Skeletal Muscle System

• Skeletal Muscle System is presented.

Muscle Functions

• Muscles support the body, allowing upright posture.
• They facilitate movement by attaching to the skeleton.
• Muscles help maintain a constant body temperature
• They assist in movement in the cardiovascular and lymphatic vessels.
• Muscles protect internal organs and stabilize joints.

Muscle Attachments

• Tendons are connective tissues that connect muscle to bone.
• The origin is the attachment of a muscle on a stationary bone.
• The insertion is the attachment of a muscle on a bone that moves.

Muscle Actions

• Antagonistic muscles work in opposite pairs.
• Synergistic muscles work in groups for a common action.
• Each bone is a lever and each joint is a fulcrum.
• Muscles provide the applied force to overcome resistance.

First-Class Lever

• The fulcrum is in the center, between the applied force and the resistance (seesaw).

Second-Class Lever

• The resistance is in the center, between the applied force and the fulcrum (wheelbarrow).
• A small force can move a large weight.

Third-Class Lever

• Third-class levers are the most common levers in the body.
• The applied force is in the center, between the resistance and the fulcrum.
• Requires a greater force to move a smaller resistance, but maximizes speed and distance traveled.

Muscle Names

• Muscle names relate to size, such as gluteus maximus for the largest buttock muscle.
• Names describe shape; eg deltoid is triangular (Greek letter delta is ∆).
• Location is indicated; the frontalis overlies the frontal bone.
• Direction of muscle fiber: the rectus abdominis (rectus means straight).
• Attachment: the brachioradialis is attached to the brachium and radius.
• Number of attachments: the biceps brachii has two attachments.
• Action is indicated; the extensor digitorum extends the digits.
• Muscle names include the word "muscle" except for platysma and the diaphragm.
• The word "muscle" is always implied, even when the descriptive term alone is used.

Muscle Size and Shape

• Muscle structural characteristics are indicated by the number of tendons (bi = 2, tri = 3).
• Shape: trapezius, deltoid, or rhomboid.
• or Size: longus (long), longissimus (longest), teres (long and round), brevis (short), magnus (large), major (larger), maximus (largest), minor (small), minimus (smallest).

Muscle Location and Position

• Location in the body is identified by body regions, like the temporalis muscle.
• Greek and Latin terms indicate various regions of the body.
• Examples include oris (mouth), oculi (eye), palmaris (palm of the hand), abdominis (abdomen), brachii (arm), femoris (thigh), tibialis (shin bone).
• More examples are peroneus (fibula), digitorum (finger or toe), pollicis (thumb), hallicus (great toe), costals (rib), carpi (wrist), spinalis (spine), scapularis (shoulder blade).
• Latin terms and prefixes describe position.
• Examples include supra (above or over), infra (below or beneath), sub (below or under), lateralis (the side), medialis (the middle), inter (between or among).
• More examples are external (outer), internal (inner), superior (above or over), inferior (underneath), dorsi (the back), anterior (in front of).

Direction of Muscle Fibers

• Fascicle organization describes the fascicle orientation within the muscle.
• Examples are rectus (straight), transversus, and oblique.

Muscle Origin and Insertion

• The first part of the name indicates the origin.
• The second part of the name indicates the insertion, like in Sternocleidomastoid.