Pictorial Guide to Muscles and Surface Anatomy

Henry L. Lew

Su-Ju Tsai

Table 8-1 Masseter (Fig. 8-1)

Figure 8-1 • Masseter muscle	Innervation	Mandibular division of the trigeminal nerve (cranial nerve V), mesencephalon
	Origin	Lower and medial aspect of the zygomatic arch
	Insertion	Lateral aspect of the mandibular ramus
	Action	Elevation of the mandible for mastication
	Position	Supine with the head turned to the other side or lateral decubitus
	Activation	Teeth clenching
	Needle placement	This muscle is midway between the angle of the jaw and the temporomandibular joint.
	Notes	Needle is held at oblique angle of 20 degrees from the skin. Muscles are too thin for perpendicular insertion. Motor unit potentials are smaller in both amplitude and duration than those seen in limb muscles.

Table 8-2 Temporalis (Fig. 8-2)

Figure 8-2 • Temporalis	Innervation	Deep temporal nerve—mandibular division of the trigeminal nerve (cranial nerve V), mesencephalon
	Origin	Bony floor of the temporal fossa and the deep surface of the temporal fascia
	Insertion	Coronoid process and anterior border of the ramus of the mandible
	Action	Elevation and retraction of the mandible
	Position	Supine with the head turned to the other side or lateral decubitus
	Activation	Teeth clenching
	Needle placement	Vertically above its insertion at the mandible, insert 1–2 cm below the skull ridge from which it arises. Palpate temporal artery to avoid.
	Notes	See notes in Table 8-1.

Table 8-3 Auricularis Posterior (Fig. 8-3)

Figure 8-3 • Auricularis posterior	Innervation	Facial nerve (cranial nerve VII), pons
	Origin	Mastoid process
	Insertion	Cartilage of the ear
	Action	Retraction of the earlobe
	Position	Supine with the head turned to the other side or lateral decubitus
	Needle placemen	Posterior to the midpoint of the ear; can be absent and some patients cannot activate voluntarily
	Notes	See notes in Table 8-1.

Table 8-4 Frontalis (Fig. 8-4)

Figure 8-4 • Frontalis	Innervation	Temporal branch of the facial nerve (cranial nerve VII), pons
	Origin	Frontal skin and superficial fascia of the eyebrow
	Insertion	Epicranial aponeurosis
	Action	Raise the eyebrows
	Position	Supine
	Activation	Raise the eyebrows or look upward.
	Needle placement	The frontalis muscle is 5 cm above the eyebrow, superior to most of the wrinkles on the forehead that it makes.
	Notes	See notes in Table 8-1.

Table 8-5 Orbicularis Oculi (Fig. 8-5)

Figure 8-5 • Orbicularis oculi	Innervation	Temporal and zygomatic branches of the facial nerve (cranial nerve VII), pons
	Origin	Medial palpebral ligament and adjacent bones
	Insertion	Lateral palpebral raphe and adjacent tissues
	Action	Closure of the eyelids and dilatation of the lacrimal sac
	Position	Supine
	Activation	Close eyes, resist opening.
	Needle placement	Palpate the margin of the orbital fossa, and insert the needle in 20° lateral to the margin. Direct the needle to avoid the eyeball.
	Notes	See notes in Table 8-1.

Table 8-6 Nasalis (Fig. 8-6)

Figure 8-6 • Nasalis	Innervation	Buccal branch of the facial nerve (cranial nerve VII), pons
	Origin	Maxilla
	Insertion	Ala of the nose
	Action	Widening of the nasal aperture
	Position	Supine
	Activation	Deep inspiration through the nostril
	Needle placement	Study this muscle just below the bone–cartilage junction of the nose.
	Notes	See notes in Table 8-1.

Table 8-7 Mentalis (Fig. 8-7)

Figure 8-7 • Mentalis	Innervation	Mandibular branch of the facial nerve (cranial nerve VII), pons
	Origin	Mandible
	Insertion	Skin on the chin
	Action	Protrusion of the lower lip
	Position	Supine
	Activation	Protrude the lower lip; “pucker.”
	Needle placement	Just above the corners of the anterior jaw
	Notes	See notes in Table 8-1.

Table 8-8 Orbicularis Oris (Fig. 8-8)

Figure 8-8 • Orbicularis oris	Innervation	Buccal and mandibular branches of the facial nerve (cranial nerve VII), pons
	Origin	Encircling fibers from the deep surface of the skin, the buccinator
	Insertion	Skin and mucous membrane lining the inner surface of the lips
	Action	Compressing the lips together
	Position	Supine
	Activation	Lip pucker
	Needle placement	This is the deepest-lying of the facial muscles; insert just lateral to mouth angle, with 30° angle for deeper penetration.
	Note	See notes in Table 8-1.

Table 8-9 Sternocleidomastoid (Fig. 8-9)

Figure 8-9 • Sternocleidomastoid	Innervation	Spinal accessory nerve (cranial nerve XI) and the anterior rami of the C2 and C3 nerves, medulla
	Origin	Upper portion of the sternum and the medial third of the upper surface of the clavicle
	Insertion	Mastoid process and lateral portion of the superior nuchal line of the occipital bone
	Action	Tilting of the head to the same side, and turning the chin to the opposite side
	Position	Supine
	Activation	Rotate the head to opposite side.
	Needle placement	Midway between the mastoid and the clavicle; pinch muscle and lift to avoid penetrating too deeply.

Table 8-10 Trapezius (Fig. 8-10)

Figure 8-10 • Trapezius	Innervation	Spinal accessory nerve (cranial nerve XI), C3 and C4 cervical nerves, medulla
	Origin	External occipital protuberance, ligamentum nuchae, and spinous processes of the C7 and T1–T12 vertebrae
	Insertion	Lateral third of the clavicle, the acromion, and the spine of the scapula
	Action	Adduction and rotation (elevating the acromion) of the scapula
	Position	Prone, lateral decubitus, or sitting
	Activation	Shrug shoulders.
	Needle placement	Draw a line from the C7 spinous process to the acromion and insert in the center of this line.

Table 8-11 Tongue (Fig. 8-11)

Figure 8-11 • Tongue	Innervation	Hypoglossal nerve (cranial nerve XII), medulla
	Origin	Superior genial spine of the mandible
	Insertion	Inferior portion of the tongue blending with other tongue muscles
	Action	Protrusion and lateral movement of apex of the tongue
	Position	Supine with the head turned to the other side
	Activation	Tongue protrusion or contralateral movement
	Needle placement	Insert vertically upward 1 cm posterior to the (posterior) edge of the mental portion of the mandible and 1 cm from center.

Table 8-12 Diaphragm (Fig. 8-12)

Figure 8-12 • Diaphragm	Innervation	Phrenic nerve: C3, C4, C5
	Origin	Lower six ribs, internal surface of xiphoid process, medial and lateral arcuate ligaments from transverse processes of L1 and L2 vertebrae
	Insertion	Central tendon of the diaphragm
	Action	Inspiration (depression of the diaphragm)
	Position	Supine
	Activation	Rapid inspiration with pursed lips for resistance
	Needle placement	From the costal margin, palpate the intercostal space below the 9th rib. Insert the needle perpendicular to the skin 1 cm lateral to the anterior articulation and close to the superior edge of the 10th rib. Keep amplifier on and observe the intercostal muscle EMG activity and the respiratory pattern. Penetrate deeper with the needle reaching the diaphragm, which is active only on inspiration. Note: For COPD patients with a depressed diaphragm at rest, insert the needle below the costal margin in the angle between the xiphoid process and the rib.

Table 8-13 Levator Scapulae (Fig. 8-13)

Figure 8-13 • Levator scapulae	Innervation	Dorsal scapular nerve, branches from C3 and C4
	Origin	Transverse processes of atlas, axis, C3, and C4
	Insertion	Medial border of the scapula, superior to the root of the spine
	Action	Elevation of the scapula
	Position	Prone, lateral decubitus, or sitting
	Activation	Shrug shoulder.
	Needle placement	Insert into the muscle above the medial-superior aspect of the scapula and activate with elevation of the shoulder.
	Note	When activating muscles for motor unit evaluation, use isometric contraction.

Table 8-14 Rhomboid Major (Fig. 8-14)

Figure 8-14 • Rhomboid major	Innervation	Dorsal scapular nerve—C5
	Origin	Spinous processes of the T2–T5 vertebrae
	Insertion	Medial border of the scapula, inferior to the spine
	Action	Adduction, retraction, and rotation of the scapula (acromion down)
	Position	Prone, lateral decubitus, or sitting
	Activation	Retraction (adduction) of the scapula
	Needle placement	Just medial to the inferior third of the scapula; this is a “keep-amplifier-on” muscle studied with retraction of the scapula.
	Note	“Keep-amplifier-on” refers to switching on the preamplifier with the needle tip in the dermis or subcutaneous layers. The tip is slowly advanced until the needle enters the muscle. This avoids accidental penetration through the intercostal space.

Table 8-15 Rhomboid Minor (Fig. 8-15)

Figure 8-15 • Rhomboid minor	Innervation	Dorsal scapular nerve—C5
	Origin	Spinous processes of the C7 vertebra and the T1 vertebra
	Insertion	Medial border of the scapula at the base of the spine of the scapula
	Action	Adduction, retraction, and elevation of the scapula
	Position	Prone, lateral decubitus, or sitting
	Activation	Retraction of the scapula
	Needle placement	Immediately medial to the scapular spine, this is studied with retraction-elevation of the scapula as a “keep-amplifier-on” muscle.
	Note	See notes in Table 8-14.

Table 8-16 Serratus Anterior (Fig. 8-16)

Figure 8-16 • Serratus anterior	Innervation	Long thoracic nerve—C5, C6, C7
	Origin	Anterior and upper surfaces of the upper eight to nine ribs
	Insertion	Anterior surface of the medial border of the scapula
	Action	Abduction and protraction of the scapula
	Position	Lateral decubitus or supine
	Activation	Forward flexion or protraction of shoulder
	Needle placement	Palpating ribs 6 and 7 in the mid-axillary line will show this muscle, which protracts the scapula. Place fingers in the intercostal spaces while you insert the needle toward the rib between the fingers.

Table 8-17 Supraspinatus (Fig. 8-17)

Figure 8-17 • Supraspinatus	Innervation	Suprascapular nerve—upper trunk—C5, C6
	Origin	Supraspinous fossa of the scapula
	Insertion	Greater tubercle of the humerus
	Action	Abduction and external rotation of the shoulder
	Position	Prone, lateral decubitus, or sitting
	Activation	Abduction or external rotation of the shoulder
	Needle placement	Just above the spine of the scapula and 2 cm from its medial border. Avoid the narrow lateral half of the scapula, which overlies apical lung tissue. By inserting the needle down to the bone, one is assured of passing through the trapezius completely.

Table 8-18 Infraspinatus (Fig. 8-18)

Figure 8-18 • Infraspinatus	Innervation	Suprascapular nerve—upper trunk—C5, C6
	Origin	Infraspinous fossa of scapula
	Insertion	Greater tubercle of the humerus
	Action	External rotation of the shoulder
	Position	Prone, lateral decubitus, or sitting
	Activation	Externally rotate the shoulder.
	Needle placement	Halfway between the inferior angle of the scapula and its spine, insert the needle 3 cm from the medial edge of the bone.

Table 8-19 Teres Major (Fig. 8-19)

Figure 8-19 • Teres major	Innervation	Lower subscapular nerve—posterior cord—posterior division—upper trunk—C5, C6
	Origin	Lower third lateral border of the scapula
	Insertion	Medial lip of bicipital groove of the humerus
	Action	Adduction, extension, and internal rotation of the arm
	Position	Prone, lateral decubitus, or sitting
	Activation	Internally rotate the shoulder.
	Needle placement	Along the lateral scapula, 2–3 cm above the inferior angle. This is a “keep-amplifier-on” muscle so that you do not pass through it.
	Note	See notes in Table 8-14.

Table 8-20 Pectoralis Major—Clavicular Head (Fig. 8-20)

Figure 8-20 • Pectoralis major—clavicular head	Innervation	Lateral pectoral nerve—lateral cord—anterior division—upper trunk—C5, C6
	Origin	Sternal half of the clavicle
	Insertion	Lateral lip of the bicipital groove of the humerus
	Action	Adduction, flexion, and internal rotation of the shoulder
	Position	Supine or sitting
	Activation	Internally rotate the shoulder.
	Needle placement	Study can be done lateral with shoulder externally rotated to extend and expose the muscle. Insert medial to the neck of the humerus. Alternatively, insert just below the middle of the clavicle.

Table 8-21 Biceps Brachii (Fig. 8-21)

Figure 8-21 • Biceps brachii	Innervation	Musculocutaneous nerve—lateral cord—anterior division—upper trunk—C5, C6
	Origin	Long head: supraglenoid tuberosity of the scapula Short head: tip of coracoid process of the scapula
	Insertion	Bicipital tuberosity of the radius
	Action	Supination of the forearm and elbow flexion
	Position	Supination of the forearm (elbow flexion preferentially activates brachialis)
	Activation	Supination of the forearm
	Needle placement	Insert into middle of superficial muscle belly. Fully supinate the forearm to bring this muscle anterior.

Table 8-22 Brachialis (Fig. 8-22)

Figure 8-22 • Brachialis	Innervation	Musculocutaneous nerve—lateral cord—anterior division—upper trunk—C5, C6
	Origin	Lower two thirds of anterior surface of the humerus
	Insertion	Anterior aspect of coronoid process and tuberosity of the ulna
	Action	Flexion of the elbow
	Position	Pronation and extension of the forearm, supine
	Activation	Flex the elbow.
	Needle placement	This is the primary muscle for elbow flexion. Approach from lateral at the distal third of the arm.

Table 8-23 Coracobrachialis (Fig. 8-23)

Figure 8-23 • Coracobrachialis	Innervation	Musculocutaneous nerve—lateral cord—anterior division—upper and middle trunk—C6, C7
	Origin	Tip of the coracoid process of the scapula
	Insertion	Middle of medial border of the humerus
	Action	Flexion and adduction of the shoulder
	Position	Arm at side, supine
	Activation	Flex the shoulder.
	Needle placement	Insert into the anterior axillary fold. Follow muscle line out from the inferior edge of the coracoid to midhumerus.

Table 8-24 Latissimus Dorsi (Fig. 8-24)

Figure 8-24 • Latissimus dorsi	Innervation	Thoracodorsal nerve—posterior cord—posterior division—upper, middle, and lower trunk—C6, C7, C8
	Origin	Spinous processes of lower six thoracic vertebrae, all lumber and sacral vertebrae, and posterior iliac crest
	Insertion	Floor of the bicipital groove of the humerus
	Action	Adduction, extension, and medial rotation of the shoulder
	Position	Prone or lateral decubitus, full shoulder flexion
	Activation	Resist shoulder extension.
	Needle placement	The posterior axillary fold contains this larger muscle. An anterior approach helps to avoid the lower trapezius.

Table 8-25 Deltoid (Fig. 8-25)

Figure 8-25 • Deltoid	Innervation	Axillary nerve (posterior and anterior branches)—posterior cord—posterior division—upper trunk—C5, C6
	Origin	Lateral third of the clavicle, upper aspect of acromion, and spine of the scapula
	Insertion	Deltoid tuberosity of the humerus
	Action	Abduction of the shoulder (assists with flexion and extension)
	Position	Anterior and middle heads: supine, lateral decubitus, or sitting Posterior head: prone, lateral decubitus, or sitting
	Activation	Abduct the shoulder (flexion, anterior; extension, posterior).
	Needle placement	For the anterior head, insert 1 cm lateral to the coracoid process. Insert midway between acromion and the tubercle for the middle head. The posterior head is below the posterior aspect of the glenoid.
	Note	Posterior branch—posterior head

Table 8-26 Teres Minor (Fig. 8-26)

Figure 8-26 • Teres minor	Innervation	Axillary nerve (posterior branch)—posterior cord—posterior division—upper trunk—C5, C6
	Origin	Upper two thirds of the lateral border of the scapula
	Insertion	Greater tubercle of the humerus, capsule of the shoulder joint
	Action	Adduction and external rotation of the shoulder
	Position	Prone, lateral decubitus, or sitting
	Activation	Externally rotate the shoulder.
	Needle placement	This muscle overlies the upper two thirds of the lateral border of the scapula and the lower portion of the glenohumeral joint.

Table 8-27 Brachioradialis (Fig. 8-27)

Figure 8-27 • Brachioradialis	Innervation	Radial nerve—posterior cord—posterior division—upper trunk—C5, C6
	Origin	Proximal two thirds of lateral supracondylar ridge of the humerus
	Insertion	Base of styloid process of the radius
	Action	Flexion of the forearm elbow
	Position	Half-pronation of the wrist, elbow flexed
	Activation	Flex the elbow.
	Needle placement	Place your thumb into the antecubital space and pinch the muscle lateral to your thumb. Insert 2 cm distal to this point.

Table 8-28 Extensor Carpi Radialis (Fig. 8-28)

Figure 8-28 • Extensor carpi radialis	Innervation	Radial nerve—posterior cord—posterior division—upper and middle trunk—C6, C7
	Origin	Lower third of lateral supracondylar ridge of the humerus, lateral epicondyle of the humerus, and radial collateral ligament of the elbow
	Insertion	Extensor carpi radialis longus: posterior aspect of base of the second metacarpal Extensor carpi radialis brevis: posterior aspect of base of the third metacarpal
	Action	Extension and radial abduction of the wrist
	Position	Pronation of the forearm
	Activation	Make a fist (this avoids activation of extensor digitorum).
	Needle placement	Palpate the muscle adjacent to the brachioradialis on the dorsal forearm and insert one third of the distance from the lateral epicondyle to the wrist.

Table 8-29 Supinator (Fig. 8-29)

Figure 8-29 • Supinator	Innervation	Posterior interosseous nerve*—radial nerve—posterior cord—posterior division—upper trunk—C6, C7
	Origin	Lateral epicondyle of the humerus, lateral ligament of elbow joint, annular ligament of the radius
	Insertion	Radial and anterior aspect of upper third of the radius
	Action	Supination of the forearm
	Position	Pronation of the forearm
	Activation	Supinate the forearm.
	Needle placement	With the forearm pronated to extend this muscle, insert 4 cm distal to the lateral epicondyle and deep (you have gone only a little too far when you hit the bone).
	* Also known as deep radial nerve.

Table 8-30 Triceps Brachii (Fig. 8-30)

Figure 8-30 • Triceps brachii	Innervation	Radial nerve—posterior cord—posterior division—middle and lower trunk—C7, C8
	Origin	Long head: infraglenoid tuberosity of the scapula Lateral head: lateral and posterior aspect of the humerus Medial head: lower posterior aspect of the humerus
	Insertion	Upper posterior aspect of olecranon process of the ulna
	Action	Extension of the elbow
	Position	Supine or lateral decubitus, elbow flexed
	Activation	Extend the elbow.
	Needle placement	Insert needle into each head as shown in figure. A thick fat pad overlies this muscle, making it much deeper than other muscles of the upper limb.

Table 8-31 Anconeus (Fig. 8-31)

Figure 8-31 • Anconeus	Innervation	Radial nerve—posterior cord—posterior division—middle and lower trunk—C7, C8
	Origin	Lateral epicondyle of the humerus, posterior ligament of the elbow
	Insertion	Lateral aspect of the olecranon and posterior aspect of the ulna
	Action	Extension of the elbow
	Position	Pronation of the forearm with flexed elbow
	Activation	Extend the elbow.
	Needle placement	This muscle lies between the lateral epicondyle and the ulna just below the olecranon. It is the key to separating radial nerve injuries above and below the elbow.