Medical Terminology For Dummies
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The musculoskeletal system is made up of muscles and joints and, therefore, lots of medical terms. The muscles — all 600 of them and more — are responsible for movement. The skeleton provides attachment points and support for muscles, but it’s the muscle tissue’s ability to extend and contract that makes movement happen. So, for every climb of the elliptical machine, you can thank muscular tissue for making it possible.

Muscles make up the major part of fleshy portions of the body and account for one half of body weight.

Internal movement involves the contraction and relaxation of involuntary muscles, The muscles that provide external movement are known as voluntary muscles, as they perform movements on command.

Classes of muscles

The class system is alive and well, at least as far as your muscles are concerned. There are three classes of muscles: skeletal, visceral, and cardiac.

  • Cardiac (involuntary striated) muscle has branching fibers and forms most of the wall of the heart. Its contraction produces the heartbeat.

  • Skeletal (voluntary striated, meaning striped) muscles, are attached to the skeleton. They are called voluntary, of course, because they are controlled by your will. This type of muscle can be easily seen by flexing the forearm, which makes the biceps muscle become hard and thick.

  • Visceral (involuntary smooth) muscle is found in the stomach, intestines, and blood vessels, and cannot be controlled at will.

Unlike other muscle, cardiac muscle keeps beating even when removed from the body, as in a heart transplant.

Types of muscles

Oh, if it were only that easy. But there are also types of muscles. There are three types of muscles in the body.

Striated muscle

Striated muscles are also called skeletal or voluntary muscles. These are the muscles that move all the bones, as well as the face and the eyes. The body is able to consciously control the activity of a striated muscle.

Smooth muscle

The second type of muscle is smooth muscle, also known as visceral, involuntary or unstriated muscle. The body has no conscious control over smooth muscles, which move the internal organs such as the digestive tract. The smooth muscles are also found in blood vessels and secretory ducts leading from glands.

Skeletal muscle fibers are arranged in bundles, but smooth muscles form sheets of fibers that wrap around tubes and vessels.

Cardiac muscles

The third type of muscle is cardiac muscle. It is striated in appearance but is like smooth muscle in its actions. Movement of cardiac muscle cannot be consciously controlled. Cardiac muscle has branching fibers forming most of the wall of the heart and controlling the contractions producing the heartbeat.

Muscles and tendons

Now that you know the classes and types of muscles, let’s take a more in-depth look at how they work. You already know that skeletal muscles, or striated muscles, are the muscles that move the bones of the body. Now get ready for the scoop on what makes it possible.

When a muscle contracts, one of the attached bones remains stationary, as a result of other muscles holding it in place. The point of attachment of the muscle to the stationary bone is called the origin or beginning of that muscle. When the muscle contracts, another bone to which it is attached, does move. The junction of the muscle to the bone that moves is called the insertion of the muscle.

Near the point of insertion, the muscle narrows and is connected to the bone by a tendon. One type of tendon that helps attach bone to muscles is called an aponeurosis.

Roundup of the superficial muscles

Your superficial muscles are so named because these are the ones you’re most likely to see with the naked eye. These workhorses of the muscular system help make you unique. They help your body perform everyday functions like picking up objects and smiling.

[Credit: Illustration by Kathryn Born]
Credit: Illustration by Kathryn Born
  • Arm muscles consist of the upper arm muscles, biceps brachii and triceps brachii. In the forearm (lower arm) are the flexor and extensor muscles of the hands and fingers.

  • Head and face muscles include the frontalis, temporalis, orbicularis oculi, orbicularis oris, occipitalis, mentalis, buccinator, zygomatic major and minor, and the masseter muscle.

  • Shoulder and neck muscles include the sternocleidomastoid, pectoralis major, latissimus dorsi, and trapezius muscle, leading to the deltoid muscle of the shoulder.

  • The major chest and abdominal muscles consist of the diaphragm, pectoralis major, the rectus abdominis, and the external oblique. Also associated with this region is the linea alba. The linea alba (meaning “white line”) is a vertical band of connective muscular tissue that begins at the xiphoid process (sternum) and ends at the symphysis pubis (where the iliac bones join at the front of the pelvis).

    [Credit: Illustration by Kathryn Born]
    Credit: Illustration by Kathryn Born
  • The major muscles of the back include the seventh cervical vertebral muscle, infraspinatus, supraspinatus, latissimus dorsi, and the rhomboid major muscle.

    [Credit: Illustration by Kathryn Born]
    Credit: Illustration by Kathryn Born

The seventh cervical vertebra muscle is a muscle, whereas the seventh vertebra is a bone. Many muscles, tendons, and ligaments have the same name but don’t have the same function. In this case, the seventh cervical muscle is a point of attachment aiding in support and movement of head and neck.

  • The pelvis and anterior thigh muscles include the tensor fascia lata, the adductors of the thigh, the vastus lateralis and vastus medialis, the rectus femoris, and the quadriceps.

  • The lower leg muscles from the knee to the ankle includes the gastrocnemius, which makes up a large portion of the calf muscles, the tibialis anterior, soleus, peroneus longus, and peroneus brevis. By the way, things aren’t always what they seem: The Achilles tendon is technically classified as a muscle.

  • From the back, the buttocks are composed of the gluteus maximus and gluteus medius. In the thigh are the adductor magnus, vastus lateralis, gracilis, whereas the biceps femoris, semitendinosus and semimembranosus combined comprise the hamstrings.

    [Credit: Illustration by Kathryn Born]
    Credit: Illustration by Kathryn Born

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