1. Most of this chapter is devoted to a descriptive inventory of the body's muscles.

2. In 1895, Latin was chosen as the official language for muscle nomenclature. Terms used in this text are English modifications of the Latin names.

1. Suggestions for study of muscles include: using visual images, palpate muscles on yourself, locate origins and insertions on a skeleton, study the derivation of each muscle name, and say the names aloud.

1. Muscle functions include: movement, communication (enable speech, writing), stability, control of body openings, and heat production.

1. Skeletal muscle cells, called fibers, are each surrounded by a thin layer of aerolar tissue called the endomysium.

2. Muscle fibers are grouped into bundles, called fascicles, each of which is surrounded by a connective tissue sheath, the perimysium.

3. Each whole muscle is covered by yet another layer of connective tissue, the epimysium. The epimysium grades into fascia.

4. Muscles can attach to bone directly through collagen fibers between the epimysium and periosteum, or indirectly through extensions of deep fascia called tendons.

1. A muscle attachment at the stationary end is the origin; the relatively movable end is the insertion. The thicker middle region is the belly of the muscle.

2. Fusiform muscles are thick in the middle and taper at each end.

3. Parallel muscles are long, strap-like muscles of uniform width and parallel fascicles.

4. Convergent muscles are fan-shaped.

5. Pennate muscles are feather-shaped. Pennate muscles can be unipennate, multipennate, or bipennate.

6. Circular muscles (sphincters) surround body openings.

1. The movement of a muscle is its action; muscles seldom act alone.

2. The prime mover (agonist) is the muscle producing the most force.

3. The antagonist is a muscle that opposes the prime mover. An antagonistic pair of muscles act on opposite sides of a joint.

4. A fixator is a muscle that prevents the movement of a bone.

1. An intrinsic muscle is entirely contained within a particular region.

2. An extrinsic muscle acts upon a designated region but has its origin elsewhere.

1. Innervation refers to the nerve supply to an organ. Knowing the innervation to a muscle enables the diagnosis of nerve and spinal cord injuries from their effects on the muscle.

1. Humans have an amazing variety of facial expressions when compared with other animals.

2. The frontalis (forehead) and occipitalis (at back of head) collectively are the epicranius, attached across the top of the skull by the galea aponeurotica.

3. The orbicularis oculi closes the eyelid, while the levator palpebrae superioris opens it. Other muscles of the eye and nose areas are the corrugator supercilii, procerus, and nasalis.

4. A sphincter, the orbicularis oris, surrounds the mouth. Five muscles approach the orbicularis oris from all directions. These are the levator labii superioris alaeque nasi, the levator labii superioris, the zygomaticus minor, zygomaticus major, and the risorius.

5. Muscles that draw the lower lip downward are the depressor anguli oris, the depressor labii inferioris, and a pair of mentalis muscles.

6. The buccinator muscle of the cheek helps in suckling and chewing (pushing food against the teeth).

7. The platysma under the chin depresses the mandible, widens the mouth, and tenses the neck.

1. Extrinsic muscles that connect the tongue to other structures in the head and neck are the genioglossus, hyoglossus, styloglossus, and palatoglossus.

2. The four paired muscles of mastication are the temporalis, masseter, and medial and lateral pterygoid muscles.

3. Eight hyoid muscles aid in chewing and swallowing. Four are superior to the hyoid: digastric, geniohyoid, mylohyoid, and stylohyoid. The inferior group includes the omohyoid, sternohyoid, sternothyroid, and thyrohyoid.

4. When food enters the mouth, the superior, middle, and inferior pharyngeal constrictors contract in that order to force the bolus downward.

1. The principle flexors of the head are the sternocleidomastoid, and the anterior, middle, and posterior scalenes.

2. The extensors of the head are located in the back of the neck. Three primary extensors are the trapezius, the splenius capitis, and the semispinalis capitis.

1. The lungs are ventilated primarily by the diaphragm, which forms the floor of the thoracic cavity; 11 pairs of external intercostal muscles between the ribs; and 11 pairs of internal intercostal muscles between the ribs deep to the external intercostals.

1. The anterior and lateral walls of the abdomen have four pairs of sheet-like muscles that support the viscera and stabilize the spinal column. They are the rectus abdominis, the external and internal obliques, and the transverse abdominis.

2. The right and left rectus muscles are separated by a vertical fibrous strip called the linea alba.

1. Muscles acting on the spine include a superficial group (the erector spinae), divided into three columns: the iliocostalis thoracis, logissimus thoracis, and spinalis thoracis.

2. The major deep muscle is the semispinalis, the two lower sections of which are the semispinalis cervicis and semispinalis thoracis.

3. The major deep lumbar muscle is the quadratus lumborum.

1. The floor of the pelvic cavity is formed by three layers of muscles and fascia that span the pelvic outlet and support the viscera.

2. The superficial perineal space contains the isciocavernosus and bulbospongiosus that function mostly during sexual intercourse.

3. The middle layer of the pelvic floor is spanned by the urogenital diaphragm, composed of a membrane and two muscles, the deep tranverse perineus and the external urethral sphincter.

4. The deepest layer of the pelvic floor (pelvic diaphragm) consists of the levator ani and coccygeus in both sexes.

1. The muscles that act on the pectoral girdle are divided into anterior and posterior groups.

2. Anterior group muscles include the pectoralis minor and serratus anterior.

3. The posterior group consists of a superficial muscle, the trapezius, and three deep muscles, the levator scapulae, and rhomboideus major and minor.

1. Nine shoulder muscles cross the shoulder joint ad insert on the humerus.

2. Two axial muscles are the pectoralis major (flexor) and latissimus dorsi (extensor). These are the prime movers of the shoulder joint.

3. Three of the 7 scapular muscles are the deltoid (primer mover that flexes, extends, and abducts the shoulder), the teres major (extensor), and coracobrachialis (flexor and adductor). The remaining four form the rotator cuff: the infraspinatus, supraspinatus, subscapularis, and teres major.

1. The prime flexors are the biceps brachii and brachialis. The brachioradialis is a synergist in elbow flexion.

2. The prime extensor is the triceps brachii with a weak synergistic anconeus.

3. Pronation is achieved by the pronator teres and pronator quadratus.

4. Supination is achieved by the biceps brachii and the supinator.

1. The hand is acted upon both by extrinsic muscles located in the forearm and intrinsic muscles of the hand itself.

2. Refer to Table 11.14 for a list of the forearm muscles, divided into anterior and posterior compartments.

1. The intrinsic muscles are divided into three groups and are contained entirely within the hand: thenar muscles, hypothenar muscles, and the midpalmar group.

1. Most of the muscles acting on the femur originate on the os coxae.

2. Two principle anteror flexors are the iliacus and psoas major.

3. Three posterolateral extensors are the gluteus maximus, gluteus medius, and tensor fasciae latae.

1. The muscles of the thigh move the lower leg.

2. The anterior extensors are the large quadriceps femoris, and its four heads: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. All four converge on the patellar tendon.

3. Crossing the quadriceps from lateral to medial side is the sartorius (flexor).

4. Five medial muscles act on the hip joint: adductor longus, adductor brevis, adductor magnus, gracilis, and pectineus.

5. Muscles of the posterior compartment are the biceps femoris, semimembranosus, and semitendinosus.

1. The anterior dorsiflexors are the extensor digitorum longus, extensor hallucis longus, peroneus tertius, and tibialis anterior.

2. The posterior compartment has three superficial plantar flexors: gastrocnemius, soleus, and plantaris.

3. Deep flexors are the flexor digitorum longus, flexor hallucis longus, tibialis posterior, and popliteus.

4. The lateral group consists of the peroneus brevis and peroneus longus that plantar flex and evert the foot.

1. The intrinsic muscles of the foot support the arches and aid in locomotion. The superficial muscles are the extensor digitorum brevis, flexor digitorum brevis, quadratus plantae, and four lumbrical muscles.

2. Deeper muscles include the adductor hallucis, flexor digiti minimi brevis, and flexor hallucis brevis.

3. The deepest layer consists of four dorsal and three plantar interosseous muscles.