Dominic Stone
The human face has about 20 muscles on each side, which are essential for chewing and making facial expressions. These muscles are typically paired, with one on the left side of the face and one on the right. Facial muscles can be divided into three main functional categories: frontal, occipital, and mimetic. The frontal belly elevates the eyebrows and skin of the forehead, creating an expression of surprise, while the occipital belly retracts the scalp. The mimetic muscles are considered extensions of the face's superficial musculoaponeurotic system (SMAS), which runs from the neck platysma to the galea aponeurotica and temporoparietal fascia under the scalp. The procerus muscle, for example, is a small pyramidal muscle between the eyebrows that depresses the medial ends of the eyebrows and wrinkles the skin in an expression of anger or disgust. Other muscles, like the nasalis muscle, compress the nasal aperture and dilate the nostrils, contributing to expressions of anger or deep breathing.
| Characteristics | Values |
|---|---|
| Number of facial muscles | 20 |
| Location of facial muscles | Face, ears, mouth, forehead, nose, eyes, neck |
| Auricular muscles | Around the ears |
| Buccolabial muscles | In and around the mouth |
| Nasalis muscle | Comprised of transverse and alar parts |
| Transverse part of nasalis muscle | Originates from the maxilla, attaches to an aponeurosis across the dorsum of the nose |
| Alar part of nasalis muscle | Originates from the maxilla overlying the lateral incisor, attaches to the alar cartilage of the nasal skeleton |
| Procerus muscle | Occupies the region between the eyebrows, arises from the nasal bone and cartilage, inserts onto the skin of the lower medial forehead |
| Occipitofrontalis muscle | Frontal part pulls the scalp forwards and wrinkles the forehead, occipital part retracts the scalp |
| Levator labii superioris muscle | Originates from the zygomatic process of maxilla and zygomatic bone, attaches to the skin and submucosa of the upper lip |
| Depressor anguli oris muscle | Arises from the oblique line and mental tubercle of mandible, attaches at the modiolus |
| Mentalis muscle | Unpaired chin muscle, permits lower lip protrusion |
| Orbicularis oris muscle | Arises from the maxilla and cheek muscles, attaches to the skin and mucous membrane of the lips |
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What You'll Learn
Muscles around the eyes and forehead
The human face has about 20 facial muscles on each side, which are essential for chewing and making facial expressions. The facial muscles are located throughout the face, including the ears, mouth, forehead, nose, and eyes. They run underneath the skin, from the scalp down to the neck.
The muscles of facial expression are unique because they originate from bones and insert into the dermis, manipulating the skin and soft tissues. They are the only group of muscles that insert into the skin. Facial muscles have a higher fast-twitch fibre concentration and fewer mitochondria than other muscles.
The procerus is a small, pyramidal muscle occupying the region between the eyebrows. It arises from the nasal bone and the superior part of the lateral nasal cartilage, extending in a fan-like manner to insert onto the skin between the eyebrows. This muscle pulls the eyebrows downward and produces wrinkles over the nose, which is associated with frowning.
The orbicularis oculi muscle surrounds the eye socket and extends into the eyelid. It has three distinct parts: palpebral, lacrimal, and orbital. It originates from the medial orbital margin, the medial palpebral ligament, and the lacrimal bone, inserting onto the skin around the margin of the orbit and the tarsal plates of the eyelid. The orbicularis oculi sphincter muscles close the eyes, depress the brows, and produce "crow's feet" wrinkles at the eyes' corners.
The corrugator supercilii is the prime mover of the eyebrows. It is the superficial muscle that depresses the eyebrows and causes "frown lines".
The six external muscles of the eyes work in pairs. When one muscle moves, its partner in the same eye helps to control and balance that movement. The superior oblique muscle works like a pulley, starting at the upper back of the eye and extending forward, then threading through a small bony opening on the upper-inner side of the eye socket, called the trochlea. After passing through the trochlea, it attaches to the top of the eyeball, just behind the superior rectus. The inferior oblique muscle attaches to the lower-inner side of the eye socket, extending laterally, wrapping around the bottom of the eye, and attaching behind the lateral rectus.
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Muscles in and around the mouth
The human face has about 20 facial muscles on each side, which are essential for chewing and making facial expressions. These muscles are located around facial openings like the mouth, eyes, nose, and ears, and extend over the skull and neck. They are typically paired, with one on the left side of the face and one on the right.
The muscles of the mouth, or buccolabial group, form a functional compound that controls the shape and movements of the mouth and lips. There are 11 of these muscles, which can be divided into upper and lower groups. The upper group contains the risorius, zygomaticus major, zygomaticus minor, levator labii superioris, levator labii superioris alaeque nasi, and levator anguli oris. The lower group contains the depressor anguli oris, depressor labii inferioris, and mentalis.
The zygomaticus major is a thin muscle that originates from the lateral surface of the zygomatic bone and extends diagonally to the angle of the mouth. It elevates the corner of the mouth and directs the corners laterally, aiding in creating a smile. The levator anguli oris also helps in smiling, while the levator labii superioris alaeque nasi can open the nostrils and lift the upper lip. The depressor anguli oris is a triangular muscle that acts to depress the angle of the mouth, contributing to expressions of sadness or anger. It also assists in opening the mouth during speaking or eating. The depressor labii inferioris helps dilate the mouth and everts the lower lip when pouting, while the mentalis is an unpaired chin muscle that permits lower lip protrusion.
The buccinator, a muscle in the buccolabial group, is a thin muscle in the cheek that holds it toward the teeth. It helps in mastication by keeping food pushed back within the oral cavity. The orbicularis oris muscle is responsible for closing the lips.
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Muscles around the ears
The muscles around the ears are a fascinating remnant of evolution. While they no longer serve a critical purpose, they still exhibit subtle movements, particularly in response to unexpected sounds. These vestigial muscles, though often overlooked, play a crucial role in ear movements and sound localisation.
The outer ear, or pinna, is composed primarily of cartilage and skin. It is attached to the skull with ligaments and muscles, and its flexible structure is maintained by elastic cartilage. The auricle, a part of the outer ear, is a musculocutaneous tissue that functions to capture sound. It is composed of intrinsic and extrinsic muscles, which are responsible for positioning the ear and forming the folds we can feel on our ears.
The three main types of extrinsic auricular muscles are the superior auricular, anterior auricular, and posterior auricular muscles. These muscles originate in the skull and attach to the auricle, pulling the ear upward, forward, and backward, respectively. The superior auricular muscle, located at the top of the ear, is the largest of the three extrinsic muscles. It moves the ear upward and outward and is considered the least active of the auricular muscles. The anterior auricular muscle, found at the front of the ear, is the smallest of the group. It is responsible for moving the ear forward and upward, and this movement can be noticeable in those who can wiggle their ears. The posterior auricular muscle, located at the back of the ear, moves the ear backward and downward.
The middle ear also contains muscles, including the tensor tympani and stapedius muscles, which attach to the ossicles of the middle ear. The tensor tympani attaches to the malleus, while the stapedius attaches to the stapes. These muscles work to decrease sound transmission through the middle ear, particularly in response to loud sounds, self-generated noise, and intense low-frequency sounds.
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Muscles around the nose
The human face has about 20 facial muscles on each side, which are essential for chewing and making facial expressions. Facial muscles are located throughout the face, including the ears, mouth, forehead, nose, and eyes. They are typically paired, with one on the left side of the face and one on the right.
The muscles around the nose are a distinct subgroup within the muscles of facial expression. One such muscle is the nasalis muscle, which compresses the nasal aperture with its transverse part and dilates the nostrils with its alar part. This action is important in creating facial expressions, such as conveying feelings of anger, and enhancing deep breathing. The nasalis muscle is also used to test the facial nerve, specifically the zygomatic branches.
Another muscle around the nose is the levator labii superioris, which originates from the zygomatic process of the maxilla and the maxillary process of the zygomatic bone. It attaches to the skin and submucosa of the upper lip, blending with other facial muscles. This muscle assists in elevating and everting the upper lip, exposing the maxillary teeth and deepening the nasolabial lines. This action is significant in making facial expressions, such as smiling, grinning, and expressing contempt.
The procerus muscle is also located in the region of the nose, between the eyebrows. It arises from the nasal bone and the superior part of the lateral nasal cartilage, extending superiorly to insert on the skin over the glabella and the medial ends of the eyebrows. This muscle depresses the medial ends of the eyebrows and wrinkles the skin over the glabella.
These muscles around the nose work in conjunction with other facial muscles to produce a range of facial expressions and enable various functions, such as deep breathing and lip movement.
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Muscles in the neck
The human face has about 20 main facial muscles that enable essential functions such as chewing and making facial expressions. These muscles are located throughout the face, including the ears, mouth, forehead, nose, and eyes. They run underneath the skin from the scalp down to the neck.
The muscles in the neck are skeletal muscles, meaning they are attached to bones by tendons. They are voluntary muscles, so you have control over their movement. There are about 30 muscles in the neck, which are divided into three main categories: anterior (front), lateral (side), and posterior (back).
The anterior neck muscles are further divided into four distinct regions: superficial, suprahyoid, infrahyoid, and scalene muscles. The superficial muscles are some of the largest in the neck. The suprahyoid muscles move the hyoid bone during swallowing and speaking. The infrahyoid muscles, which are four muscles below the hyoid bone, move the larynx up and down. The scalene muscles move the first two ribs up and down to allow for inhalation. They also help move the head and stabilize the bones in the neck (cervical spine).
The suboccipital muscles are a group of posterior neck muscles that help rotate the head and extend the neck. The rectus capitis posterior major and rectus capitis posterior minor attach the inferior nuchal line of the occiput to the C2 and C1 vertebrae, respectively. The obliquus capitis superior extends from the occiput to C1, while the obliquus capitis inferior originates from C2 and attaches to C1. The suboccipital muscles are innervated by the suboccipital nerve.
The transversospinalis, another group of posterior neck muscles, help move the head forward and backward, as well as tilt it from side to side. They also contribute to spine stabilization.
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Frequently asked questions
The human face has about 20 facial muscles that are essential for making facial expressions and chewing. These muscles are attached to the bones of the skull and the facial skin.
The procerus muscle, for instance, is a small pyramidal muscle that originates from the nasal bone and extends to insert onto the skin over the eyebrows. The occipitofrontalis, on the other hand, has a frontal part that pulls the scalp forward and wrinkles the forehead, producing a frown.
Facial muscles can be broadly categorized into two groups: the facial expression (mimetic) muscles and the mastication muscles. The mimetic muscles are further divided into three functional categories: frontal, occipital, and nasal.
