Ch. 8: Axial Muscles

Axial Muscle Functions

  • From skull to tailbone (coccyx)

  • Support and move the head and vertebral column

  • Affect facial features for nonverbal comms

  • Move the mandible during chewing

  • Assist in food processing and swallowing

  • Aid breathing

  • Support and protect abdominal and pelvic organs

Muscles of the Head and Neck

  • Almost all originate on the bones of the skull or hyoid bone

    • Muscles of facial expression

    • Extrinsic eye muscles (muscles that move your eye around)

    • Muscles of mastication (chewing)

    • Muscles that move the tongue

    • Pharynx (throat) muscles

    • Muscles that move the head and neck

Muscles of Facial Expression

  • Originate in the superficial fascia or on the skull bones

  • Insert into the superficial fascia of the skin

  • Pull on the skin, causing it to move

  • Muscle ex.

    • Occipitofrontalis (epicranius), levator labii superioris (pulls lips up), levator palpebrae superioris (pulls eyelids up), orbicularis oculi, zygomaticus major (smiling muscle), orbicularis oris, buccinator, platysma

Extrinsic Eye Muscles (Extraocular Muscles)

  • Move the eyes

  • Originate in the orbit of the skull and insert on the sclera of the eye

    • Sclera of eye = visible white portion of eye

  • Four rectus muscles (straight muscles)

    • Medial rectus

    • Lateral rectus

    • Superior rectus

    • Inferior rectus

  • Two oblique muscles

    • Superior oblique (makes eyes look downward and laterally)

    • Inferior oblique (makes eyes look upward and laterally)


Muscles of Mastication

  • Move the mandible at the temporomandibular joint (TMJ) for chewing

  • Muscle ex.

    • Temporalis

    • Masster

Muscles that Move the Tongue

  • The tongue is a highly mobile and agile muscle

  • Intrinsic muscles (inside of tongue)

    • Curl, squeeze, and fold the tongue during chewing and speaking

  • Extrinsic muscles (outside of tongue; connects to other portions of skull)

    • Have origins on head and neck structures and insert on the tongue

    • Accomplish precise mvmts for speech and food manipulation

Muscles of the Pharynx

  • Muscles help form or attach to this tube and aid in swallowing

  • Primary pharynx muscles

    • Superior, middle, and inferior pharyngeal constrictors (initiate swallowing)

  • Other pharyngeal muscles help elevate or tense the palate when swallowing

    • Tries to block food/drink from going up nasal cavity

Neck Muscles

  • Control the position of the larynx and hyoid

  • Depress the mandible

  • Control head mvmt

  • Muscle ex.

    • Sternohyoid

    • Sternocleidomastoid

Muscles of the Vertebral Column

  • Multiple origins and insertions

  • Exhibit extensive overlap

  • Maintain posture and control trunk mvmt

  • Many are covered by superficial back muscles

  • Muscle examples

    • Trapezius

    • Latissimus dorsi

Muscles of Respiration

  • During inhalation, muscles contract to enlarge the thoracic cavity and lungs

  • Exhalation typically involves muscle relaxation, but forced exhalation involves muscle contraction to forcefully dec the thoracic cavity and lung size

  • Diaphragm, external intercostals (more superficial), and internal intercostals (deeper)


  • External & internal intercostals

Diaphragm

  • Shaped like an umbrella

  • Separates the thoracic and abdominopelvic cavities

  • Most important breathing muscle

  • Muscle fibers converge from margin to a central tendon

Muscles of the Abdominal Wall

  • 4 pairs of muscles collectively compress and hold the abdominal organs in place; also flex and stabilize the vertebral column

    • External oblique

    • Internal oblique

    • Transversus abdominis

      • Deepest of the four muscles; goes L → R in a lateral position

    • Rectus abdominis

      • Note the tendinous sheaths and linea alba

      • Runs superior → inferior


      • Note transverse abdominis, tendinous sheaths, and linea alba

Muscles of the Pelvic Floor

  • The floor of the pelvic cavity is formed by three layers of muscles and associated fasciae (the pelvic diaphragm)

    • Support the pelvic cavity organs (bladder, uterus, intestines, etc.)

    • Extend from the ischium and pubis across the pelvic outlet to the sacrum and coccyx

    • Urogenital triangle

      • Contains external genitalia and urethra

    • Anal triangle

      • Contains anus