Muscle Anatomy and Properties

Muscle Definition and Properties

• Muscles are effectors that enable movement.
• Muscle tissue shortens in response to stimuli.
• Key terms include:
  • Belly: The contractile, fleshy part of a muscle.
  • Tendon: Non-contractile connective tissue attachment.
  • Aponeurosis: A flattened tendon.

Muscle Attachment Points

• Origin: Attachment to immovable or less movable bone.
• Insertion: Attachment to movable bone.
• Attachments can be through:
  • Tendon or Aponeurosis.
  • Combination of tendon and aponeurosis.
  • Direct attachment to periosteum.

Types of Muscles

Smooth Muscles

• Located in walls of viscera and blood vessels.
• Contraction is involuntary with no striations.
• Supplied by autonomic nerves.
• Cells are spindle-shaped and uni-nucleated.

Cardiac Muscles

• Found in the wall of the heart (myocardium).
• Contraction is involuntary with striations.
• Also supplied by autonomic nerves.
• Cells are uni-nucleated.

Skeletal Muscles

• Attached to the skeleton.
• Contraction is voluntary with striations present.
• Supplied by somatic nerves.
• Cells are multinucleated with multiple peripheral nuclei.

Shapes of Skeletal Muscles

• Parallel Muscles: Fibers run parallel to one another (e.g., sternocleidomastoid, rectus abdominis).

  • Variants include quadrilateral, strap, and fusiform shapes.

• Pennate Muscles: Fibers attach obliquely to a tendon.

  • Types include unipennate (e.g., extensor digitorum longus), bipennate (e.g., rectus femoris), and multipennate (e.g., deltoid).

• Triangular Muscles: Fibers converge to a narrow tendon (e.g., pectoralis major).

• Circular Muscles: Fibers arranged in circles around openings (e.g., orbicularis oris, orbicularis oculi).

Muscle Actions

• Prime Movers (Agonists): Responsible for specific movements (e.g., biceps for elbow flexion).
• Antagonists: Oppose prime movers; e.g., triceps oppose biceps during flexion.
• Synergists: Stabilize proximal joints while distal joints act (e.g., wrist muscles stabilize during finger movement).
• Fixators: Stabilize the origin of prime movers for efficient action (e.g., shoulder girdle muscles stabilize for deltoid action).
• Paradox Action: Muscles opposing gravitational movement (e.g., biceps against gravity).

Naming of Skeletal Muscles

• Based on:
  • Direction of muscle fibers (e.g., orbicularis oris).
  • Relative size (e.g., gluteus maximus, medius, minimus).
  • Location (e.g., obturator internus).
  • Number of origins (e.g., biceps, triceps).
  • Shape (e.g., deltoid).
  • Action (e.g., pronator teres).

Muscle Power Assessment

• Definition involves maximal effort from an individual muscle or group of muscles.
• Assessment method: Flexing and extending extremities against resistance.
• Tests should compare muscle power bilaterally for accuracy.

Explore the essential concepts of muscle anatomy, including definitions, attachment points, and types of muscles such as smooth, cardiac, and skeletal. This quiz will test your understanding of muscle tissue and its functions in the body.