Skeletal Muscle Series Part 1:

Skeletal Muscles of the Head

What are skeletal muscles?

There are three types of muscles in your body – cardiac, smooth, and skeletal muscles. Cardiac muscles are found in your heart, while smooth muscles line the walls of your blood vessels, bladder, uterus, gastrointestinal tract, and other hollow internal organs. The third type, skeletal muscles, are attached to your bones and are responsible for their movements (skeletal movements).

The exact number of skeletal muscles is difficult to determine. Some muscles are present in some people but lacking or absent in others. Most of the time, it’s generally agreed upon that there are more than 650 individual skeletal muscles in the human body. The large majority of skeletal muscles come in pairs and are distributed equally on both sides of the body. When viewed under the microscope, the muscle fibres in a skeletal muscle have a striated or striped appearance. As well as being controlled voluntarily, they are also subconsciously controlled, like when you’re maintaining balance or posture.

Before we begin our journey into the complex but wonderful world of skeletal muscles, it’s essential to note that different medical specialties and health experts group skeletal muscles differently. The groupings vary regarding which muscle or muscles belong to a particular group based on function, origin (embryologic), or region of the human body. In this article series, we’ll keep it straightforward using the areas of your body to group them, namely:

Skeletal muscles found in the:

Head – Part 1
Neck – Part 2
Torso – includes muscles in the chest, back, abdomen, pelvis, and perineum – Part 3
Shoulders and upper limbs – Part 4
Lower limbs – Part 5

Skeletal Muscles of the Head

The skeletal muscles found in your head can be conveniently divided into smaller groups comprised of the following:

Muscles for facial expression. Humans have highly developed muscles in the face that allow a wide variety of facial expressions. These muscles are an essential means of nonverbal communication, exhibiting happiness, surprise, fear, anger, and other emotions. Also, they’re the only group of muscles that insert into your skin. When they contract, they also pull on the skin producing their effect as a unit. Muscles for facial expression and muscles of mastication, when grouped together, are referred to as facial muscles.
Muscles for mastication. Chewing or mastication includes four pairs of muscles. All of them attach to your mandible (jawbone). They’re recognised as some of the strongest muscles in your body.
Others. Smaller groups of muscles that move your tongue, eyes, and ears. Muscles found in your oral cavity, including the soft palate, pharynx, and larynx (voice box), are also included here.

Clinical Significance of a Few Selected Skeletal Muscles of the Head

Clinical significance is the noticeable and practical importance of an effect (disease or injury). In this case, it describes the consequences when a muscle or a group of muscles don’t perform their function well. It also characterises what happens to a muscle when it gets sick or becomes affected by a particular disease.

Bell’s palsy is a medical condition in which half (left or right) of your face appears to droop, while the opposite side is normal. It’s caused by a malfunction or defect of the facial nerve that controls the muscles for facial expression. This results in difficulty smiling, blinking, closing the eyelid and squinting on one side. While the exact cause is unknown, treatment includes drugs and physiotherapy to activate the nerve.
Trigeminal neuralgia is the feeling of too much pain on your face from a mild touch sensation (stimulus), like brushing your teeth. The pain is described as being like an electric shock, and the facial expression muscles twitch and exhibit muscle spasms.
Temporomandibular joint dysfunction may be likened to a tug of war scenario between your muscles of mastication. There is an imbalance of forces within the muscles which can be secondary to bruxism (grinding of teeth at night). Psychotherapy and biofeedback are treatment options that may help some people afflicted with temporomandibular joint dysfunction.

Skeletal muscles enable us to move and perform our daily activities. They help maintain our posture and balance. They protect vital organs in our bodies and play a crucial role in breathing. The head region contains a wide variety of skeletal muscles in all shapes and sizes. Sometimes, we take them for granted because we don’t notice them daily. It’s pretty funny because we see some of them every day when we look in the mirror to check on our faces. They’re just covered by a more conspicuous body part, our skin. If you think they’re not that important, just close your eyes and imagine if they’re affected by a disease or injured. Oh wait, you can’t close your eyes. There you go.

Check out these articles for the other skeletal muscles in your body:

Skeletal Muscles in the Neck – Part 2
Skeletal Muscles in the Torso – Part 3
Skeletal Muscles in the Shoulders and Upper Limbs – Part 4
Skeletal Muscles in the Lower Limbs – Part 5

The tables below provide a comprehensive* list of muscles found in the head region. Please note: the word muscle is removed from the actual muscle names.
*Comprehensive, but not inclusive of all the skeletal muscles found in the head region.

MUSCLES OF FACIAL EXPRESSION
Muscle	Action/Function
Orbicularis oculi Corrugator supercilii	Close the eyelid.
Nasalis Procerus Depressor septi nasi (not shown in the picture below)	Move the nose.
Orbicularis oris Buccinator Zygomaticus	These muscles are responsible for the movement of the lips and mouth, like whistling, singing, and adding emphasis while communicating.
Frontalis	Elevates the eyebrow. Shows the wrinkles on the forehead.
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MUSCLES OF MASTICATION
Muscle	Action/Function
Masseter Temporalis Medial pterygoid	Elevates the jawbone, thereby closing the mouth.
Lateral pterygoid	Allows side to side and forward movement of the jaw.
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EXTRAOCULAR MUSCLES
Muscle	Action/Function
Levator palpebrae superioris Superior tarsal	Raises upper eyelid.
Rectus muscles – superior, inferior, medial, and lateral Oblique muscles – superior and inferior	Move eyeballs in a variety of directions.
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TONGUE MUSCLES
Muscle	Action/Function
Extrinsic tongue muscles Genioglossus Hyoglossus Styloglossus Palatoglossus	Protrude, retract, elevate, depress, and roll the tongue.
Intrinsic tongue muscles Superior longitudinal Inferior longitudinal Transverse Vertical	Change the shape and size of the tongue. Facilitates speaking, eating, and swallowing.
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EAR MUSCLES
Muscle	Action/Function
Middle ear muscles Stapedius Tensor tympani	The stapedius muscle is the tiniest skeletal muscle in the body. It’s just over a millimetre in length, and its primary purpose is to stabilise the smallest bone in the body, the stapes. Cute couple, huh? The tensor tympani dampens the noise you hear or perceive from chewing your food.
External ear muscles Auricularis anterior Auricularis superior Auricularis posterior	Move the external ear forward, upward, and backward.
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SOFT PALATE MUSCLES
Muscle	Action/Function
Tensor veli palatini	Controls the tension of the soft palate.
Musculus uvulae	Changes the shape and moves the uvula.
Palatoglossus (may also be considered as a part of the extrinsic muscles of the tongue).	Raises the back part of the tongue to help in breathing.
Palatopharyngeus	Pulls the throat and voice box to help in breathing.
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MUSCLES OF THE LARYNX (VOICE BOX)
Muscle	Action/Function
Extrinsic or external laryngeal muscles Suprahyoid Infrahyoid Stylopharyngeus (may also be a part of the pharyngeal muscles)	Move the voice box upwards and downwards during swallowing.
Intrinsic or internal laryngeal muscles Cricothyroid Thyroarytenoid Posterior cricoarytenoid Lateral cricoarytenoid Transverse arytenoid Oblique arytenoid	Move individual parts of the voice box like controlling the tension and length of the vocal cords.
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MUSCLES OF THE PHARYNX*
Muscle	Action/Function
Circular muscles Superior pharyngeal constrictor Middle pharyngeal constrictor Inferior pharyngeal constrictor	These muscles contract one after the other (sequentially) from superior to inferior, narrowing the pharynx to push the food downwards to the oesophagus.
Longitudinal muscles Stylopharyngeus Palatopharyngeus (may also be a part of the palatal muscles) Salpingopharyngeus	These muscles shorten and widen the pharynx. They also elevate the voice box when swallowing.
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*The pharynx is a part of your digestive system located at the back of your nasal cavity, oral cavity, and larynx. It’s bordered by a group of muscles called the pharyngeal muscles and is divided into three parts: nasopharynx, oropharynx, and laryngopharynx.