MSM - Major Muscles and Disorders of the Muscular System Lesson
Major Muscles and Disorders of the Muscular System
Muscle Groups
The over 600 muscles in the body make up around 40 percent of a person's body weight. Most skeletal muscles have names that describe some feature of the muscle.
Associating a muscle's characteristics with its name makes it easier to learn and remember them.
The following table outlines some of the common terms relating to muscle features used to name muscles:
Characteristic | Term | Meaning |
Size | Vastus | Huge |
Maximus | Large | |
Longus | Long | |
Minimus | Small | |
Brevis | Short | |
Shape | Deltoid | Triangular |
Rhomboid | Like a rhombus | |
Latissimus | Wide | |
Teres | Round | |
Trapezius | Like a trapezoid | |
Direction of Fibers | Rectus | Straight |
Transverse | Across | |
Oblique | Diagonally | |
Orbicularis | Circular | |
Location | Pectoralis | Chest |
Gluteus | Buttock or rump | |
Brachii | Arm | |
Supra- | Above | |
Infra- | Below | |
Sub- | Under or beneath | |
Lateralis | Lateral | |
Number of Origins | Biceps | Two heads |
Triceps | Three heads | |
Quadriceps | Four heads | |
Origin and Insertion | Sternocleidomastoideus | Origin on the sternum and clavicle, insertion on the mastoid process |
Brachioradialis | Origin on the brachium or arm, insertion on the radius | |
Action | Abductor | To abduct a structure |
Adductor | To adduct a structure | |
Flexor | To flex a structure | |
Extensor | To extend a structure | |
Levator | To lift or elevate a structure | |
Masseter | To chew |
Muscles of the Head and Neck
Muscles in the head and neck are responsible for facial expression, movement of the head and neck, and chewing.
The muscles responsible for chewing are some of the strongest in the body.
Muscles of the Trunk
The muscles of the trunk include those that move the vertebral column, the muscles that form the thoracic and abdominal walls, and those that cover the pelvic outlet.
These muscles are responsible for maintaining posture, breathing, and protection of organs in the abdominal cavity.
Muscles of the Upper Extremity
Muscles are responsible for attaching the scapula to the thorax and the movement of the scapula, arm, forearm wrist, hand, and fingers.
Muscles of the Lower Extremity
Muscles of the lower extremity are responsible for the movement of the thigh, calf, foot, and toes.
Disorders of the Muscular System
Learn about common disorders of the muscular system by completing the learning object below.
Exercise and Muscles
Depending upon the physical activity, exercise involves a series of sustained muscle contractions.
It has both short-term and long-term effects on muscles.
The effects of exercise on muscles vary with the type and duration of the activity.
Aerobic exercises typically involve endurance and sustained muscle contractions. These exercises rely mainly on Type I (slow-twitch muscles) which sustain maximal contraction for extensive periods of time.
The availability of oxygen during aerobic exercise along with the use of Type II muscle fibers prevents the production of lactic acid due to anaerobic respiration.
Lactic acid can cause muscle soreness and indirectly causes muscle fatigue.
Anaerobic exercises, such as sprinting and weight lifting, largely use Type II (fast-twitch) muscles fibers for short, high-intensity contractions.
Low oxygen intake during this type of exercise can result in lactic acid production.
Muscle hypertrophy, or the increase in muscle mass due to exercise, particularly weight training, is a noticeable long-term effect of exercise.
Exercise of specific muscles groups can often result in hypertrophy (enlarging of the muscles).
Hypertrophy does not result from an increase in muscle fibers, but rather a combination of muscle cell growth and new protein filaments being added to individual myocytes.
Review the major muscles of the body in the learning object below:
Module Review
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