Victor Forge
The human eye is surrounded by several muscles that are integral to its function and motion. These muscles control the movement of the eyeball and eyelids, and they also play a role in vision. There are two types of eye muscles: extrinsic and intrinsic. The extrinsic muscles control eye movement and position, while the intrinsic muscles control near focusing and how much light enters the eye. There are six extraocular muscles and one muscle that controls movement in the upper eyelid. The extraocular muscles are located within the orbit but are separate from the eyeball itself. They include the superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, and inferior oblique muscles. These muscles work together to enable the eyes to move in all directions and control eye alignment.
| Characteristics | Values |
|---|---|
| Number of muscles | 6 |
| Types of muscles | Extrinsic (extraocular) and Intrinsic |
| Function of extrinsic muscles | Control eye movement and position |
| Function of intrinsic muscles | Control near focusing and how much light enters the eye |
| Number of extrinsic muscles | 6 extraocular muscles and 1 muscle controlling upper eyelid movement |
| Types of extrinsic muscles | Recti (4) and Oblique (2) |
| Recti muscles | Superior rectus, inferior rectus, medial rectus, and lateral rectus |
| Oblique muscles | Superior oblique and inferior oblique |
| Innervation | Three cranial nerves |
| Function of recti muscles | Move the eye side to side, up and down |
| Function of oblique muscles | Control rotation of the eye |
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What You'll Learn
The six muscles that control eye movement
Our eyes are controlled by six muscles that allow them to move in various directions. These muscles are known as extraocular muscles and are located within the orbit of the eye but are extrinsic and separate from the eyeball itself. They are responsible for controlling the movements of the eyeball and the superior eyelid.
The six muscles can be divided into two groups: the four recti muscles and the two oblique muscles. The recti muscles are called superior rectus, inferior rectus, medial rectus, and lateral rectus. The word "rectus" comes from the Latin "straight," representing the direct path these muscles take from origin to attachment. The superior rectus is primarily responsible for elevation, helping us look up. The inferior rectus, on the other hand, depresses, adducts, and helps rotate the eye laterally. The medial rectus and lateral rectus, as their names suggest, are positioned medially and laterally, respectively. The lateral rectus pulls the pupil away from the midline of the body.
The two oblique muscles are the superior oblique and inferior oblique. Unlike the recti muscles, the oblique muscles do not originate from the common tendinous ring. They take an angular approach to the eyeball. The superior oblique muscle is located on the upper medial side of the eye, closer to the nose. Its primary function is to turn the eye inward. The inferior oblique muscle has a similar function, moving the eye upward when looking toward the nose.
These six muscles work together to enable the eyes to move side-to-side, up and down, and diagonally. They are essential for proper eye movement and play a crucial role in our vision, including depth perception and three-dimensional sight.
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The two types of eye muscles: extrinsic and intrinsic
The eye muscles are essential for vision and eye health. There are two types of eye muscles: extrinsic and intrinsic.
Extrinsic Eye Muscles
The extrinsic eye muscles, also called extraocular muscles, are attached to the outside of the eyeball. They are responsible for controlling eye movement and position. There are six extraocular muscles and one muscle that controls the movement of the upper eyelid. These muscles are separate from the eyeball itself but are located within the orbit of the eye. The four rectus muscles and two oblique muscles work together to move the eye from side to side, up and down, and control its rotation. The rectus muscles are called superior, inferior, medial, and lateral rectus, and the oblique muscles are called superior and inferior oblique.
Intrinsic Eye Muscles
The intrinsic eye muscles are located inside the eyeball and control near focusing and how much light enters the eye through the iris. These muscles are involuntary, unlike the extrinsic muscles, which are voluntary. The intrinsic eye muscles include the ciliary muscle, iris sphincter, and radial pupil dilator muscles.
Eye Muscle Disorders
Eye movement disorders can develop due to dysfunction of the extrinsic or intrinsic eye muscles. These disorders can be mild or severe and may require eye muscle surgery in severe cases. Eye movement disorders can also be a crucial clue to many other conditions, including some serious eye and brain issues.
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The four rectus muscles
The superior rectus muscle is located at the top of the eye, with ""superior" meaning "up" or "top". This muscle helps to elevate, abduct, and laterally rotate the eyeball. It is innervated by the oculomotor nerve (CN III), and damage to this nerve can cause paralysis of the muscle, affecting the eye's resting gaze.
The inferior rectus muscle is located at the bottom of the eye, with ""inferior" meaning "down" or "bottom". This muscle works in conjunction with the superior rectus to control the vertical movement of the eyeball.
The medial rectus muscle is located on the side of the eye closest to the nose, with "medial" meaning "middle". The lateral rectus muscle, on the other hand, is found on the side farthest from the nose, with "lateral" meaning "to the side". Together, these two muscles control the horizontal movement of the eyeball, allowing it to move from side to side.
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The two oblique muscles
The human eye is a fascinating organ that relies on several muscles to function properly. Among these muscles, the two oblique muscles, known as the superior and inferior obliques, play a crucial role in eye movement and vision.
The superior oblique muscle is unique in its structure and function. It originates from the body of the sphenoid bone and extends forward, threading through a small bony opening called the trochlea on the upper-inner side of the eye socket. This muscle works like a pulley, and its actions include depressing, abducting, and medially rotating the eyeball. A lesion on the trochlear nerve (CN IV) that innervates this muscle can lead to paralysis of the superior oblique, resulting in double vision and a head tilt away from the lesion site.
On the other hand, the inferior oblique muscle also plays a vital role in eye movement. Unlike the recti muscles, which take a straight path, the inferior oblique, along with the superior oblique, follows an angular approach to attach to the posterior surface of the sclera. This muscle is responsible for abducting the eyeball and is innervated by the abducens nerve (CN VI).
Together, the superior and inferior oblique muscles are part of the extraocular muscles, which are located within the orbit but are extrinsic to the eyeball. These muscles are responsible for controlling the movements of the eyeball and the superior eyelid. Any damage to these muscles or their innervating nerves can have significant impacts on eye movement and vision, underscoring their importance in our visual system.
It is worth noting that there are other oblique muscles in the human body, such as the abdominal external oblique and internal oblique muscles, which are involved in trunk movements, bending, and breathing. However, this query specifically focuses on the two oblique muscles surrounding the eyes and their crucial role in vision and eye health.
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The superior rectus muscle
The primary function of the superior rectus muscle is to elevate the eye. It is the only muscle capable of elevating the eye when it is in a fully abducted position. Additionally, it contributes to intorsion and adduction. The muscle fibres course obliquely at a 23-degree angle with the median plane of the eye, allowing for these contrasting movements.
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Frequently asked questions
Six muscles are involved in the control of the eyeball.
These muscles are called recti muscles and oblique muscles. There are four recti muscles: superior rectus, inferior rectus, medial rectus, and lateral rectus. There are two oblique muscles: superior oblique and inferior oblique.
The recti muscles control the movement of the eyeball from side to side, up and down, and help with rotation.
The oblique muscles also control the movement of the eyeball, but they do not originate from the common tendinous ring. They attach angularly to the eye and have separate origins.
