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
- 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
- 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
- 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
1. Body movement (Locomotion)
2. Maintenance of posture
3. Production of body heat (Thermogenesis)
4. Stabilizing joints
– 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
- Excitability: capacity of muscle to respond to a stimulus
- Contractility: ability of a muscle to shorten and generate pulling force
- Extensibility: muscle can be stretched back to its original length
- 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