Las Positas College



Chapter 11

Muscles of the Body

I. Lever Systems: Bone-Muscle Relationships (pp. 259–263, Figs. 11.1–11.2)

A. Define lever, fulcrum, load (resistance), and effort (applied force); distinguish between first-class lever, second-class lever, and third-class lever relationships; in the human body, bones are the levers, joints are the fulcrums, and the effort is exerted by skeletal muscles pulling on their insertions.

B. Most muscles in the human body are third-class lever systems that provide speed of movement.

II. Arrangements of Fascicles in Muscles (pp. 261–262, Fig. 11.3)

A. Muscles have different shapes and actions because of different arrangements of fascicles; patterns of fascicles are circular, parallel, convergent, and pennate.

B. The arrangement of fascicles influences the range of movement and the power of a muscle.

III. Organizational Scheme Based on Embryonic Development (pp. 262–264, Fig. 11.4)

A. Skeletal muscles have specific embryonic origins, though all arise from mesoderm.

B. The first seven myotome-like structures of the head are somitomeres.

C. The development-based scheme organizes muscles into four groups.

1. Musculature of the visceral organs

2. Pharyngeal arch muscles

3. Axial muscles

4. Limb muscles

IV. Skeletal Muscle Interactions (p. 264)

A. Muscles are classified into functional types with respect to their actions; these classes include prime movers (agonists), antagonists, synergists, and fixators.

B. Opposing groups of skeletal muscles are arranged across movable joints so that one group can reverse or modify the action of the other group.

V. Muscle Compartments of the Limbs (pp. 264–270)

A. Dense fibrous connective tissue divides the limb muscles into compartments.

B. Muscles in opposing compartments act as agonist/antagonist pairs.

C. A single named nerve usually innervates each compartment.

D. The upper limb has two compartments: anterior and posterior.

E. The thigh is divided into three compartments: anterior, posterior, and medial.

F. The leg is divided into three compartments: anterior, posterior, and lateral.

VI. Naming of Skeletal Muscles (p. 271)

A. Names of muscles provide information about the muscle; several criteria are location, shape, relative size of the muscle, direction of the fascicles and muscle fibers, location of attachments, number of origins, and actions.

VII. Major Skeletal Muscles of the Body (pp. 272–326, Figs. 11.6–11.25, and Tables 11.1–11.17)

A. There are 600+ muscles in the human body; understanding all the body movements previously covered is required to master human musculature.

B. Refer to p. 266 for a well-organized and comprehensive list of tables and figures covering hundreds of human muscles.

C. Primary features of the tables include the muscle name, description, origin and insertion, action, nerve supply, and basic summary of regional muscles covered in the table.

VIII. Regional Surface Anatomy (pp. 326–340)

A. Surface anatomy forms the foundation for clinical assessment of body structures, usually by an integrated regional approach.

B. Surface anatomy is the study of external landmarks of the body and of the internal structures that may be observed or palpated through the body surface.

IX. The Head (pp. 326–328, Fig. 11.26)

A. The head is divided into the cranium and face.

B. The cranium has numerous bony and muscular structures that may be palpated through the skin. Among the cranial structures are the superciliary arches, mastoid process of the temporal bone, external occipital protuberances, and temporalis muscle.

C. Facial structures are further divided into the orbital, nasal, auricular, and oral regions. Facial structures that may be palpated through the skin include the zygomatic arch, bridge of the nose, temporomandibular joint, and the body of the mandible.

X. The Neck (p. 328, Figs. 11.27 and 11.28)

A. Skeletal landmarks of the neck include the hyoid bone, the spine of C7 vertebra, and the laryngeal prominence.

B. Muscles of the neck include the sternocleidomastoid muscles and a portion of the trapezius.

C. The neck is divided into anterior and posterior triangles.

1. The boundaries of the anterior triangle are the inferior margin of the mandible, midline of the neck, and sternocleidomastoid.

2. The boundaries of the posterior triangle are the clavicle, sternocleidomastoid, and trapezius.

XI. The Trunk (pp. 328–330, Figs. 11.29 and 11.30)

A. The trunk consists of the thorax, abdomen, pelvis, and perineum.

B. The thorax presents numerous landmarks for locating bones, muscles, and internal organs.

1. The sternum and ribs are the bony landmarks of the thorax and the costal margin marks the inferior boundary of the thorax.

2. The prominent muscles of the thorax are the pectoralis major and the serratus anterior.

C. The abdomen is located inferior to the diaphragm.

1. Bony landmarks include the iliac crest, anterior superior iliac spine, and pubic crest.

2. Muscles and other abdominal surface features include the linea alba, rectus abdominis, inguinal ligament, and umbilicus.

D. The pelvis and perineum include bony and surface features. Among them are the ischial tuberosities, the coccyx, and the external genitalia.

XII. The Back (pp. 330–332, Fig. 11.31)

A. Bony structures of the back that may be palpated include the vertebral spinous processes, spines of the scapulae, and iliac crests.

B. Prominent muscles of the back include the trapezius, latissimus dorsi, and erector spinae.

XIII. The Upper Limb and Shoulder (pp. 332–335, Figs. 11.32 – 11.36)

A. The axilla is the armpit. The anterior axillary fold is formed by the pectoralis major muscle, while the posterior axillary fold is formed by the latissimus dorsi.

B. Shoulder palpation reveals the locations of the acromion, the clavicle, greater tubercle of the humerus, and the deltoid muscle.

C. The arm is the upper portion of the upper limb, formed by the humerus and underlying muscles. Muscles in the arm regions are the biceps brachii and triceps brachii.

D. The elbow region is characterized anteriorly by the cubital fossa (antecubital fossa). The lateral and medial epicondyles of the humerus form the lateral and medial boundaries of the elbow, while the olecranon process of the ulna forms the posterior point of the elbow.

E. The forearm and hand are comprised of the ulna, radius, carpals, metacarpals, and phalanges.

XIV. Lower Limb and Gluteal Region (pp. 336–340, Figs. 11.37–11.41)

A. The gluteal region is dominated by the “cheeks” of the buttocks, formed primarily by the gluteus maximus muscles.

B. Bony landmarks of the thigh include the greater trochanter of the femur, medial and lateral condyles of the femur, and patella. Muscular landmarks are the femoral triangle and popliteal fossa.

C. The leg and foot are home to several bony landmarks. Among them are the tibial tuberosity, medial malleolus, lateral malleous, and head of the fibula.

SUPPLEMENTAL STUDENT MATERIALS to Human Anatomy, Fifth Edition

Chapter 11: The Muscular System

To the Student

In previous chapters, you learned about the skeleton, joints, movements, and muscle tissues. Now it is time to study the skeletal muscles of the body. Chapter 11 explores the bone–muscle relationships and is a culmination of things learned in Chapters 7–10. Movements are determined by muscle attachments to bone, lever systems, arrangement of fascicles, and skeletal muscle group interactions. Many muscles are listed in the Muscle Gallery Tables, and your instructor will tell you which individual muscles you must learn. Keep in mind that muscles act in groups to perform specific functions, such as flexion or extension, and rarely, if ever, act individually. For simplicity, you will examine individual muscles, learning their origins, insertions, actions, and possibly the innervations of each. The proper way to study muscles initially is not through memorization, but a thorough understanding of origin, insertion, and action. If needed, review movements covered in Chapter 9.

Primarily, your study of anatomy incorporated the systemic approach, until this chapter. Now you have the unique opportunity to combine everything you have studied by using an anatomical regional approach. There is a chance you looked at the skeleton and muscle information in this chapter when your instructor covered those topics earlier. Nevertheless, a wonderful summary and “put-it-all-together” concept pervades this chapter. The regional approach of this chapter enables you to better understand the relationships between muscles, bones, blood vessels, lymph nodes, nerves, internal organs, and sites of injections, drawing blood, and inserting tubes. Whether your career goal is a health care profession or not, it is to your advantage to be able to understand the normal body in order to detect something that is abnormal. Careful observation and knowledge of palpation techniques will aid this understanding. And, do not forget, your own body is the best “cheat sheet” possible in anatomy. It is the one thing you cannot leave behind when you go into the classroom for your exam!

Step 1: Describe lever systems and their relationships to bone and muscle.

- Define lever.

- Distinguish between effort, fulcrum, and load.

- Explain the conceptual relationship of leverage to bone, joints, and muscle.

- Describe first-class, second-class, and third-class levers.

- Explain why most lever systems in the body are third-class.

Step 2: Summarize the different arrangements of fascicles in muscles.

- Describe the parallel pattern of arrangement and name an example.

- Describe convergent pattern of arrangement and name an example.

- Describe pennate (unipennate, bipennate, and multipennate) patterns of arrangement and name examples.

- Describe the circular pattern of arrangement and name an example.

Step 3: Summarize skeletal muscle group interactions in the body.

- Define and give an example of a prime mover (agonist).

- Define and give an example of an antagonist.

- Define and give an example of a synergist.

- Define and give an example of a fixator.

Step 4: Understand the naming of skeletal muscles.

- List criteria for the naming of skeletal muscles.

- Give an example of a muscle that fits each criterion listed.

Step 5: Organize the body’s muscles into functional groups based on developmental origins.

- Distinguish between myotomes and somitomeres.

- Explain the developmental-based scheme for the development of musculature of the visceral organs.

- Describe the developmental-based scheme for the development of pharyngeal arch muscles.

- Describe the developmental-based scheme for the development of axial muscles.

- Explain the developmental-based scheme for the development of limb muscles.

Step 6: Focus on specific skeletal muscles and respective groups described in Muscle Gallery 11.1–11.17 as assigned by your instructor.

- List criteria for determining the origin and insertion of a muscle.

- Make sure you understand all the body movements detailed in Figures 9.5 and 9.6.

- Describe the action of each assigned muscle and explain the action based on the origin and insertion of the muscle.

- Design flash cards for assigned muscles, including muscle shape, location, attachments, actions, and innervation.

Step 7: Describe surface anatomy as a field of study.

- Define surface anatomy.

- Explain the importance of surface anatomy to the “living” body.

- Define palpation.

- Distinguish between systemic and regional approaches to the study of anatomy.

- List several ways surface anatomy provides information for a clinician.

Step 8: Describe the major surface features of the head.

- Distinguish between the cranium and the face.

- Palpate major surface features of the cranium as described by your textbook.

- Distinguish between the cranium and the scalp.

- Palpate major surface features of the face as described by your textbook.

Step 9: Describe and palpate the major surface features of the neck.

- Palpate the major skeletal landmarks of the neck as described by your textbook.

- Palpate the major muscles of the neck.

- Define and describe the anterior and posterior triangles.

- Using the triangles of the neck as a reference, describe locations for palpations of a pulse, the larynx, cervical lymph nodes, and the trachea.

- Sketch the anterior and posterior triangles, labeling important surface features.

- List at least three vitally important structures that lie deep in the neck, explaining why they are so important.

Step 10: Describe and palpate the major surface features of the trunk.

- Define the back, and count and palpate vertebral processes, naming the easy ones to find as landmarks.

- Distinguish between the posterior median fissure and the supracrestal line.

- Define and describe the posteriorly located triangle of auscultation, explaining the clinical significance of this area.

- Explore the anterior thoracic surface, palpating all bony and muscular features described in your textbook.

- Distinguish between the midaxillary line and the midclavicular line.

- Map the location of the pleural cavities, the lungs, and the heart using the ribs as a reference.

- List and palpate all features of the anterior abdominal wall listed in your textbook.

- Define umbilicus, and explain the examination for an inguinal hernia.

- Define linea alba, explaining why this is a site of clinical significance.

- Describe the location of McBurney’s point, explaining why this is a site of clinical significance.

- Distinguish between linea semilunaris and tendinous intersections.

- Explain the clinical significance of a physician placing a stethoscope on the abdominal wall, describing the sites of placement and the clues various sounds provide.

- Describe the bony boundaries of the perineum.

Step 11: Describe and palpate the major surface features of the upper limb and shoulder.

- Define axilla, naming important superficial structures associated with this part of the body.

- Explain why women should palpate the axilla during a breast self-examination.

- Identify and palpate the bony landmarks of the shoulder.

- Identify an upper limb location for an intramuscular injection.

- Identify and palpate the bony and muscular surface features of the arm.

- Identify and palpate the bony landmarks of the elbow region.

- Explain where and why you feel a tingling sensation if you bump your elbow, or in more common vernacular, “hit your crazy/funny bone.” (And, be careful with your explanation because the reference is not to your “humerus.”)

- Define and describe the cubital fossa and explain the clinical significance of the median cubital vein.

- Describe and palpate the bony and muscular structures of the forearm and hand listed in your textbook.

- Assume the anatomical position, then pronate your hand and identify which forearm bone remains more stationary.

- Make a clinched fist, and identify either one or both of the tendons evident on the anterior wrist.

- Describe and palpate pulse points in the distal forearm.

- Identify an important site for drawing blood and administering an IV distally on the upper extremity.

Step 12: Describe and palpate the major surface features of the lower limb and gluteal region.

- Identify and palpate the bony landmarks of the gluteal region.

- Distinguish between the natal cleft and the gluteal fold.

- Explain the clinical procedures and concerns for administering intramuscular injections in the gluteal region, i.e., the “safe area.”

- List and palpate the bony and muscular landmarks of the thigh.

- Explain the femoral triangle and describe the clinical significance of this area.

- Define and palpate the popliteal fossa.

- List and palpate the bony landmarks of the leg and foot described in your textbook.

- Identify the location of the pulse of the posterior tibial artery and the dorsalis pedis artery.

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