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The human eye contains six muscles that control eye movement and eye alignment. These muscles are known as extraocular muscles and are found within the orbit of the eye but not in the eyeball itself. They are split into two groups: the recti muscles and the oblique muscles. The recti muscles are the superior rectus, inferior rectus, lateral rectus, and medial rectus. The oblique muscles are the inferior oblique and the superior oblique. These muscles are controlled by three cranial nerves: the oculomotor nerve, the trochlear nerve, and the abducens nerve.
| Characteristics | Values |
|---|---|
| Number of eye muscles | 6 |
| Types of eye muscles | Extrinsic (external) and Intrinsic (involuntary) |
| Functions of eye muscles | Control eye movement and eye alignment |
| Parts of the eye controlled by eye muscles | Superior, lateral (ear-side), and posterior (back) |
| Nerves controlling eye muscles | Cranial nerve III (oculomotor nerve), Cranial nerve IV (trochlear nerve), and Cranial nerve VI (abducens nerve) |
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What You'll Learn
The human eye has six muscles
The four recti muscles are the superior rectus, inferior rectus, lateral rectus, and medial rectus. The superior rectus is mostly in charge of elevation, helping the eye look up. The inferior rectus muscle is located at the bottom part of the eye and allows the eye to move downward. It is the only muscle that can depress the pupil when it is in a fully abducted position. The lateral rectus originates at the lateral part of the annulus of Zinn and inserts into the temporal side of the eyeball. Its main function is to pull the pupil away from the midline of the body. The medial rectus, on the other hand, brings the pupil closer to the midline. It is the largest of the extraocular muscles and its only action is the adduction of the eyeball.
The two oblique muscles are the superior oblique and inferior oblique. The superior oblique is located on the upper medial side of the eye, closer to the nose. Its primary function is to turn the eye inward, but it also contributes to other eye motions. The superior oblique muscle acts as a pulley, looping back through a connective tissue sling called the trochlea. The inferior oblique muscle inserts on the inferior, posterior, and lateral portions of the eye. Its primary function is extorsion, and its secondary functions are elevation and abduction.
These six muscles work together to move the eye from side to side, up and down, and control its rotation. They attach to the outside of the eyeball, which is why they are sometimes referred to as "external" or "extrinsic" muscles. The eye muscles are controlled by three cranial nerves: the oculomotor nerve (CN III), the trochlear nerve (CN IV), and the abducens nerve (CN VI).
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These muscles are split into two groups
The eye muscles are located in the orbit of the skull, which is the bony cavity where the eyes are situated. These muscles are essential for eye movement and work in pairs to ensure the eyes move in a coordinated manner. There are six extraocular muscles, or six external eye muscles, that control the movement of each eye. These muscles are split into two groups: the extrinsic muscles and the intrinsic muscles.
The extrinsic eye muscles are responsible for the global movement of the eye and are attached to the outer wall of the eyeball. There are four of these muscles, and they control the up-and-down and side-to-side movements of the eye. The four extrinsic muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus muscles. Each muscle has a specific role: the superior rectus pulls the eye up, the inferior rectus pulls it down, the medial rectus turns it inward, and the lateral rectus turns it outward.
The intrinsic eye muscles, on the other hand, are embedded within the eye and control fine eye movements and focusing. There are two intrinsic muscles: the ciliary muscle and the iris sphincter muscle. The ciliary muscle changes the shape of the lens, allowing the eye to focus on nearby objects—a process known as You may want to see also The human eye has six muscles that control eye movement and alignment. These muscles are known as extraocular muscles and they are responsible for all the movement of the eye. They work together to move the eye from side to side, up and down, and control its rotation. These muscles are also referred to as "external" or "extrinsic" muscles as they are located around the outside of the eyeball. The six muscles can be divided into two groups: the four recti muscles and the two oblique muscles. The recti muscles are so named because they take a direct path from origin to attachment, deriving from the Latin word "rectus" meaning "straight". The four recti muscles are the superior rectus, inferior rectus, lateral rectus, and medial rectus. The superior rectus is located at the top of the eye and helps the eye to look up, while the inferior rectus is located at the bottom of the eye and allows the eye to move downward. The lateral rectus pulls the pupil away from the midline of the body, and the medial rectus brings the pupil closer to the midline. The two oblique muscles are the superior oblique and inferior oblique. Unlike the recti muscles, the oblique muscles take an angular approach to the eyeball and have separate origins. The superior oblique is located on the upper medial side of the eye, closer to the nose, and its primary function is to turn the eye inward. The inferior oblique, on the other hand, has a primary function of extorsion and secondary functions of elevation and abduction. These eye muscles are controlled by three cranial nerves: the oculomotor nerve (CN III), the trochlear nerve (CN IV), and the abducens nerve (CN VI). The oculomotor nerve controls the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles. The trochlear nerve controls the superior oblique muscle, and the abducens nerve controls the lateral rectus muscle. You may want to see also The human eye contains six muscles that control its movement. These muscles are responsible for directing the eyes side-to-side, up and down, or at diagonal angles. These muscles attach to the outside of the eyeball and are, therefore, referred to as "external" or "extrinsic" muscles. The movement of the eye is controlled by three cranial nerves: the oculomotor nerve (CN III), the trochlear nerve (CN IV), and the abducens nerve (CN VI). These nerves carry signals to the muscles that control eye movement. The oculomotor nerve, also known as cranial nerve III, controls the movements of the superior, inferior, and medial rectus muscles, as well as the inferior oblique muscle. It is one of the three cranial nerve pairs that play a role in eye movement and is key to how the eyes move and work together. The oculomotor nerve controls several functions, including elevating the upper eyelid, rotating the eyeballs up and down, and rotating the eyeballs inward. It also enables the eyes to focus at different distances and adjusts pupil width to control the amount of light entering the eye. The trochlear nerve, or cranial nerve IV, controls the superior oblique muscle. Lesions on this nerve will paralyse the superior oblique muscle, resulting in diplopia (double vision). The abducens nerve, or cranial nerve VI, controls the lateral rectus muscle. Damage to any of these three cranial nerves will cause paralysis of the respective muscles, altering the resting gaze of the affected eye. You may want to see also Eye muscle disorders can be caused by diseases that directly weaken muscles or injuries to the eye, skull, or surrounding tissues. In the case of a skull fracture, the eye muscles can become stuck in the crack, a medical emergency known as "entrapment" that may require immediate surgery. Cranial nerve palsies are a specific type of nervous system-related muscle disorder that can affect any of the three cranial nerves that control eye movement. The sixth nerve palsy (abducens) is the most common form. Lesions on the oculomotor nerve (CN III) can cause most of the extraocular muscles to be affected, resulting in the affected eye being displaced laterally and inferiorly, a position known as "down and out." A lesion on the trochlear nerve (CN IV) will paralyse the superior oblique muscle, resulting in double vision or diplopia. Other nervous system-related disorders that can affect eye movement include myasthenia gravis, multiple sclerosis, stroke, transient ischemic attacks (TIAs), tumours and cancers of the brain or cranial nerves, nerve or brain lesions, infections such as Lyme disease, Parkinson's disease, droopy eyelid (ptosis), nystagmus (involuntary jerky eye movements), and eye misalignments such as exotropia and esotropia. Eye movement disorders can be present at birth or develop over time and may be associated with other problems, such as injuries. Two common types of eye movement disorders are strabismus, where the two eyes do not line up in the same direction, resulting in "crossed eyes" or "walleye," and nystagmus, which causes fast, uncontrollable eye movements sometimes called "dancing eyes." Treatments for eye movement disorders include glasses, patches, eye muscle exercises, and surgery, although some types have no cure, such as most kinds of nystagmus. 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