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The extrinsic eye muscles, also known as extraocular muscles, are the seven muscles outside the eye that govern its movements. Six of these muscles control the movement of the eye, while the seventh, the levator palpebrae superioris, controls eyelid elevation. The six muscles that control eye movement are the four rectus muscles and the two oblique muscles. The rectus muscles are the superior rectus, inferior rectus, lateral rectus, and medial rectus, and they direct the gaze upward, downward, and from side to side. The two oblique muscles are the superior oblique and inferior oblique, which work antagonistically to direct the gaze upward and downward, and also slightly rotate the eyes.
| Characteristics | Values |
|---|---|
| Number of extrinsic eye muscles | 7 |
| Number of muscles controlling eye movement | 6 |
| Names of muscles controlling eye movement | Superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, inferior oblique |
| Names of muscles controlling eyelid elevation | Levator palpebrae superioris |
| Type of movement controlled by recti muscles | Straight |
| Type of movement controlled by oblique muscles | Angular |
| Cranial nerve controlling superior oblique muscle | Trochlear nerve (CN IV) |
| Cranial nerve controlling lateral rectus muscle | Abducens nerve (CN VI) |
| Cranial nerve controlling superior rectus, inferior rectus, medial rectus, and inferior oblique muscles | Oculomotor nerve (CN III) |
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What You'll Learn
There are six extrinsic eye muscles that control eye movement
The extraocular muscles, also known as extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. Six of these muscles control the movement of the eye, while the seventh, the levator palpebrae superioris, controls eyelid elevation.
The six muscles responsible for eye movement are the four recti muscles and the superior and inferior oblique muscles. The recti muscles are named according to their relative positions of attachment: the superior rectus muscle, lateral rectus muscle, medial rectus muscle, and inferior rectus muscle. The superior rectus muscle is found at the top of the eye and controls upward movement. The medial rectus muscle attaches to the side of the eye closest to the nose and moves the eye inward. The lateral rectus muscle, meanwhile, attaches to the side of the eye closest to the temple and allows the eye to move outward.
The two oblique muscles are the inferior oblique muscle and the superior oblique muscle. The inferior oblique muscle originates at the lower front of the nasal orbital wall, passes inferiorly over the inferior rectus muscle, and inserts under the lateral rectus muscle. As a result, the inferior oblique pulls the eye upward and laterally. The superior oblique, on the other hand, travels posteriorly for the last part of its path, going over the top of the eye. When activated, it pulls the eye downward and laterally.
The actions of the six muscles responsible for eye movement depend on the position of the eye at the time of muscle contraction. Eye movements must be precise and fast, such as when reading, where the gaze must be shifted constantly. While most eye movement is accomplished without conscious effort, it is under voluntary control.
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One extrinsic eye muscle controls eyelid elevation
The extrinsic eye muscles, also known as extraocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. Six of these muscles, the four rectus muscles and the superior and inferior oblique muscles, control eye movement. The remaining extrinsic muscle, the levator palpebrae superioris, controls eyelid elevation.
The levator palpebrae superioris is responsible for raising the upper eyelid. This can be a voluntary or involuntary action. The levator palpebrae superioris is innervated by the oculomotor nerve (CN III). The superior tarsal muscle, located within the LPS, is innervated by the sympathetic nervous system.
The four rectus muscles are the superior rectus, lateral rectus, medial rectus, and inferior rectus. They are named according to their relative positions of attachment and have direct paths from origin to attachment. The two oblique muscles are the inferior oblique muscle and the superior oblique muscle. The superior oblique muscle originates at the back of the orbit and gets rounder as it courses forward. The inferior oblique muscle originates at the lower front of the nasal orbital wall and inserts under the lateral rectus muscle.
The movements of the extraocular muscles are influenced by a system of extraocular muscle pulleys, soft tissue pulleys in the orbit. The extraocular muscle pulley system is fundamental to the movement of the eye muscles and ensuring conformity to Listing's law. Four of the extraocular muscles originate in the back of the orbit in a fibrous ring called the common tendinous ring: the four recti muscles. The recti muscles are all of almost equal length of around 40 mm, but the lengths of their associated tendons differ.
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Four rectus muscles
The four rectus muscles, also known as recti muscles, are a group of four muscles that control eye movement. They are one of the two types of extraocular muscles, the other being the oblique muscles. The rectus muscles are named according to their relative positions of attachment: the superior rectus muscle, the lateral rectus muscle, the medial rectus muscle, and the inferior rectus muscle. Each eye has four rectus muscles.
The rectus muscles are all of almost equal length, at around 40 mm, but the lengths of their associated tendons differ. They attach directly to the front half of the eye, anterior to the eye's equator. The rectus muscles originate from the common tendinous ring, also known as the annular tendon or annulus of Zinn, a fibrous ring of connective tissue that surrounds the optic nerve where it connects to the orbit. The name "rectus" is derived from the Latin word for "straight", indicating that these muscles attach directly from the orbit to the sclera of the eye.
The superior rectus muscle is found at the top of the eye and controls upward movement. The medial rectus muscle attaches to the side of the eye closest to the nose and moves the eye inward. The inferior rectus muscle is located at the bottom part of the eye and allows the eye to move downward. The lateral rectus muscle is controlled by the abducens nerve (CN VI).
The movements of the rectus muscles are controlled by the oculomotor nerve (CN III). A lesion of the oculomotor nerve affects most of the extraocular muscles. The affected eye is displaced laterally by the lateral rectus and inferiorly by the superior oblique. Each rectus muscle receives blood from two anterior ciliary arteries, except for the lateral rectus muscle, which receives blood from only one.
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Two oblique muscles
The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. Six of these muscles control eye movement, while the seventh, the levator palpebrae superioris, controls eyelid elevation. The six muscles that control eye movement can be divided into two groups: the four recti muscles, and the two oblique muscles.
The two oblique muscles are the inferior oblique muscle and the superior oblique muscle. Unlike the recti group of muscles, the oblique muscles do not originate from the common tendinous ring. Instead, they take an angular approach to the eyeball, attaching to the posterior surface of the sclera.
The inferior oblique muscle originates at the lower front of the nasal orbital wall, passes inferiorly over the inferior rectus muscle on its path laterally and posteriorly, and inserts under the lateral rectus muscle on the lateral, posterior part of the globe. This means that the inferior oblique pulls the eye upward and laterally.
The superior oblique muscle, on the other hand, travels posteriorly for the last part of its path, going over the top of the eye. When activated, it pulls the eye downward and laterally. The superior oblique is controlled by the trochlear nerve (CN IV), while the inferior oblique is controlled by the oculomotor nerve (CN III).
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The levator palpebrae superioris muscle
The levator palpebrae superioris is a thin, triangular muscle that extends along the roof of the orbit, from the apex of the orbit to the superior eyelid. It originates with a short and narrow tendon from the inferior aspect of the lesser wing of the sphenoid bone, superior and anterior to the common tendinous ring. The muscle belly gradually widens as it moves anteriorly toward the eyelid, with muscle fibres penetrating the upper eyelid and attaching to its parts via two aponeurotic fascicles. Deep fibres attach to the anterior surface of the superior tarsus, while superficial fibres radiate through the eyelid and orbicularis oculi to attach to the skin of the superior eyelid.
The levator palpebrae superioris is attached to the check ligament of the superior rectus muscle, and these connections contribute to the coordinated simultaneous contraction of these two muscles. The most lateral fibres of its aponeurosis attach to the orbital tubercle of the zygomatic bone, while the most medial fibres attach to the medial palpebral ligament. The levator palpebrae superioris is a skeletal muscle, not a smooth muscle, and it has a rich blood supply provided mainly by the ophthalmic and supraorbital arteries, both emanating from the internal carotid artery.
The levator palpebrae superioris plays a role in facial expressions, as the upper lid elevation contributes to expressing feelings of fear, anger, and shock. It also has clinical significance, with levator palpebrae superioris function or innervation problems potentially resulting in upper eyelid ptosis.
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