MSM - Major Muscles and Disorders of the Muscular System Lesson

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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

The muscles of the head and neck are shown on a human head in profile:
Frontalis
Temporalis
Masseter
Trapezius
Sternocleidomas
Buccinator
Orbicularis oris
Zygomaticus
Orbicularis oculi

 

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

Muscles of the human trunk are shown: 
Pectoralis major
External oblique
Internal oblique
Rectus abdominis
Transverse abdominis

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.

The muscles of the human arm are shown: 
Deltoid
Biceps brachii
Brachioradialis
Triceps brachii

Muscles of the Lower Extremity

The muscles of the human leg are shown:
Sartorious
Rectus femoris
Vastus lateralis
Vastus medialis
Gastrocnemius
Tibialis anterior
Soleus

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.
Anaerobic exercises, such as sprinting and weight lifting, largely use Type II (fast-twitch) muscle fibers for short, high-intensity contractions.

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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