Types of Skeletal Muscles and Gross Anatomy of Muscles

• Muscles


  • Can't push—they can only pull as they contract
  • Most often body movements result from two or more muscles acting together or against each other
  • Muscles are arranged so that whatever one muscle (or group of muscles) do, other muscles can reverse
  • Groups of muscles that produce opposite movements lie on opposite sides of a joint
  • Arrangement allows muscles to bring about an immense variety of movements
• Prime mover


  Muscle that has the major responsibility for causing a particular movement
• Antagonists


  Muscles that oppose or reverse a movement
• Synergists


  Help prime movers by producing the same movement or be reducing undesirable or unnecessary movement
• Fixators


  Specialized synergists that hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone
• Head and Neck Muscles

  • Face Muscles
  • Neck Muscles
• Face Muscles


  • Frontalis
  • Orbicularis Oculi
  • Orbicularis Oris
  • Buccinator
  • Zygomaticus
  • Masseter
  • Temporalis
• Frontalis


  Covers the frontal bone, runs from the cranial aponeurosis to the skin of the eyebrows, allows you to raise your eyebrows and wrinkle your forehead
• Occipitalis


  Covers the posterior aspect of the skull and pulls the scalp posteriorly
• Orbicularis Oculi


  Fibers run in circles around the eyes, allows you to close your eyes, squint, blink, and wink
• Orbicularis Oris


  Circular muscle of the lips, often called the "kissing" muscle, closes the mouth and protrudes the lips
• Buccinator


  Runs horizontally across the cheek and inserts into the orbicularis oris, flattens the cheek (as in whistling or blowing a trumpet), also a chewing muscle
• Zygomaticus


  Extends from the corner of the mouth to the cheekbone, often referred to as the "smiling" muscle because it raises the corners of the mouth
• Masseter


  Runs from the zygomatic process of the temporal bone to the mandible, covers the angle of the lower jaw, closes the jaw by elevating the mandible
• Temporalis


  Fan-shaped muscle overlying the temporal bone, inserts into the mandible, acts as a synergist of the masseter in closing the jaw
• Neck Muscles


  • Platysma
  • Sternocleidomastoid
• Platysma


  Single sheetlike muscle that covers the anterolateral neck, originates from the connective tissue covering the chest muscles and inserts into the area around the mouth, pulls the corners of the mouth inferiorly, producing a downward sag of the mouth
• Sternocleidomastoid


  Two-headed muscle, one head arises from the sternum and the other from the clavicle, when both contract together they flex the neck, if just one contracts it rotates the face toward the shoulder on the opposite side and tilts the head to its own side
• Trunk Muscles


  • Anterior Muscles
  • Posterior Muscles
• Anterior Muscles


  • Pectoralis Major
  • Intercostal Muscles
  • Muscles of the Abdominal Girdle
  • Rectus Abdominis
  • External Oblique
  • Internal Oblique
  • Transversus Abdominis
• Pectoralis Major


  Large fan-shaped muscle covering the upper part of the chest, forms the anterior wall of the axilla, acts to adduct and flex the arm
• Intercostal Muscles


  Deep muscles found between the ribs, external intercostals help raise the rib cage when inhaling, internal intercostals depress the rib cage when exhaling forcibly
• Rectus Abdominis


  Paired straplike muscles, the most superficial muscles of the abdomen, main function is to flex the vertebral column, also compress the abdominal contents during defecation and childbirth, and are involved in forced breathing
• External Oblique


  Paired superficial muscles that make up the lateral walls of the abdomen, flex the vertebral column, rotate the trunk, and bend it laterally
• Internal Oblique


  Paired muscles deep to the external obliques, have the same functions as the external obliques
• Transversus Abdominis


  Deepest muscle of the abdominal wall, compresses the abdominal contents
• Posterior Muscles


  • Trapezius
  • Latissimus Dorsi
  • Erector Spinae
  • Quadratus Lumborum
  • Deltoid
• Trapezius


  Most superficial muscles of the posterior neck and upper trunk, extend the head, elevate, depress, adduct, and stabilize the scapula
• Latissimus Dorsi


  Large, flat muscles that cover the lower back, extend and adduct the humerus, important for bringing the arm down in a power stroke
• Erector Spinae


  Prime movers of back extension, deep muscles of the back, also provide resistance to help control bending over at the waist, go into spasms which is a common source of lower back pain
• Quadratus Lumborum


  Fleshy muscles that form part of the posterior abdominal wall, acting separately they flex the spine laterally, acting together they extend the lumbar spine
• Deltoid


  Fleshy, triangle-shaped muscles that form the rounded shape of the shoulders, prime movers of arm abduction
• Muscles of the Upper Limb

  • Muscles that arise from the shoulder girdle and cross the shoulder joint to insert into the humerus
  • Muscles that cause movement at the elbow joint
  • Muscles of the forearm
• Muscles that arise from the shoulder girdle and cross the shoulder joint to insert into the humerus

  • Pectoralis Major
  • Latissimus Dorsi
  • Deltoid
• Muscles that cause movement at the elbow joint

  • Biceps Brachii
  • Brachialis
  • Triceps Brachii
• Biceps Brachii


  Prime mover for flexion of the forearm and supination of the forearm
• Brachialis


  Lies deep to the biceps brachii, also a prime mover in elbow flexion, lifts the ulna as the biceps lifts the radius
• Triceps Brachii


  The only muscle fleshing out the posterior humerus, powerful prime mover of elbow extension, antagonist of the biceps brachii and brachialis
• Muscles of the forearm

  • Flexor carpi radialis
  • Flexor carpi ulnaris
  • Flexor digitorum superficialis
  • Extensor carpi radialis
  • Extensor digitorum
• Flexor carpi radialis


  Flexes the wrist and abducts the hand