of finger 3; for each other finger, extensor expansion over first phalanx on side opposite finger 3 | Abducts and flexes the three middle fingers at metacarpo-phalangeal joints; extends the three middle fingers at interphalangeal joints |  |
| Lumbricals | Palm (lateral sides of tendons in flexor digitorum profundus) | Fingers 2–5 (lateral edges of extensional expansions on first phalanges) | Flexes each finger at metacarpo-phalangeal joints; extends each finger at interphalangeal joints |  |
| Palmar interossei | Side of each metacarpal that faces metacarpal 3 (absent from metacarpal 3) | Extensor expansion on first phalanx of each finger (except finger 3) on side facing finger 3 | Adducts and flexes each finger at metacarpo-phalangeal joints; extends each finger at interphalangeal joints |  |
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Explore the muscles of the upper limb in this 3D model of an arm model.
Concept Review
The clavicle and scapula make up the pectoral girdle, which provides a stable origin for the muscles that move the humerus. The muscles that position and stabilize the pectoral girdle are located on the thorax. The anterior thoracic muscles are the subclavius, pectoralis minor, and the serratus anterior. The posterior thoracic muscles are the trapezius, levator scapulae, rhomboid major, and rhomboid minor. Nine muscles cross the shoulder joint to move the humerus. The ones that originate on the axial skeleton are the pectoralis major and the latissimus dorsi. The deltoid, subscapularis, supraspinatus, infraspinatus, teres major, teres minor, and coracobrachialis originate on the scapula.
The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus. The pronators are the pronator teres and the pronator quadratus. The supinator is the only one that turns the forearm anteriorly.
The extrinsic muscles of the hands originate along the forearm and insert into the hand in order to facilitate crude movements of the wrists, hands, and fingers. The superficial anterior compartment of the forearm produces flexion. These muscles are the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor digitorum superficialis. The deep anterior compartment produces flexion as well. These are the flexor pollicis longus and the flexor digitorum profundus. The rest of the compartments produce extension. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris are the muscles found in the superficial posterior compartment. The deep posterior compartment includes the abductor longus, extensor pollicis brevis, extensor pollicis longus, and the extensor indicis.
Finally, the intrinsic muscles of the hands allow our fingers to make precise movements, such as typing and writing. They both originate and insert within the hand. The thenar muscles, which are located on the lateral part of the palm, are the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and adductor pollicis. The hypothenar muscles, which are located on the medial part of the palm, are the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi. The intermediate muscles, located in the middle of the palm, are the lumbricals, palmar interossei, and dorsal interossei.
Review Questions
Query \(\PageIndex{1}\)
Critical Thinking Questions
Query \(\PageIndex{2}\)
Query \(\PageIndex{3}\)
Glossary
Query \(\PageIndex{4}\)
Contributors and Attributions
OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology