Appendicular Muscles 355
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MUSCULAR SYSTEM OUTLINE 12.1 Muscles That Move the Pectoral Girdle and Upper Limb 355 12.1a Muscles That Move the Pectoral Girdle 355 12 12.1b Muscles That Move the Glenohumeral Joint/Arm 360 12.1c Arm and Forearm Muscles That Move the Elbow Joint/Forearm 363 12.1d Forearm Muscles That Move the Wrist Joint, Appendicular Hand, and Fingers 366 12.1e Intrinsic Muscles of the Hand 374 12.2 Muscles That Move the Pelvic Girdle and Lower Limb 377 Muscles 12.2a Muscles That Move the Hip Joint/Thigh 377 12.2b Thigh Muscles That Move the Knee Joint/Leg 381 12.2c Leg Muscles 385 12.2d Intrinsic Muscles of the Foot 391 MODULE 6: MUSCULAR SYSTEM mck78097_ch12_354-396.indd 354 2/14/11 3:25 PM Chapter Twelve Appendicular Muscles 355 he appendicular muscles control the movements of the upper 2. Identify the muscles that move the scapula and their actions. T and lower limbs, and stabilize and control the movements 3. Name the muscles of the glenohumeral joint, and explain of the pectoral and pelvic girdles. These muscles are organized how each moves the humerus. into groups based on their location in the body or the part of 4. Locate and name the muscles that move the elbow joint. the skeleton they move. Beyond their individual activities, these 5. Identify the muscles of the forearm, wrist joint, fingers, muscles also work in groups that are either synergistic or antago- and thumb. nistic. Refer to figure 10.14 to review how muscles are named, and Muscles that move the pectoral girdle and upper limbs are recall the first Study Tip! from chapter 11 that gives suggestions organized into specific groups: (1) muscles that move the pectoral for learning the muscles. girdle; (2) muscles that move the glenohumeral joint/arm; (3) arm and forearm muscles that move the elbow joint/forearm; (4) fore- arm muscles that move the wrist joint, hand, and fingers; and 12.1 Muscles That Move the Pectoral (5) intrinsic muscles of the hand. Some of these muscles are Girdle and Upper Limb superficial, and others are deep. Learning Objectives: 12.1a Muscles That Move the Pectoral Girdle 1. Describe the major movements of the pectoral girdle and The muscles of the pectoral girdle originate on the axial skeleton upper limb, and indicate the muscles involved for each and insert on the scapula and clavicle (figures 12.1 and 12.2). movement. These muscles both stabilize the scapula and move it to increase Superficial Deep Trapezius Deltoid (cut) Subclavius Deltoid Subscapularis Pectoralis minor Pectoralis major Pectoralis major (cut) Deltoid (cut) Teres major Serratus anterior Latissimus dorsi Latissimus dorsi Long head Biceps brachii Short head Coracobrachialis Anterior view Figure 12.1 Anterior Muscles Associated with the Proximal Upper Limb. This anterior view compares some components of both the axial and appendicular musculature. Only those muscles that move the upper limb are labeled. Superficial muscles are shown on the right side of the body, and deep muscles are shown on the left side. mck78097_ch12_354-396.indd 355 2/14/11 3:25 PM 356 Chapter Twelve Appendicular Muscles Superficial Deep Trapezius Levator scapulae Rhomboid minor Supraspinatus Deltoid Infraspinatus Teres minor Rhomboid major Teres minor Teres major Teres major Serratus anterior Latissimus dorsi Serratus posterior inferior External oblique Posterior view Figure 12.2 Posterior Muscles Associated with the Proximal Upper Limb. This posterior view compares some components of both the axial and appendicular musculature. Only those muscles that move the upper limb are labeled. Superficial muscles are shown on the left, and deep muscles are shown on the right. classified according to their location in the thorax as either ante- Study Tip! rior or posterior thoracic muscles. The anterior thoracic muscles are the pectoralis minor, When studying appendicular muscle function, remember these serratus anterior, and subclavius (shown in figure 12.4a). The two basic rules: pectoralis minor is a thin, flat, triangular muscle deep to the pec- 1. If a muscle crosses over or spans a joint, it must move that toralis major. The muscle helps depress and protract (pull anteri- joint. For example, since the biceps brachii crosses over the orly) the scapula. When your shoulders are hunched forward, the elbow joint, it must move the elbow joint. pectoralis minor muscle is contracting. The serratus anterior is 2. Conversely, if a muscle doesn’t cross over or span a joint, it a large, flat, fan-shaped muscle positioned between the ribs and cannot move that joint. For example, the deltoid is found the scapula. Its name is derived from the saw-toothed (serrated) in the shoulder, and it does not cross over the wrist joint. appearance of its origins on the ribs. This muscle is the prime Therefore, there is no possible way the deltoid can move the wrist joint! mover (agonist) in scapula protraction, and thus works with the pectoralis minor. It is also the primary muscle that helps stabi- If you can visualize where a muscle is located in your body, you lize the scapula against the posterior side of the rib cage and is can usually figure out what type of movement the muscle performs. a powerful superior rotator of the scapula by moving the glenoid cavity superiorly, as occurs when you abduct the upper limb. The subclavius is a small, cylindrical muscle named for its location the arm’s angle of movements. Some of the superficial muscles of inferior to the clavicle. It extends from the first rib to the clavicle, the thorax are grouped together according to the scapular move- and its main action is to stabilize and depress the clavicle. ment they direct: elevation, depression, protraction, or retraction The posterior thoracic muscles are the trapezius, levator scap- (figure 12.3). The muscles that move the pectoral girdle are ulae, rhomboid minor, and rhomboid major (shown in figure 12.4b). mck78097_ch12_354-396.indd 356 2/14/11 3:25 PM Chapter Twelve Appendicular Muscles 357 Protractors Pectoralis minor Serratus anterior Figure 12.3 Actions of Some Thoracic Muscles on the Scapula. Retractors Individual muscles may contribute to different, multiple Trapezius Rhomboids actions. (a) The scapula can be retracted or protracted. When you are standing upright and have good posture, your scapulae are retracted. Conversely, poor posture demonstrates scapular protraction. (b) Muscles that elevate and depress the scapula. (c) Muscles that rotate the scapula. Retracted scapulae Protracted scapulae (“good posture”) (“poor posture”) (a) Retraction and protraction of scapula Elevators Depressors Superior rotators Inferior rotators Rhomboid major Trapezius (inferior part) Serratus anterior Rhomboid major Rhomboid minor Pectoralis minor (not shown) Trapezius (superior part) Rhomboid minor Levator scapulae Levator scapulae Trapezius (superior part) (b) Elevation and depression of scapula (c) Superior and inferior rotation of scapula The trapezius is a large, flat, diamond-shaped muscle that As its name implies, its primary action is to elevate the scapula. extends from the skull and vertebral column to the pectoral girdle It can also inferiorly rotate the scapula so that the glenoid cavity laterally. In general, the trapezius can elevate, depress, retract, or points inferiorly. rotate the scapula, depending upon which fibers of the muscle are Both the rhomboid minor and the rhomboid major are actively contracting. The superior fibers of the trapezius elevate located deep to the trapezius. These rhomboid muscles are paral- and superiorly rotate the scapula. The middle fibers work with lel bands that run inferolaterally from the vertebrae to the scap- the rhomboid muscles to retract the scapula, while the inferior ula. Often they are indistinct from each other. They help elevate fibers depress the scapula. and retract (adduct) the scapula, as when you stand up straight The levator scapulae is a narrow, elongated muscle that is with your shoulders back. The rhomboid muscles also inferiorly deep to both the trapezius and sternocleidomastoid muscles. It rotate the scapula. originates from multiple heads on the transverse processes of the Table 12.1 summarizes the characteristics of the thoracic cervical vertebrae and inserts on the superior angle of the scapula. muscles that move the pectoral girdle. mck78097_ch12_354-396.indd 357 2/14/11 3:25 PM Superficial Deep Sternocleidomastoid Subclavius Subscapularis Deltoid Coracobrachialis Pectoralis minor Pectoralis major Serratus anterior Biceps brachii, long head Sternocleidomastoid Subclavius Deltoid Subscapularis Coracobrachialis Pectoralis major Pectoralis minor Biceps brachii, Serratus anterior long head (a) Anterior view Figure 12.4 Muscles That Move the Pectoral Girdle and the Glenohumeral Joint/Arm. Illustrations and cadaver photos show (a) anterior and (b) posterior views of the muscles whose primary function is to move the pectoral girdle (scapula or clavicle), labeled in bold. Muscles that attach to the pectoral girdle but primarily move the arm are labeled but not in bold. Superficial muscles are shown on the right side of the body and deep muscles on the left. CLINICAL VIEW Paralysis of the Serratus Anterior anterior is the primary protractor of the scapula, and under normal circum- Muscle (“Winged Scapula”) stances, its pull on the scapula is counterbalanced by the posterior thoracic (superficial back) muscles. Paralysis of the serratus anterior muscle leaves The serratus anterior muscle receives its innervation from the long thoracic the posterior thoracic muscles unopposed. If a patient with this condition nerve, which travels inferiorly along the anterolateral chest wall. Because of puts both arms anteriorly on a wall and then pushes, the scapula on the its location, the long thoracic nerve is occasionally damaged or cut during injured side will poke posteriorly like a bird’s wing, a classic sign known as surgical removal of the breast (radical mastectomy). Damage to this nerve the “winged scapula.” The scapula on the unaffected side will remain in the causes paralysis of the serratus anterior muscle.