The Study of Skeletal Muscles

Objectives

When you have completed this section, you should be able to

• explain why a knowledge of muscular anatomy is important in a variety of professions; and
• interpret Latin words used in the naming of muscles.

Key Point Review

1. Name at least five criteria by which muscles are named.

2. In muscle names, what do the words brevis, teres, digitorum, pectoralis, triceps, and profundus mean?

Functions and Structural Organization of Muscles

Objectives

When you have completed this section, you should be able to

• list the functions of the muscular system;
• identify the connective tissue components of a skeletal muscle and explain how they contribute to the organization of the muscle;
• describe some anatomical features that most skeletal muscles have in common;
• classify muscles according to the orientation of their fascicles; and
• explain how skeletal muscles can work together to produce coordinated movements at a joint.

Key Point Review

3. List some of the functions of muscles other than moving the body or its individual parts.

4. Describe four layers of fibroconnective tissue associated with a skeletal muscle.

5. Explain why a muscle does not easily pull loose from a bone, even under great stress.

6. Define the terms origin, insertion, belly, action, and innervation.

7. Describe the five basic shapes of muscles.

8. Explain the function of prime movers, synergists, antagonists, and fixators.

Muscles of the Head and Neck

Objectives

When you have completed this section, you should be able to

• name and locate the muscles that produce facial expressions;
• name and locate the muscles used for chewing and swallowing;
• name and locate the neck muscles that move the head; and
• state the origin, insertion, and action of any head or neck muscles.

Think About It

Of the muscles you have studied so far, name three that you would consider intrinsic muscles of the head and three that you would classify as extrinsic. Give the reasons for your classification.

Key Point Review

9. What are the two divisions of the epicranius and what do they do?

10. Name any two muscles that elevate the upper lip and two that depress the lower lip.

11. Name the four muscles of mastication and state where they insert on the mandible.

12. Distinguish between the functions of suprahyoid and infrahyoid muscles.

13. Identify the prime movers of head flexion and extension.

Muscles of the Trunk

Objectives

When you have completed this section, you should be able to

• name and locate the muscles that ventilate the lungs and explain how they affect abdominal pressure; and
• name and locate the muscles of the abdominal wall, spinal column, and pelvic floor.

Think About It

If you eat spare ribs, what muscles are you eating?

Key Point Review

14. Which muscles are used more often–the external intercostals or internal intercostals? Why?

15. Explain how pulmonary ventilation affects abdominal pressure and vice versa.

16. Describe the relationship of the abdominal aponeurosis to the rectus sheath, linea alba, and inguinal ligament.

17. Name a major superficial muscle and two major deep muscles of the back.

18. Define perineum, urogenital triangle, and anal triangle.

19. Name one muscle in each of the following regions: pelvic diaphragm, urogenital diaphragm, and superficial perineal space.

Muscles Acting on the Upper Extremity

Objectives

When you have completed this section, you should be able to

• name and locate the muscles that move the pectoral girdle, arm, forearm, and hand; and
• describe the origins, insertions, and actions of these muscles.

Think About It

Earlier it was remarked that since a muscle can only pull (not push), antagonistic pairs of muscles are necessary to produce opposite actions at a joint. Reconcile this fact with the observation that the deltoid muscle both flexes and extends the shoulder.

Think About It

Why are the prime movers of finger extension and flexion located in the forearm rather than in the hand, closer to the fingers?

Key Point Review

20. Name a muscle that inserts on the scapula and plays a significant part in (a)pushing a stalled car, (b)paddling a canoe, (c)squaring the shoulders in military attention, (d)lifting the shoulder to carry a heavy box on it, and (e)lowering the shoulder to pick up a suitcase.

21. Describe three contrasting actions of the deltoid muscle.

22. Name the four rotator cuff muscles and describe the scapular surfaces against which their bellies lie.

23. Name the prime movers of elbow flexion and extension.

24. State three different functions of the biceps brachii.

25. Name three extrinsic muscles and two intrinsic muscles that flex the phalanges.

Muscles Acting on the Lower Extremity

Objectives

When you have completed this section, you should be able to

• identify the muscles that act on the thigh, leg, and foot; and
• state the action, origin, insertion, and innervation of these muscles.

Think About It

What muscles are used for the downstroke in pedaling a bicycle? Why are racing bicycles designed to make the rider lean forward?

Key Point Review

26. In the middle of a stride, you have your left foot on the ground and you are about to swing your right leg forward. What muscles produce the motion of the right leg?

27. Name some muscles whose tendons cross both the hip and knee joints and act on both.

28. List the major actions performed by muscles of the anterior, medial, and posterior compartments of the thigh.

29. What is the role of plantar flexion and dorsiflexion in walking? Which muscles produce these actions?

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