chapter 12 muscular system iii anatomy and physiology

Pectoralis Minor

• protraction of shoulder, as in reaching out for a door handle

• rotation of scapula and depression of apex of shoulder, as in reaching down to pick up a suitcase

Serratus Anterior

• rotation of scapula as in lifting a suitcase or raising arm above head

• fixation of scapula when carrying weights in front of body; protraction of scapula

• prime mover of all forward-reaching and pushing actions

• nicknamed the 'boxer's muscle' for its role in powerful thrusting movements such as a boxer's jab

Trapezius

• lateral rotation of scapula, elevating apex of shoulder as in picking up a suitcase

• elevation of scapula as in shrugging shoulders

• retraction of scapula as in pulling on a rope

• fast, forcible depression of scapula as in hammering and swimming

• fixation of scapula and shoulder during other arm movements

Levator Scapulae

• elevation of scapula

• medial rotation of scapula, depressing apex of shoulder

• retraction of scapula and bracing of shoulder

• lateral flexion of neck

Rhomboid Minor

• retraction of scapula and bracing of shoulder

• fixation of scapula during other arm movements

Rhomboid Major

Same as rhomboid minor

Pectoral Girdle

In humans, it consists of the clavicle (collarbone) and the scapula (shoulder blade)

Pelvic Girdle

consists of two hip bones (also called coxal bones or os coxae) that fuse with the sacrum and coccyx to form the pelvis

Rotator cuff

A fibrous sleeve formed by tendons from four scapular muscles that merge with the joint capsule of the shoulder

Supraspinatus

A rotator cuff muscle that originates from the supraspinous fossa of the scapula and is responsible for abduction of the arm

Infraspinatus

A rotator cuff muscle that originates from the infraspinous fossa of the scapula and is responsible for lateral rotation of the arm

Teres Minor

A rotator cuff muscle that is responsible for adduction and lateral rotation of the arm

Subscapularis

A rotator cuff muscle that originates from the subscapular fossa of the scapula and is responsible for medial rotation of the arm

Deltoid

A superficial, triangular muscle that caps the shoulder and has anterior, lateral, and posterior fibers that move the arm in different directions

Teres Major

A scapular muscle that assists in medial rotation and shoulder extension

Coracobrachialis

A scapular muscle that aids in medial rotation of the humerus and shoulder flexion

Latissimus Dorsi

A broad muscle of the back extending from the waist to the humerus, responsible for medial rotation and adduction of the arm

Pectoralis Major

A large, superficial muscle extending from the thorax to the humerus, responsible for medial rotation and adduction of the arm

Abduction of arm

The action of moving the arm away from the body

Lateral rotation of arm

The action of rotating the arm outward away from the body

Medial rotation of arm

The action of rotating the arm inward towards the body

Shoulder flexion

The action of raising the arm forward

Shoulder extension

The action of moving the arm backward.

Arm swinging

The motion of moving the arm back and forth, as in walking or bowling.

Resists downward slippage

The function of certain muscles to prevent the humeral head from sliding down when the arm is relaxed or carrying weight

Resists upward slippage

The function of certain muscles to prevent the humeral head from sliding up when the arm is abducted

Innervation

The supply of nerves to a specific muscle or body part

Suprascapular nerve

The nerve that innervates the supraspinatus and infraspinatus muscles

Axillary nerve

The nerve that innervates the deltoid and teres minor muscles

Upper and lower subscapular nerves

The nerves that innervate the subscapularis muscle.

Medial and lateral pectoral nerves

The nerves that innervate the pectoralis major muscle.

Thoracodorsal nerve

The nerve that innervates the latissimus dorsi muscle.

Vastus lateralis

A muscle commonly used for IM injections.

Gluteus maximus

A muscle commonly used for IM injections.

Gluteus medius

A muscle commonly used for IM injections.

Brachialis

Prime mover of elbow flexion.

Biceps Brachii

• synergist in elbow flexion and is also a powerful supinator

• has a long head and short head.

Triceps Brachii

Prime mover of elbow extension; has three muscle heads (long, medial, and lateral).

Brachioradialis

• extends from distal humerus to distal radius

• functions in elbow flexion, pronation, and supination

Pronator Teres

Functions in forearm pronation.

Pronator Quadratus

Functions in forearm pronation; resists separation of radius and ulna when force is applied to forearm.

Supinator

Functions in forearm supination, as in turning a doorknob or driving a screw into wood.

Musculocutaneous nerve

Innervates the Brachialis and Biceps Brachii.

Radial nerve

Innervates the Triceps Brachii, Brachioradialis, and Supinator.

Median nerve

Innervates the Pronator Quadratus and Pronator Teres.

Elbow flexion

Action performed by Brachialis and Biceps Brachii.

Elbow extension

Action performed by triceps brachii

Forearm pronation

Action performed by Pronator Teres and Pronator Quadratus.

Forearm supination

Action performed by Supinator.

Long head

Part of Biceps Brachii that stabilizes shoulder by holding humeral head against glenoid cavity

Short head

Part of Biceps Brachii originating from coracoid process

Olecranon

Insertion point for Triceps Brachii

Fascia of forearm

Insertion point for Triceps Brachii and Brachioradialis.

Coronoid process

Attachment point for Biceps Brachii

Extrinsic muscles

Muscles in the forearm that act on metacarpophalangeal joints or interphalangeal joints of the hand.

Flexor retinaculum

A ligament under which anterior tendons pass through the carpal tunnel

Extensor retinaculum

A ligament under which posterior tendons pass.

Anterior compartment

Contains superficial and deep layers of muscles that mostly arise from a common tendon on the medial epicondyle of the humerus and primarily flex the wrist or fingers

Posterior compartment

Contains superficial and deep layers of muscles that mostly arise from a common tendon on the lateral epicondyle of the humerus and primarily extend the wrist or fingers

Flexor Carpi Radialis

• muscle responsible for anterior and radial flexion of the wrist

• arises from the medial epicondyle of the humerus

Flexor Carpi Ulnaris

• muscle responsible for anterior and ulnar flexion of the wrist

• arises from the medial epicondyle of the humerus, medial margin of olecranon, and posterior surface of ulna

Flexor Digitorum Superficialis

• muscle that flexes the wrist, metacarpophalangeal, and interphalangeal joints

• arises from the medial epicondyle of the humerus and other structures

Palmaris Longus

• muscle that assists in wrist flexion and provides anchorage for palmar skin and fascia

• arises from the medial epicondyle of the humerus

Flexor Digitorum Profundus

• sole flexor of distal interphalangeal joints

• arises from the proximal 3/4 of ulna and other structures

Flexor Pollicis Longus

Muscle responsible for thumb flexion; arises from the radius and interosseous membrane.

Extensor Carpi Radialis Longus

• muscle that extends and radially flexes the wrist

• arises from the lateral supracondylar ridge of the humerus

Extensor Carpi Radialis Brevis

• muscle that extends and radially flexes the wrist

• arises from the lateral epicondyle of the humerus

Extensor Digitorum

Muscle that extends the wrist, metacarpophalangeal, and interphalangeal joints; tends to spread fingers away from each other.

Extensor Digiti Minimi

• muscle that extends the wrist and little finger

• arises from the lateral epicondyle of the humerus

Extensor Carpi Ulnaris

• muscle that extends and ulnarly flexes the wrist

• provides wrist fixation when the fist is clenched

Abductor Pollicis Longus

• muscle responsible for radial abduction of the thumb and extension of the carpometacarpal joint of the thumb

Extensor Pollicis Brevis

Muscle that extends the thumb at carpometacarpal and metacarpophalangeal joints.

Proximal phalanx I

The first bone in the finger located between the metacarpal and the distal phalanx.

Extensor Pollicis Longus

• extension of thumb at carpometacarpal and metacarpophalangeal joints of thumb

• adduction and lateral rotation of thumb

Distal phalanx I

The last bone in the thumb, located at the tip.

Extensor Indicis (IN-dih-sis)

Extension of index finger at metacarpophalangeal and interphalangeal joints.

Intrinsic Muscles of the Hand

Muscles contained entirely within hands, assist extrinsic muscles in forearm.

Thenar group

Muscles that move the thumb; they abduct, adduct, flex, and oppose the thumb.

Hypothenar group

Muscles that move the little finger; they abduct, flex, and oppose the little finger

Midpalmar group

Muscles in the hollow of the palm that act on fingers to provide a variety of movements.

Adductor Pollicis

Thumb adduction as in gripping a tool.

Abductor Pollicis Brevis

Thumb abduction.

Flexor Pollicis Brevis

Thumb flexion at metacarpophalangeal joint.

Opponens Pollicis

Flexion of metacarpophalangeal joint I, producing opposition of thumb to fingertips.

Abductor Digiti Minimi

Abduction of little finger, as in spreading fingers apart.

Flexor Digiti Minimi Brevis

Flexion of little finger at metacarpophalangeal joint.

Opponens Digiti Minimi

Flexion of carpometacarpal joint V, as in moving little finger into opposition with thumb.

Dorsal Interosseous Muscles (IN-tur-OSS-ee-us)

• finger abduction

• strong flexion of metacarpophalangeal joints or extension of interphalangeal joints, depending on action of other muscles

Palmar Interosseous Muscles

Finger adduction; other actions same as for dorsal interosseous muscles.

Lumbrical Muscles (LUM-brih-cul)

Interphalangeal joint extension, enabling one to pinch objects between fleshy pads of thumb and other fingertips.

Metacarpals I, II, IV, V

Bones in the hand that support the palm.

Proximal phalanges II, IV, V

The first segment of the fingers corresponding to the second, fourth, and fifth digits.

Tendons of flexor digitorum profundus

Tendons that flex the distal joints of the fingers.

Four Lumbrical Muscles

Muscles in the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.

Ulnar nerve

A nerve that runs along the inner side of the arm and hand, responsible for sensation and muscle control.

Interphalangeal joint extension

Movement that allows one to pinch objects between fleshy pads of the thumb and other fingertips.

Iliacus

A muscle that flexes the hip when the trunk is fixed and assists in waist flexion when the thigh is fixed.

Psoas major

A muscle that acts as an antagonist to biceps femoris and is involved in hip flexion.

Iliopsoas

A collective term for the iliacus and psoas major muscles.

Fascia lata

A fibrous sheath encircling the thigh.