Introduction to Myology

Introduction to Myology

• Myology is the study of muscle tissue and organs.

Types of Muscle Tissue

• There are three types of muscle tissue in the body:
  • Smooth muscle
  • Cardiac muscle
  • Skeletal muscle

Smooth Muscle

• Characterized by:
  • No transverse striations
  • Involuntary
  • Slow, sustained contractions with potential for great force
  • Slow to fatigue
• Examples include the walls of the stomach, intestines, and uterus.

Cardiac Muscle

• Found in the heart wall
• Difficult to fatigue
• Highly automatic
• Receives stimulation from the involuntary nervous system

Skeletal Muscle

• Composed of over 400 muscles
• Makes up about 40% of body weight
• Each muscle is composed of striated tissue, connective tissue, blood vessels, lymphatics, and nerves
• Consists of tendons and a muscle belly
• Responsible for all voluntary movements in the body (also known as "red meat")
• Muscle fibers are long and straight
• Fatigue quickly compared to other muscle types
• Controlled by the voluntary nervous system

Function of Muscles

• Supports the body
• Protects vital organs
• Allows movement
• Stores minerals
• Aids in red blood cell production
• Stores chemical energy

Origin and Insertion

• Skeletal muscles are attached to bones by tendons
• Origin: The fixed attachment; does not move; usually proximal
• Insertion: The moving attachment; moves with muscle contraction; usually distal

Characteristics of Muscle Tissue

• Excitability: Responds to nerve stimulation
• Contractility: Ability to shorten
• Extensibility: Ability to lengthen
• Elasticity: Ability to return to its original form

Muscle Names

• Muscles are named according to various criteria:
  • Location
  • Shape
  • Fiber direction
  • Action
  • Number of parts
  • Size
  • Origin and insertions

Muscle Fiber Arrangements

• Parallel Fibers:

  • Longitudinal: Fibers run in parallel lines. Example: sartorius muscle
  • Fusiform: Spindle-shaped, thicker in the middle and narrower at the ends. Example: biceps brachii
  • Quadrilateral: Four-sided muscle; fibers run parallel. Example: strap muscles

• Pennate Fibers:

  • Unipennate: Fibers insert along one side of the tendon.
  • Bipennate: Fibers insert along both sides of the tendon.
  • Multipennate: Fibers converge on multiple tendons.

• Convergent: Muscle fibers spread over a broad area, converging on a common attachment. Example: pectoralis major

• Circular: Muscle fibers arranged in a circular pattern. Example: orbicularis oris

Types of Muscle Movers

• Prime Mover: Initiates or carries out a movement. Several muscles often work together.
• Accessory/Secondary Mover: Aids in movement, especially if the load increases.
• Antagonist: Counteracts or slows down the action of the prime mover.
• Synergist/Neutralizer: Steadies a movement to eliminate undesirable movements.
• Fixator: Maintains a body part's position while another movement occurs.

Rules of Muscle Movement

• Muscle insertions move towards the origin.
• Muscles can be various types of movers depending on the action.
• More fibers in use leads to more force.

Terms to Know

• Muscle: Contracting power unit of movement.
• Tendon Sheath: Tunnel-like structure around a tendon with synovial fluid to reduce friction.
• Contraction: Main function of a muscle; causes movement by shortening and thickening of muscle fibers. Muscle fibers can shorten up to 50% of their length, and the ends contract toward the middle. Muscle always pulls, and never pushes.

Explore the fascinating world of myology, the study of muscle tissue and its types. This quiz covers smooth, cardiac, and skeletal muscle, detailing their characteristics and functions in the body. Test your knowledge on how these muscle types contribute to overall bodily functions.