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Plate AT-M

Muscles

Injection sites and why the others are refused, breathing muscles, reflexes, and mobility.

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TEXT ONLY — NOT A SEPARATE PART OF THIS MODEL: Masseter and temporalis · Muscles of facial expression · Abdominal wall and rectus abdominis · Pelvic floor (levator ani) · Skeletal muscle as tissue

Head and neck

4 structures

Head and neck

Masseter and temporalis

The two jaw-closing chewing muscles you can feel from outside: the masseter over the angle of the jaw and the temporalis in the temple.

Why the exam cares

The nurse tests them to check the motor part of cranial nerve V, by feeling both sides while the patient clenches. When the teeth cannot open, from a seizure or a jaw wired shut, the nurse keeps the airway clear without forcing the mouth.

How to find it

  • The masseter runs from the cheekbone (zygomatic arch) to the outer angle of the jaw; it bulges under the fingers there when the patient clenches.
  • The fan-shaped temporalis fills the side of the head at the temple; feel it tighten above and in front of the ear during the same clench.
  • The jaw joint (temporomandibular joint) sits just in front of the tragus, the small flap in front of the ear canal; feel it glide as the patient opens and closes.
  • The other two chewing muscles, the medial and lateral pterygoids, lie deep and cannot be felt from outside; they help move the jaw side to side and forward.

Nerve

Cranial nerve V motor test

The nurse rests fingers on both masseters and both temporalis muscles while the patient clenches, comparing bulk and strength side to side. A weak or wasted side points to a problem in the mandibular branch (V3), which carries all of the nerve's motor fibers. Sensation is checked separately with light touch on the forehead, cheek, and chin, comparing sides.

Assessment

TMJ assessment

With fingertips just in front of each tragus, the nurse has the patient open and close the mouth. The joint should move smoothly, and a painless click can be a normal finding. Pain, a grating feel (crepitus), locking, the jaw pulling to one side, or an opening narrower than about three fingers is documented and reported.

Emergency

Jaw wired shut

Critical

A patient whose jaws are wired together cannot open the mouth to clear vomit, so wire cutters stay at the bedside and go with the patient everywhere, and suction is kept ready. The nurse teaches the patient to turn to the side and let the mouth drain if nauseated. The wires are cut only for an airway emergency, following facility policy, because cutting them releases the fixation holding the fracture.

Emergency

Clenched teeth in a seizure

Critical

When these muscles clamp the teeth shut during a seizure, the nurse never forces a tongue blade, oral airway, or fingers between the teeth; this can break teeth, block the airway, and injure the nurse. Instead the nurse turns the patient to the side so secretions drain, protects the head, loosens tight clothing, and times the seizure.

Health Promotion and MaintenanceSafety and Infection ControlReduction of Risk Potential
Head and neckHigh yield

Muscles of facial expression

The thin muscles under the skin of the face that raise the eyebrows, close the eyes, smile, and puff the cheeks.

Why the exam cares

All of them run on cranial nerve VII, so a drooping face is the F in the FAST stroke screen, and the forehead tells the nurse whether the problem is in the brain or in the nerve. The NCLEX asks the nurse to tell a stroke from Bell palsy and to protect the eye that no longer closes.

How to find it

  • Look at the face at rest: the folds from nose to mouth corner should match and the mouth should sit level.
  • Then in motion: eyebrows up, eyes squeezed shut, big smile, cheeks puffed, each compared side to side.
  • The forehead is the dividing line: a wrinkling forehead with a drooping mouth points to the brain (the upper face has input from both sides of the cortex); a whole half-face that will not move, forehead included, points to the nerve itself, as in Bell palsy.

Nerve

Cranial nerve VII test

The nurse asks the patient to raise the eyebrows, close the eyes tightly while the nurse tries to open them, smile showing teeth, and puff out the cheeks. Any asymmetry is documented by side and by whether the forehead moved.

Emergency

Sudden facial droop

Critical

A new droop of one side of the mouth, especially with arm weakness or slurred speech, is a stroke until proven otherwise. The nurse notes the time the patient was last known well, calls the stroke alert, checks the blood glucose, keeps the patient NPO until a swallow screen, and prepares for a CT scan.

Assessment

Bell palsy

In Bell palsy the whole half of the face is limp, forehead included, because the facial nerve itself is inflamed and swollen. The eye on that side cannot blink or close, so the nurse gives artificial tears by day and lubricating ointment with an eye patch or tape at night, and teaches the patient to chew on the strong side and check the cheek for pocketed food.

Physiological AdaptationReduction of Risk Potential
Head and neckHigh yield

Sternocleidomastoid and scalenes

The neck muscles that help with hard breathing: the sternocleidomastoid runs from behind the ear to the breastbone and collarbone, and the three scalenes lie deeper in the side of the neck, running from the neck vertebrae to the first two ribs.

Why the exam cares

Quiet breathing needs only the diaphragm and the muscles between the ribs, so neck muscles pulling with each breath mean the work of breathing is high. The red flag is new or worsening use compared with the patient's baseline: a patient with long-standing COPD may use these muscles every day, while an asthma or pneumonia patient who starts using them needs to be seen first.

How to find it

  • The sternocleidomastoid stands out as a ridge from behind the ear to the notch at the top of the breastbone when the patient turns the head to the opposite side against resistance.
  • The scalenes lie behind and deep to the sternocleidomastoid, just above the collarbone.
  • The carotid pulse lies just inside the front edge of the sternocleidomastoid, level with the Adam's apple (thyroid cartilage).

Assessment

Accessory muscle use

Watch

Neck muscles cording with each breath, shoulders lifting, and leaning forward on the hands (tripod position) mean the diaphragm cannot move enough air alone; in long-standing COPD some of this can be the patient's usual pattern, so the nurse compares it with baseline. When it is new or worsening, the nurse sits the patient upright, checks oxygen saturation and respiratory rate, gives oxygen as ordered, and reports the change right away. A tiring patient's rate can slow, and that is respiratory failure beginning, not recovery.

Assessment

Supraclavicular retractions

Critical

The hollow above the collarbone sinks in on inspiration when the chest is pulling hard against a blocked airway or stiff lungs, and retractions here or above the breastbone mean more severe distress than retractions between or below the ribs. The nurse sits the patient upright, applies oxygen, stays at the bedside, and calls the provider or rapid response team without waiting for the saturation to fall. A wheezing patient whose chest goes quiet has stopped moving air; that is worse, not better.

Pulse point

Carotid pulse beside the muscle

Watch

The nurse slides two fingers into the groove between the windpipe and the front edge of the sternocleidomastoid, presses gently, and checks one side at a time. Pressing both sides at once, or rubbing the artery, can slow the heart and cut blood flow to the brain, and in an older adult can loosen plaque. During CPR the nurse checks here for no more than 10 seconds before resuming compressions.

Nerve

Cranial nerve XI head turn

The nurse tests the spinal accessory nerve by having the patient turn the head against the nurse's hand; the sternocleidomastoid opposite the direction of the turn should tighten. The nurse then has the patient shrug against resistance to test the trapezius, which the same nerve supplies. Weakness points to a problem with the nerve on the side of the weak muscle.

Physiological AdaptationReduction of Risk Potentialasthma copd →
Head and neckHigh yield

Tongue (genioglossus)

The main tongue muscle, anchored to the inside of the chin, that pulls the tongue forward and holds it off the back of the throat.

Why the exam cares

When a patient loses consciousness this muscle goes slack and the tongue falls back and blocks the airway, the most common cause of airway obstruction in an unresponsive patient. The NCLEX asks the nurse to open the airway with a head-tilt chin-lift or jaw thrust, and to test cranial nerve XII by asking the patient to stick out the tongue.

How to find it

  • Runs from the inside of the jaw at the chin back into the body of the tongue along the floor of the mouth.
  • Lifting the chin or pushing the angle of the jaw forward pulls this attachment forward and lifts the tongue off the throat.
  • Snoring in an unresponsive patient is the sound of the slack tongue partly blocking the airway and calls for repositioning; gurgling means fluid in the airway and calls for suction.

Emergency

Tongue blocking the airway

Critical

In an unresponsive patient with snoring breaths or no air movement, the nurse tilts the head back and lifts the chin; if a neck injury is possible, the nurse uses a jaw thrust instead, pushing the angles of the jaw forward without moving the neck. An oral airway holds the tongue forward in a patient with no gag reflex.

Nerve

Cranial nerve XII test

The nurse asks the patient to stick the tongue straight out and move it side to side. A tongue that drifts toward one side is weak on that side; the nurse documents the direction and watches for trouble swallowing and speaking.

Assessment

Recovery position after seizure or sedation

A drowsy or post-seizure patient is turned onto the side so gravity pulls the tongue forward and secretions drain out of the mouth instead of down the throat. The nurse keeps suction at the bedside and does not leave the patient flat on the back.

Physiological AdaptationSafety and Infection Control

Sources

SourceLicense
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 InternationalThe 3D plates. Modified: element meshes merged per structure, simplified, compressed, and recoloured for the web.CC-BY-4.0
OpenStax Anatomy and Physiology 2e (CC BY 4.0)Informed the anatomical facts. The prose is original to this portal.CC-BY-4.0
MedlinePlus / NIHPublic Domain (US Gov)
Nursing Nerds editorialEvery sentence in the atlas entries, each passed through independent clinical review.Original