9.4: Axial Muscles of the Head, Neck, and Back
- Page ID
- 63429
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Identify the major axial muscles of the face, head, neck, and vertebral column
- Identify the movement caused by these muscles
The skeletal muscles are divided into axial (muscles of the trunk and head) and appendicular (muscles of the arms and legs) categories. This system reflects the bones of the skeleton system, which are also arranged in this manner. The axial muscles are grouped based on location, function, or both. Some of the axial muscles may seem to blur the boundaries because they cross over to the appendicular skeleton. The first grouping of the axial muscles you will review includes the muscles of the head and neck, including those involving eye movements and swallowing, then you will review the muscles of the vertebral column.
Muscles That Create Facial Expression
The origins of the muscles of facial expression are on the surface of the skull (remember, the origin of a muscle does not move). The insertions of these muscles have fibers intertwined with connective tissue and the dermis of the skin. Because the muscles insert in the skin rather than on bone, when they contract, the skin moves to create facial expression (Figure \(\PageIndex{1}\)).
Forehead and Orbit
The occipitofrontalis muscle moves the skin of the scalp and eyebrows in a superior direction. The muscle has a frontal belly and an occipital belly located near the respective bones. In other words, there is a muscle on the forehead (frontalis) and one on the back of the head (occipitalis), but there is no muscle across the top of the head. Instead, the two bellies are connected by a broad tendon called the epicranial aponeurosis, or galea aponeurosis (galea = “apple”). The physicians originally studying human anatomy thought the skull looked like an apple. This muscle is the prime mover of the eyebrows. Gently place your finger on your eyebrows then raise your eyebrows as if you were surprised and allow them to come back to rest. With these movements, you can feel the action of the occipitofrontalis. If you watch yourself in a mirror you will see that your forehead is wrinkling as the skin moves.
The orbicularis oculi is a circular muscle that surrounds the orbit. When this muscle contracts the eyelid closes. Pretend that a bug just flew into your eye - you will close the eyelid quickly and scrunch the skin around your eye socket using your orbicularis oculi. Want to close your eyelid gently, as if peacefully sleeping? This is caused by the relaxation of another muscle - the levator palpebrae superioris. When this muscle contracts is pulls your upper eyelid open, so relaxing it allows the eyelid to close.
Nose, Mouth and Cheeks
The mouth is used for both a variety of facial expressions as well as forming words while speaking and assisting in swallowing, so it has multiple muscles inserting into the surrounding skin. The largest of these muscles is the orbicularis oris, whose fibers encircle the lips and can keep them tightly closed. Contracting the orbicularis oris when pulling in more from the corners will produce a puckered, kissing, expression. Two primary muscles pull the skin and lips in an inferior direction - depressor labii inferioris pulls the lip down while depressor anguli oris pulls the corners of the mouth down and slightly laterally creating a frowning expression. Three primary muscles pull the skin and lips in a superior direction - the levator labii superioris pulls your lip upwards toward your nose while the zygomaticus major and minor pull the corners of the mouth up and lateral to cause you to smile. If you practice contracting the zygomaticus muscles you will get the perfect, on the spot smile for pictures!
Your nose itself does not move much, but you can flare your nostrils and compress the nasal cartilage using the nasalis muscle.
The largest muscle of the cheeks is the buccinator muscle, which compresses the cheek and allows you to whistle, blow, and suck. It also contributes to the actions of chewing and swallowing. Additional muscles of facial expression are presented in Table \(\PageIndex{1}\).
| Muscle | Origin | Insertion | Movement |
|---|---|---|---|
| Brow | |||
| Occipitofrontalis (frontal belly/frontalis) | Epicranial aponeurosis | Skin of eyebrow | Furrowing (wrinkling) brow |
| Occipitofrontalis (occipital belly/occipitalis) | Occipital bone; mastoid process (temporal bone) | Epicranial aponeurosis | Retracts scalp |
| Orbit and Eyelid | |||
| Orbicularis oculi | Medial wall of orbit | Skin surrounding eyelids | Closes eyelids (blinking, squinting, winking) |
| Levator palpebrae superioris | Sphenoid bone | Skin of superior eyelid | Elevates superior eyelid |
| Nose | |||
| Nasalis | Maxilla | Skin of nostrils, nasal aponeurosis | Flaring nostrils |
| Mouth and Cheeks | |||
| Buccinator | Maxilla, mandible | Orbicularis oris | Lateral movement of cheeks (e.g. sucking on a straw; also used to compress air in mouth while blowing) |
| Depressor anguli oris | Mandible | Skin at corners of mouth | Draws corners of mouth inferior and lateral (e.g. frowning) |
| Depressor labii inferioris | Mandible | Skin of lower lip | Lowering lower lip |
| Levator labii superioris | Maxilla | Skin of the of upper lip; orbicularis oris | Raising upper lip |
| Mentalis | Mandible | Skin of chin | Protrusion of lower lip (e.g. pouting expression) |
| Orbicularis oris | Maxilla, mandible; fibers of other facial muscles | Skin surrounding lips | Compresses and purses lips (e.g. kiss) |
| Zygomaticus major and minor | Zygomatic bone | Skin at superolateral corners of mouth and lip | Smiling |
Muscles That Move the Eyes
The movement of the eyeball is under the control of the extrinsic eye muscles (extraocular muscles) that originate within the orbit and insert onto the superficial surface of the white of the eye. These muscles are located inside the eye socket and cannot be seen on any part of the visible eyeball (Figure \(\PageIndex{2}\) and Table \(\PageIndex{2}\)). If you have ever been to a doctor who held up a finger and asked you to follow it up, down, and to both sides, he or she is checking to make sure your eye muscles are acting in a coordinated pattern.
Each of these six muscles are named for their position relative to the eyeball and the orientation of their myofibers:
- Superior oblique muscle - passes through fibrous trochlea, which is attached to the superiomedial aspect of the orbit
- Inferior oblique muscle
- Superior rectus muscle
- Inferior rectus muscle
- Medial rectus muscle
- Lateral rectus muscle
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Inferior oblique | Floor of orbit (maxilla) | Surface of eyeball between inferior rectus and lateral rectus | Moves eyes up and away from nose; rotates eyeball from 12 o'clock to 9 o'clock |  |
| Inferior rectus | Common tendinous ring (ring attaches to optic foramen) | Inferior surface of eyeball | Moves eyes down and toward nose; rotates eyes from 6 o'clock to 3 o'clock |  |
| Lateral rectus | Common tendinous ring (ring attaches to optic foramen) | Lateral surface of eyeball | Moves eyes away from nose |  |
| Medial rectus | Common tendinous ring (ring attaches to optic foramen) | Medial surface of eyeball | Moves eyes toward nose |  |
| Superior oblique | Sphenoid bone | Surface of eyeball between superior rectus and lateral rectus | Moves eyes down and away from nose; rotates eyeball from 6 o'clock to 9 o'clock |  |
| Superior rectus | Common tendinous ring (ring attaches to optic foramen) | Superior surface of eyeball | Moves eyes up and toward nose; rotates eyes from 1 o'clock to 3 o'clock |  |
Muscles That Move the Lower Jaw at the Temporomandibular Joint
In anatomical terminology, chewing is called mastication. Muscles involved in chewing must be able to exert enough pressure to bite through and then chew food before it is swallowed (Figure \(\PageIndex{3}\) and Table \(\PageIndex{3}\)). The masseter muscle is the main muscle used for chewing because it elevates the mandible (lower jaw) to close the mouth, and it is assisted by the temporalis muscle, which retracts the mandible. You can feel the temporalis move by putting your fingers to your temple as you chew.
| Muscle | Origin | Insertion | Movement |
|---|---|---|---|
| Masseter | Zygomatic arch | Mandible, coronoid process and lateral surface | Closes mouth; elevation of mandible |
| Temporalis | Temporal bone | Mandible, coronoid process | Closes mouth; elevation and retraction of mandible |
Muscles That Move the Tongue
Although the tongue is obviously important for tasting food, it is also necessary for mastication, deglutition (swallowing), and speech (Figure \(\PageIndex{4}\) and Table \(\PageIndex{4}\)). Because it is so moveable, the tongue facilitates complex speech patterns and sounds.
| Muscle | Origin | Insertion | Movement |
|---|---|---|---|
| Tongue | |||
| Genioglossus | Mandible | Tongue undersurface; hyoid bone | Moves tongue down; sticks tongue out of mouth |
| Hyoglossus | Hyoid Bone | Sides of tongue | Flattens tongue |
| Styloglossus | Styloid process of temporal bone | Tongue undersurface and sides | Moves tongue up; retracts tongue back into mouth |
| Swallowing and Speaking | |||
| Digastric | Mandible; temporal bone | Hyoid bone | Raises hyoid bone in a way that also raises the larynx, allowing the epiglottis to cover the glottis during deglutition; also assists in opening the mouth by depressing the mandible |
| Mylohyoid | Mandible | Hyoid bone; median raphe | Raises hyoid bone in a way that presses the tongue against the roof of the mouth, pushing food back into the pharynx during deglutition |
| Sternohyoid | Clavicle | Hyoid bone | Depresses the hyoid bone during swallowing and speaking |
Tongue muscles can be extrinsic or intrinsic. Extrinsic tongue muscles insert into the tongue from outside origins, and the intrinsic tongue muscles insert into the tongue from origins within it. The extrinsic muscles move the whole tongue in different directions, whereas the intrinsic muscles allow the tongue to change its shape (such as, curling the tongue in a loop or flattening it).
The extrinsic muscles all include the word root glossus (glossus = “tongue”), and the muscle names are derived from where the muscle originates. The genioglossus (genio = “chin”) originates on the mandible and allows the tongue to move downward and forward. The styloglossus originates on the styloid bone, and allows upward and backward motion. The hyoglossus originates on the hyoid bone to move the tongue downward and flatten it.
Anesthesia and the Tongue Muscles
Before surgery, a patient must be made ready for general anesthesia. The normal homeostatic controls of the body are put “on hold” so that the patient can be prepped for surgery. Control of respiration must be switched from the patient’s homeostatic control to the control of the anesthesiologist. The drugs used for anesthesia relax a majority of the body’s muscles.
Among the muscles affected during general anesthesia are those that are necessary for breathing and moving the tongue. Under anesthesia, the tongue can relax and partially or fully block the airway, and the muscles of respiration may not move the diaphragm or chest wall. To avoid possible complications, the safest procedure to use on a patient is called endotracheal intubation. Placing a tube into the trachea allows the doctors to maintain a patient’s (open) airway to the lungs and seal the airway off from the oropharynx. Post-surgery, the anesthesiologist gradually changes the mixture of the gases that keep the patient unconscious, and when the muscles of respiration begin to function, the tube is removed. It still takes about 30 minutes for a patient to wake up, and for breathing muscles to regain control of respiration. After surgery, most people have a sore or scratchy throat for a few days.
Muscles of Swallowing and Speaking
The muscles of the anterior neck assist in deglutition (swallowing) and speech by controlling the positions of the larynx (voice box), and the hyoid bone, a horseshoe-shaped bone that functions as a solid foundation on which the tongue can move. The muscles of the neck are categorized according to their position relative to the hyoid bone (Figure \(\PageIndex{5}\)). Suprahyoid muscles are superior to it, and the infrahyoid muscles are located inferiorly.
A. Lateral View
B. Anterior View
C. Anterior View of Inferior ChinThe suprahyoid muscles raise the hyoid bone, the floor of the mouth, and the larynx during swallowing. Examples of these include the digastric muscle, which has anterior and posterior bellies that work to elevate the hyoid bone and larynx when one swallows; it also depresses the mandible. The mylohyoid muscle lifts the hyoid and helps press the tongue to the top of the mouth.
The strap-like infrahyoid muscles generally depress the hyoid bone and control the position of the larynx. For example, the omohyoid muscle, which has superior and inferior bellies, depresses the hyoid bone in conjunction with the sternohyoid muscles.
Muscles That Move the Head and Vertebral Column
The skull, attached to the top of the vertebral column, is balanced, moved, and rotated by muscles located in the neck. (Table \(\PageIndex{5}\)). Muscles that insert into the skull move the head at the atlanto-occipital joint and they also move the neck at the cervical intervertebral joints. Additional muscles that insert into the cervical vertebrae also cause neck movements.
When these muscles act unilaterally (on one side), the joints of the head and cervical vertebrae rotate and laterally flex. When they contract bilaterally (both right and left sides), the joints of the head and cervical vertebrae flex or extend. The major muscle that, when contracting on only one side, causes lateral flexion and rotation is the sternocleidomastoid. When both sides contract together the joints flex. Place your fingers on both sides of the neck and tilt your head to the left and to the right. You will feel the movement originate there. (Figure \(\PageIndex{6}\)).
| Muscle | Origin | Insertion | Movement | Image(s) |
|---|---|---|---|---|
| Longissimus capitis | Transverse and articular processes of cervical and thoracic vertebrae | Mastoid process of temporal bone | Rotates and tilts head to the side; tilts head backward |  |
| Semispinalis capitis | Transverse and articular processes of cervical and thoracic vertebrae | Occipital bone | Rotates and tilts head backward |  |
| Splenius capitis | Spinous process of cervical and thoracic vertebrae | Mastoid process of temporal bone; occipital bone | Rotates and tilts head to the side; tilts head backward |  |
| Sternocleidomastoid | Sternum; clavicle | Mastoid process of temporal bone; occipital bone | Rotates and tilts head to the side; tilts head forward |  |
The muscles that insert into the skull are concerned with head movements and neck movements. The neck and back muscles that insert into vertebrae both stabilize and move the vertebral column. They are grouped according to the lengths and direction of the fascicles.
The splenius muscles originate at the midline and run laterally and superiorly to their insertions. From the sides and the back of the neck, the splenius capitis inserts onto the head region, and the splenius cervicis extends onto the cervical region. These muscles can extend the head, laterally flex it, and rotate it (Figure \(\PageIndex{7}\)).
The erector spinae group forms the majority of the muscle mass of the back and it is the primary extensor of the vertebral column. It controls flexion, lateral flexion, and rotation of the vertebral column, and maintains the lumbar curve. The erector spinae comprises the iliocostalis (laterally placed) group, the longissimus (intermediately placed) group, and the spinalis (medially placed) group.
The muscles in the transversospinales group run from the transverse processes to the spinous processes of the vertebrae and they function to stabilize and move the vertebral column. Similar to the erector spinae muscles, the semispinalis muscles and multifidus muscles in this group are named for the areas of the body with which they are associated. An additional muscle, rotatores thoracis, also rotates the vertebral column. All three muscle groups extend the vertebral column.
Finally, the scalene muscles work together to flex, laterally flex, and rotate the head. They also contribute to deep inhalation. The scalene muscles include the anterior scalene muscle (anterior to the middle scalene), the middle scalene muscle (the longest, intermediate between the anterior and posterior scalenes), and the posterior scalene muscle (the smallest, posterior to the middle scalene).
3D rotation of the muscles of the head and neck.
Concept Review
Muscles are either axial muscles or appendicular depending upon the location of the joints they move. The axial muscles move joints in the axial skeleton and are grouped based on location, function, or both. Groups include:
- Facial expression: The muscles in the face create expressions by inserting into the skin rather than onto bone.
- Extraocular: Muscles that move the eyeballs are extrinsic, meaning they originate outside of the eye and insert onto it.
- Mastication: The muscles that insert into the mandible are used for chewing, with the strongest ones elevating the mandible to close the jaw. They also play a role in speaking.
- Tongue: Tongue muscles are both extrinsic and intrinsic. They create complex movements that allow the tongue to move in all three planes as well as flatten and curl. These movements are used for directing food during chewing and swallowing.
- Swallowing and speech: The muscles of the anterior neck facilitate swallowing and speech, stabilize the hyoid bone and position the larynx.
- Neck: The muscles of the neck stabilize and move the head and move the joints between the cervical vertebrae.
- Back and neck: The muscles of the back and neck move the vertebral column can be divided into multiple groups including:
- the splenius group in the posterior neck,
- the erector spinae group run the length of the vertebral column to keep up upright; this group has three subgroups: the iliocostalis group, the longissimus group and the spinalis group,
- the transversospinales group are shorter muscles that originate on the transverse processes in all regions,
- the scalenes group in the lateral neck.
Review Questions
Query \(\PageIndex{1}\)
Critical Thinking Questions
Query \(\PageIndex{2}\)
Query \(\PageIndex{3}\)
Query \(\PageIndex{4}\)
Glossary
Query \(\PageIndex{5}\)
Contributors and Attributions
OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology