muscles

Basic Anatomical Structures Skeletal muscles Dr : Hassna Bader

Wednesday 9/12/2015 Page 1

The skeletal muscles

Objective:
Define the muscle
List the function of the muscles.
Describe the skeletal muscle and its classification.
Nomenclature and organization of skeletal muscle.
Define ligament and tendon.
Muscle comes from Latin word ( MUS) which means small mouse Muscle is Specialized tissue that enable the body and its parts to move. About 640 Muscles make up about 40 % of the body mass.
Function of the muscle
• 1.Production of Movement.
• 2.Maintenance of posture and tone.
• 3.Heat production by thermo genesis.
• 4.Protects the bones and internal organs .
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Skeletal muscle
Composed of striated muscle cells (muscle fibers) and connective tissue. Each muscle consist of 3 parts :
1. The Origin : the attachment to the bone that does not move .
2. The belly: is the fleshy part of the muscle between the tendons of origin and insertion
3. The insertion: the attachment to the bone that moves
Tendons or aponeurosisThe muscles anchor firmly to bones by
Nomenclature of the muscle:
• 1.Number of origins – e.g., biceps (two origins) and triceps (three origins)
• 2.Location of attachments – named according to point of origin or insertion e.g. coracobrachialis
• 3.Action: e.g., flexor or extensor, adductor, abductor as flexor digitorum or adductor magnus.
• 4.Location of muscle – bone or body region associated with the muscle e.g. Brachialis
• 5.Shape of muscle – e.g., the deltoid muscle or trapezius
• 6.Relative size – e.g., medius ,minimus (smallest), longus (long) as gluteus medius
• 7.Direction of fibers – e.g., rectus (fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis) as rectus abdominus muscle

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Basic Anatomical Structures Skeletal muscles Dr : Hassna Bader
Wednesday 9/12/2015 Page 2

Classification of the muscles:

• 1. Prime movers – Chief muscle which provides the major force for producing a specific movement e.g. quadraceps femoris muscle in extending the knee.
• 2. Antagonists – opposes the action of prime movers e.g Biceps femoris opposes the action of quadraceps femoris.


3. Synergists:
The muscle contracts to assist the prime mover in performing that action. e.g. supraspinatous muscle assists deltoid in abduction.
• 4.Fixators :
• A synergists muscle that immobilize a bone or muscle’s origin .it only increase the tone to stabilize the joint e.g. muscles around the shoulder joint ( rotator cuff muscles ) .
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• Organization of skeletal muscle

Muscle cells (fibers) are organized in bundles (fascicles) .Fibers in fascicle arranged in 4 different shapes with respect to tendon :
• 1.Parallel muscle
• Fascicles run parallel to length of the muscle. Most skeletal muscles are arranged this way
• The length of the muscle is changed and can move load over a great distance e.g. biceps muscle.
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• 2.Convergent muscle:
• Fascicles spread out like a fan on one end and converge to a single point on the other
• Produce less tension and distance than parallel muscles . Muscle fibers pull in different directions .e.g. Pectoralis major muscle
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• 3.Pennate muscle:
• Fascicles are arranged at an angle to tendon:

A. Unipennate: Fascicle angled on one side of tendon

B. Bipennate: Tendon in middle with angled fascicles on either side
C. Multipennate: Branched tendon with fascicles organized around each branch
**Pennate muscles produce more tension than parallel muscles but cannot move so far, less distance
produced.
• 4. Circular muscle:
• Concentric arrangement of fascicles. Also called sphincters. It Decrease diameter of openings to guard entrances and exits
• e.g., obicularis oris
Basic Anatomical Structures Skeletal muscles Dr : Hassna Bader
Wednesday 9/12/2015 Page 3


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The Ligament :

Ligament means binding together. It is connective tissue consist of collagen and elastic fibers
2 types of ligament :
1.Visceral ligament:
which connects viscera to one another or to the body wall e.g. ligament between liver and diaphragm
2.Skeletal ligament :
Band of connective tissue connects two bones and blends with the fibrous wall of joint cavity.
*with stand pull at the joint they cross.
• *Most consists of collagen fiber and therefore allow stretch.
• *Some consists elastic fiber as in ligamentum flavium of vertebral column.

The Tendon :

Tissue attaches the skeletal muscle to other structures. Its proximal end attaches to the muscle and its distal end blends with the periosteum of the bone .
*It is broad and flat when they are a part from flat muscle and corde like when it is a part of long slender muscle.
*Very broad flat tendon are known aponeurosis
• The Bursa
• *Closed connective tissue sac close to the joint synovial joints , filled with fluid and slippery inner surface.
• * presents between tendon & bone, Ligament & bone , muscle & bone and skin & bone.
• It acts to prevent friction between these structures during movement of the adjacent joint.
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