Muscle Tissue Structure

Structure of Muscle Tissue

• Skeletal Muscle: Responsible for movement at joints and maintaining posture.
• Smooth Muscle: Responsible for movement of internal organs.
• Cardiac Muscle: Responsible for the pumping action of the heart.
• Muscle Tissue Contains:
  • Muscle Tissue
  • Nervous Tissue
  • Connective Tissue
  • Blood
• Tendon: Connects muscle to bone.
• Epimysium: A layer of connective tissue that surrounds the entire muscle.
• Fascicle: A bundle of skeletal muscle fibers.
• Perimysium: Connective tissue that surrounds each fascicle.
• Muscle Fiber: A single skeletal muscle cell.
• Endomysium: Connective tissue that surrounds each muscle fiber.
• Sarcolemma: Muscle cell membrane, located under the endomysium.
• Sarcoplasm: Cytoplasm within a muscle cell.
• Myofibril: Contractile fibers within muscle cells.
• Myofilaments: Protein filaments within myofibrils that slide past each other to produce muscle contraction:
  • Actin (Thin Filaments)
  • Myosin (Thick Filaments)
• Dark A Bands: Regions where myosin and actin filaments overlap.
• Light I Bands: Regions containing only actin filaments.
• Z Line: Holds the thin actin filaments in place.
• M Line: Holds the thick myosin filaments in place.
• H Zone: Region containing only myosin filaments.
• Sarcomere: Contractile unit of muscle; the myosin filaments pull actin filaments closer to the center (H zone).
• Important Note: During muscle contraction, the filaments do not shorten. They slide past each other.

Body Movements

• Flexion: Bending parts at a joint, decreasing the angle between them.
• Extension: Straightening parts at a joint, increasing the angle between them.
• Dorsiflexion: Movement at the ankle that brings the foot towards the shin (walking on heels).
• Plantar Flexion: Movement at the ankle that brings the foot farther from the shin (walking on toes).
• Hyperextension: Extension of parts at a joint beyond anatomical position (can lead to injury).
• Abduction: Moving a part away from the midline of the body.
• Adduction: Moving a part towards the midline of the body.
• Rotation: Moving a body part around an axis.
• Circumduction: Moving a body part so its end follows a circular path.
• Supination: Turning the hand so the palm is upward or facing anteriorly (holding a bowl of soup).
• Pronation: Turning the hand so the palm is downward or facing posteriorly.
• Eversion: Turning the foot so the plantar surface (sole) faces laterally.
• Inversion: Turning the foot so the plantar surface faces medially.
• Protraction: Moving a body part forward.
• Retraction: Moving a body part backward.
• Elevation: Raising a body part.
• Depression: Lowering a body part.

Skeletal Muscles (Intro, Roles & Naming)

• Prime Movers (Agonists): The major muscle responsible for a specific movement when several muscles are contracting.
• Synergists: Muscles that assist prime movers by reducing undesirable or unnecessary movements.
• Fixators: Specialized synergists that hold a bone still during a movement.
• Antagonists: Muscles that oppose or reverse a movement.

Naming Muscles

• Many naming conventions exist to help identify and differentiate muscles. Some include:
  • Location: (e.g., temporalis, pectoralis)
  • Size: (e.g., gluteus maximus, teres minor)
  • Shape: (e.g., deltoid, trapezius)
  • Direction of Fibers: (e.g., rectus, oblique)
  • Number of Origins: (e.g., biceps brachii, triceps brachii)
  • Action: (e.g., flexor carpi radialis, adductor magnus)
  • Points of Attachment: (e.g., sternocleidomastoid)

This quiz covers the essential components and functions of different muscle tissue types, including skeletal, smooth, and cardiac muscles. It explores the connective tissues that support muscle structure and their roles in muscle contraction and movement. Test your understanding of muscle anatomy and function!