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The extrinsic eye muscles, also known as extraocular muscles, are the seven muscles that control eye movement and position in humans and other animals. Six of these muscles, the four recti muscles and the superior and inferior oblique muscles, control the movement of the eye. The seventh muscle, the levator palpebrae superioris, controls eyelid elevation. The extraocular muscles are innervated by three cranial nerves, and damage to one of these nerves will cause paralysis of its respective muscles.
| Characteristics | Values |
|---|---|
| Number of extrinsic eye muscles | 6 or 7 |
| Types of extrinsic eye muscles | Recti muscles, oblique muscles, and levator palpebrae superioris |
| Function of recti muscles | Control eye movement in different directions |
| Function of oblique muscles | Control eye movement in different directions |
| Function of levator palpebrae superioris | Controls eyelid elevation |
| Innervation of recti muscles | Cranial nerve III (oculomotor nerve) |
| Innervation of oblique muscles | Cranial nerve IV (trochlear nerve) and cranial nerve VI (abducens nerve) |
| Innervation of levator palpebrae superioris | Oculomotor nerve (CN III) |
| Blood supply to extrinsic eye muscles | Branches of the ophthalmic artery |
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What You'll Learn
- There are six extraocular muscles that control eye movement
- One muscle controls the upper eyelid
- The four recti muscles are named according to their relative positions of attachment
- The two oblique muscles are the inferior and superior oblique
- The extraocular muscles are supplied by the ophthalmic artery
There are six extraocular 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 eye movement, 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 four recti muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus. These muscles originate from the common tendinous ring, a ring of fibrous tissue that surrounds the optic canal at the back of the orbit. From their origin, the muscles pass anteriorly to attach to the sclera of the eyeball. The name "recti" is derived from the Latin for "straight", representing the direct path these muscles take from origin to attachment. The superior rectus muscle, found at the top of the eye, controls upward movement. The medial rectus, located on the side closest to the nose, moves the eye inward. The lateral rectus is responsible for abduction, moving the pupil away from the body's midline. The inferior rectus is located at the bottom part of the eye and allows the eye to move downward.
The two oblique muscles are the superior oblique and the inferior oblique. Unlike the recti muscles, the oblique muscles do not originate from the common tendinous ring. Instead, they take an angular approach to attach to the posterior surface of the sclera. The superior oblique muscle originates from the sphenoid bone, one of the bones that make up the eye socket, and is controlled by the trochlear nerve. It functions in internal rotation in a neutral gaze and intorsion when the eye is in the primary position. The inferior oblique muscle originates at the lower front of the nasal orbital wall, passing inferiorly over the inferior rectus muscle, and inserts under the lateral rectus muscle on the lateral, posterior part of the globe. This muscle pulls the eye upward and laterally.
The extraocular muscles are innervated by three cranial nerves: the oculomotor nerve (CN III), the trochlear nerve (CN IV), and the abducens nerve (CN VI). These nerves coordinate the movement of the muscles, ensuring precise and fast eye movements.
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One muscle controls the upper eyelid
The extrinsic eye muscles, or extraocular 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 the elevation of 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 levator palpebrae superioris and superior tarsal muscles both act to open the eyelid. They are only present in the upper eyelid. The palpebral conjunctiva forms the deepest layer of the eyelid. It is a thin mucous membrane, which is reflected onto the sclera of the eyeball (bulbar conjunctiva). The eyelid has a rich arterial supply from numerous vessels. Ophthalmic artery branches include the lacrimals, medial palpebral, supraorbital, dorsal nasal, and supratrochlear arteries. The facial artery and superficial temporal artery also supply the eyelid through their angular branch and transverse facial artery branch, respectively.
The orbicularis oculi muscle has three distinct parts: palpebral, lacrimal, and orbital. The superior tarsus acts as the attachment site of the levator palpebrae superioris. The superior tarsus also contains the Meibomian glands, which secrete an oily substance onto the eye to slow the evaporation of the tear film. This oily substance also prevents the eyelids from sticking together when closed.
The levator palpebrae superioris muscle, with minor contributions from Müller's and the frontalis muscles, maintains the normal position of the upper eyelid. The aponeurosis of the levator muscle attaches to the anterior surface and the superior edge of the superior tarsal plate. Both levator muscles are controlled by the central caudal nucleus (CCN) of the oculomotor nuclear complex (cranial nerve III). Within the CCN, neurons to both levators are intermixed. Müller's muscle is innervated by oculosympathetic neurons, while the frontalis receives fibers from the facial nerve.
The eyelids move with the eyes during both slow and rapid vertical eye movements, except when blinking. During blinking, the levator is temporarily inhibited and the orbicularis oculi contracts. Vertical eye movements and lid position are coordinated through the M-group (supraoculomotor area or supra III) in the midbrain. In upgaze, M-group neurons excite the CCN, causing the levator muscles to contract and the eyelids to open. During downgaze, neurons from the interstitial nucleus of Cajal (inC) inhibit the M-group neurons and the CCN, resulting in levator relaxation and eyelid lowering.
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The four recti muscles are named according to their relative positions of attachment
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 the movement of the eye, and they are the four recti muscles and the superior and inferior oblique muscles. The four recti muscles are named according to their relative positions of attachment. The four recti muscles are: the superior rectus muscle, the lateral rectus muscle, the medial rectus muscle, and the inferior rectus muscle. The names of these muscles are derived from their positions in relation to the midline, which is an imaginary line that runs down the centre of the body. The superior rectus muscle is the top muscle, with "superior" meaning "up" or "top". The inferior rectus muscle is the bottom muscle, with "inferior" meaning "down" or "bottom". The medial rectus muscle is the muscle closest to the nose, with "medial" meaning "middle". The lateral rectus muscle is the muscle farthest from the nose, with "lateral" meaning "to the side", like where the ears are.
The four recti muscles are almost equal in length, at around 40 mm, but the lengths of their associated tendons differ. They originate from the common tendinous ring, a ring of fibrous tissue that surrounds the optic canal at the back of the orbit. From their origin, the muscles pass anteriorly to attach to the sclera of the eyeball. The recti muscles are named after their straight paths from origin to attachment. The two oblique muscles, on the other hand, take an angular approach to the eyeball.
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The two oblique muscles are the inferior and superior oblique
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 control eye movement, while the seventh, the levator palpebrae superioris, controls eyelid elevation. The six muscles responsible for eye movement are the four recti muscles and the two oblique muscles.
The inferior oblique, on the other hand, 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. Thus, the inferior oblique pulls the eye upward and laterally. The thin inferior oblique muscle lies near the anterior border of the floor of the orbit. Similar to the superior oblique muscle, but unlike the recti muscles, the inferior oblique does not originate from the common tendinous ring. Instead, it arises from the anterior aspect of the orbit.
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The extraocular muscles are supplied by the ophthalmic artery
The extraocular muscles, also known as the extrinsic ocular muscles, are the seven muscles extrinsic to the eye in humans and other animals. Six of these muscles, the four recti muscles and the superior and inferior oblique muscles, are responsible for eye movement. The seventh muscle, the levator palpebrae superioris, controls eyelid elevation.
The ophthalmic artery then turns medially, giving off 1 to 5 posterior ciliary arteries, which branch into the long and short posterior ciliary arteries. These arteries pierce the sclera on the posterior aspect of the eyeball, just lateral to the optic nerve, and supply the sclera, choroid, and anterior segment of the eyeball. The long posterior ciliary arteries end near the sclerocorneal junction by joining the major arterial circle of the iris. The lacrimal artery, one of the largest branches of the ophthalmic artery, supplies the lacrimal gland, eyelids, conjunctiva, and parts of the dura mater.
The ophthalmic artery also has two terminal branches: the supratrochlear artery and the dorsal nasal artery. These arteries exit the orbit medially to supply the forehead and scalp. Occlusion of the ophthalmic artery can produce sight-threatening conditions, such as ocular ischemic syndrome, and may result from systemic cardiovascular diseases.
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Frequently asked questions
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 control eye movement, and the seventh controls eyelid elevation.
The six extrinsic eye muscles that control eye movement are the four recti muscles (superior, inferior, medial, and lateral rectus) and the two oblique muscles (superior and inferior oblique). The extrinsic eye muscle that controls eyelid elevation is the levator palpebrae superioris.
The four recti muscles are named according to their relative positions of attachment. The superior rectus muscle, for example, is found at the top of the eye and controls upward movement. The medial rectus muscle is the muscle closest to the nose and moves the eye inward. The two oblique muscles, unlike the recti muscles, do not originate from the common tendinous ring. Instead, they take an angular approach to attaching to the eyeball.
