muscular system

Introduction
All bodily movement is performed by muscle. Bend your arm and move your
hand toward your shoulder. The muscles in your forearm and upper arm have
made this happen. They are called voluntary muscles because you can make
them move when you want them to. At the same time you were doing this, your
heart kept beating even though you were not thinking about it. The heart is an
example of involuntary muscle. It does its job without being told. Major Muscles of the Body
Practice for Learning: Major Muscles of the Body
Write the muscles listed below in the correct spaces in Figure 8-1A and B. To help you,
the number beside the muscle tells you where it goes on the figure. Be sure to pronounce
each word as you write it. Repeat the pronunciation several times if you find the
word hard to say.
Anterior View
1. facial muscles (FAY-shul MUSS-elz)
2. sternocleidomastoid (stern-oh-kleye-doh-MASS-toyd)
3. pectoralis major (peck-tor-AL-iss MAY-jor)
4. serratus anterior (seh-RAY-tuss an-TEER-ee-or)
5. abdominal muscles (ab-DOM-ih-nul)
6. adductors of thigh (ah-DUCK-terz)
7. sartorius (sar-TOR-ee-us)
8. quadriceps femoris (KWAH-drih-seps FEM-or-iss)
9. biceps brachii (BYE-seps BRAY-kee)
Posterior View
10. trapezius (trah-PEE-zee-us)
11. triceps brachii (TRIGH-seps BRAY-kee)
12. latissimus dorsi (lah-TIS-ih-mus)
13. gluteus maximus (GLOO-tee-us MAX-ih-muss)
14. gastrocnemius (gas-troh-NEE-mee-us)
15. Achilles tendon (ah-KILL-eez TEN-don)
16. hamstrings (HAM-stringz)
17. deltoid (DEL-toyd)
The words “biceps” and “triceps” always end in “s,” whether they are
referring to one muscle or more than one.
8.2 T ypes of Muscle Tissue
The cells found in muscle are called muscle fibers. They are long, slender, and threadlike.
They can contract (kon-TRAKT), which means they can shorten their length. This
makes movement possible. Muscle fibers form three types of muscle tissue: cardiac
(KAR-dee-ack), visceral (VISS-er-al), and skeletal (SKEL-eh-tal). Cardiac muscle is
located in the heart and functions to pump blood. Visceral muscles move internal organs
such as the respiratory tract, digestive tract, and blood vessels. Skeletal muscles are
located on top of bone. They move bone by pulling on it.
There are three types of muscle tissue:
cardiac
visceral
skeletal
In Brief
All muscle is wrapped in a band of connective tissue called fascia (FASH-ee-ah), as
illustrated in Figure 8-2. This is called deep fascia.
In this chapter you will learn only about the skeletal muscles.
Movements of Skeletal Muscles
All skeletal muscles are connected to two bones. This makes movement possible. When
the muscle contracts, one of the two bones it is connected to moves because the muscle
pulls on the bone. This is illustrated in Figure 8-3.
The muscles are connected to bones by bands of connective tissue. Some of these
tissues are thin and cordlike. They are called tendons (Figure 8-3). Broader bands of
connective tissues are called aponeuroses (ah-poh-new-ROH-seez).
Types of Muscle Movements
Muscles move bone in different ways. The common movements are listed below and are
illustrated in Figures 8-4 to 8-8.
• Flexion means decreasing the angle between two bones, such as bending the
neck forward or bending a limb.
• Extension means increasing the angle between two bones; it is a return from
flexion.
• Hyperextension means overextending the joint beyond straight (beyond the
anatomical position).
• Abduction means movement away from the midline of the body, usually
involving the upper or lower limbs.
• Adduction means movement toward the midline of the body, usually involving
the upper or lower limbs
Pronation means turning the palm down or backward.
• Supination means turning the palm up or toward the front.
• Eversion means movement of the sole of the foot outward, away from the
midline.
• Inversion means movement of the sole of the foot inward, toward the midline