STRUCTURE, COMPOSITION, AND FUNCTION OF MUSCLE TISSUE

LECTURE II

TOPIC: STRUCTURE, COMPOSITION, AND FUNCTION OF MUSCLE TISSUE

Learning Objective: To identify the components of muscle tissue and describe their structure,                                         composition & function.

There are 3 Types of muscle tissue

1. Skeletal muscle

–        Responsible for movement of skeleton (locomotion), facial expressions, posture, respiratory movements, other types of body movement

–        Under voluntary (conscious) control; controlled by somatic motor neurons

–        Appears striated under the microscope

2. Cardiac muscle

–        Responsible for movement of heart (and blood)

–        Under involuntary (unconscious) control involuntarily by endocrine and autonomic nervous systems

–        Also appears striated under the microscope

3. Smooth muscle

–        Responsible for movement of hollow organs such as digestive tract, uterus, bladder, blood vessels, skin, eye, glands

–        Also under involuntary (unconscious) control involuntarily by endocrine and autonomic nervous systems

–        Does not appear striated under the microscope

Functions & characteristics of muscle tissue

Functions:

1.      Body movement (Locomotion)

2.      Maintenance of posture

3.      Production of body heat (Thermogenesis)

4.      Stabilizing joints

5.      Respiration

–        Diaphragm and intercostal contractions

6.      Communication (Verbal and Facial)

7.      Constriction of organs and vessels

–        Peristalsis of intestinal tract

–        Vasoconstriction of blood vessels and other structures (pupils)

8.      Heart beat

Characteristics:

1. Excitability: capacity of muscle to respond to a stimulus
2. Contractility: ability of a muscle to shorten and generate pulling force
3. Extensibility: muscle can be stretched back to its original length
4. Elasticity: ability of muscle to recoil to original resting length after stretched

Connective Tissue Sheaths of skeletal muscles

Epimysium - Tough, dense connective tissue that surrounds the entire muscle (fascia).

                     -Strong, cordlike epimysia are called tendons.

                     -Sheet-like epimysium is called aponeurosis.

Perimysium - Collagen and elastic fibers surrounding a bundle of muscle fibers (fascicles).                                -Contains blood vessels and nerves

Endomysium - Loose connective tissue that surrounds individual muscle fibers

•         Also contains b.v., nerves, and satellite cells (embryonic stem cells function in repair of muscle tissue

Skeletal Muscle Attachments

• To produce movements across a joint, muscles must be attached to at least two bones.
• The origin is the attachment to the non-moving bone.
• The insertion is the attachment to the bone that moves.
• Muscles attach to origins and insertions by connective tissue

•         Fleshy attachments – connective tissue fibers are short

•         Indirect attachments – connective tissue forms a tendon or aponeurosis

• In direct attachments the epimysium of the muscle is directly attached and fused to the periosteum. Example: Temporalis, Gastrocnemius and Rectus abdominis