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Major Skeletal Muscles: Actions and Functions

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  • What is the primary action and function of the abductor pollicis brevis?

    Action: Abducts the thumb.
    Function: Moves the thumb away from the palm.

  • What does the adductor longus muscle do?

    Action: Adducts the thigh.
    Function: Brings the thigh toward the midline.

  • Describe the action and function of the adductor magnus.

    Action: Adducts and extends the thigh.
    Function: Stabilizes the pelvis during walking.

  • What is the role of the biceps brachii muscle?

    Action: Flexes elbow and supinates forearm.
    Function: Lifts forearm and rotates palm upward.

  • Which muscle is the main flexor of the forearm?

    Muscle: Brachialis.
    Action: Flexes elbow.
    Function: Main flexor of the forearm.

  • What is the primary function of the diaphragm?

    Action: Increases thoracic cavity volume.
    Function: Main muscle of inspiration.

  • How does the deltoid muscle contribute to arm movement?

    Action: Abducts the arm.
    Function: Main shoulder abductor.

  • What is the function of the gastrocnemius muscle?

    Action: Plantar flexes the foot and flexes the knee.
    Function: Main calf muscle for walking and running.

  • Which muscles make up the hamstrings and what are their actions?

    Muscles: Biceps femoris, semimembranosus, semitendinosus.
    Action: Flex knee and extend hip.
    Function: Aid in walking and running.

  • What is the main action of the latissimus dorsi?

    Action: Extends, adducts, and medially rotates the arm.
    Function: Main muscle for pulling movements.

  • Describe the action and function of the rectus abdominis.

    Action: Flexes the vertebral column.
    Function: Main muscle for trunk flexion.

  • What is the role of the orbicularis oris muscle?

    Action: Closes and protrudes lips.
    Function: Enables speech and kissing.

  • How do the flexor digitorum profundus and superficialis differ in action?

    Flexor digitorum profundus: Flexes distal phalanges.
    Flexor digitorum superficialis: Flexes middle phalanges.
    Both enable finger flexion.

  • What is the function of the tibialis anterior muscle?

    Action: Dorsiflexes and inverts the foot.
    Function: Raises the foot during walking.

  • Which muscle is the main extensor of the forearm?

    Muscle: Triceps brachii (medial, long, lateral heads).
    Action: Extends elbow.
    Function: Main extensor of the forearm.

  • What is the function of the external intercostals?

    Action: Elevates ribs.
    Function: Aids in inspiration.

  • How does the sartorius muscle assist in leg movement?

    Action: Flexes, abducts, and laterally rotates the thigh.
    Function: Longest muscle; aids in crossing legs.

  • What is the role of the trapezius muscle?

    Action: Elevates, retracts, and rotates scapula.
    Function: Moves and stabilizes the scapula.

  • Explain the function of the buccinator muscle.

    Action: Compresses cheek.
    Function: Aids in chewing, blowing, and sucking.

  • What is the main function of the gluteus maximus?

    Action: Extends and laterally rotates the thigh.
    Function: Main extensor of the hip.