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Anatomy & Physiology: Skeletal Muscle Structure and Function

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  • What surrounds a muscle fiber?
    A muscle fiber is surrounded by an extracellular matrix called endomysium.
  • What is a fascicle in muscle anatomy?
    A fascicle is a bundle of many muscle fibers enclosed by the perimysium.
  • What encloses the whole muscle?
    The whole muscle consists of many fascicles wrapped by the epimysium.
  • Name the common patterns of fascicle arrangement.
    Muscles may have parallel, convergent, pennate, circular, or spiral fascicle orientations.
  • How are some muscles named?
    Muscles are named for their shape, appearance, size, position, or number of heads (e.g., triceps).
  • What is the muscle's action?
    The muscle's action is the movement of bones at joints caused by the muscle contracting.
  • List other functions of skeletal muscle besides movement.
    Skeletal muscles also enable facial expression, breathing, and heat generation to regulate body temperature.
  • What are the points of attachment of a muscle?
    The origin is the more stationary attachment, and the insertion is the more mobile attachment.
  • How do bones and muscles work together mechanically?
    They work as lever systems to produce movement.
  • Describe a first-class lever in the body.
    A first-class lever has the fulcrum between the point of force and the load to be moved.
  • Describe a second-class lever in the body.
    A second-class lever places the load between the force and the fulcrum.
  • Describe a third-class lever in the body.
    A third-class lever places the force between the load and the fulcrum.
  • Which muscles move the forehead and eyebrows?
    The frontalis, occipitalis, and corrugator supercilii muscles.
  • What muscle closes the eye?
    The circular orbicularis oculi muscle closes the eye.
  • Which muscles produce smiling and grimacing expressions?
    The zygomaticus major, zygomaticus minor, levator labii superioris, risorius, and orbicularis oris muscles.
  • What muscles contribute to sad and doubtful facial expressions?
    The depressor anguli oris, depressor labii inferioris, and mentalis muscles.
  • Which muscle pulls the cheeks inward for sucking motions?
    The buccinator muscle.
  • Name the six extrinsic eye muscles.
    The superior, inferior, medial, lateral rectus muscles and the superior and inferior oblique muscles.
  • Which muscles are involved in mastication?
    The masseter, temporalis, medial pterygoid, and lateral pterygoid muscles.
  • Which muscles move the tongue during swallowing?
    The genioglossus, hyoglossus, and styloglossus muscles.
  • Which muscles elevate the hyoid bone during swallowing?
    The stylohyoid, mylohyoid, geniohyoid, and digastric muscles.
  • Which muscles depress the hyoid, larynx, and pharynx during swallowing?
    The sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles.
  • What is the role of the pharyngeal constrictor muscles?
    They push food into the esophagus during swallowing.
  • Which muscles move the head by rotation and flexion?
    The sternocleidomastoid and scalene muscles.
  • Which muscles extend the head?
    The trapezius, splenius capitis, and splenius cervicis muscles.
  • What muscles maintain posture and extend the vertebral column?
    The erector spinae muscle group, including iliocostalis, longissimus, and spinalis muscles.
  • Which muscles support posture and vertebral column extension in the transversospinal group?
    The semispinalis, multifidus, and rotatores muscles.
  • Which muscle extends the vertebral column laterally?
    The quadratus lumborum muscle.