The superior rectus muscle is a

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

in the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such a ...

. It is one of the

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the ot ...

. It is innervated by the superior division of the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements o ...

(III). In the primary position (looking straight ahead), its primary function is

elevation The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § ...

, although it also contributes to intorsion and adduction. It is associated with a number of medical conditions, and may be weak, paralysed, overreactive, or even congenitally absent in some people.

Structure

The superior rectus muscle originates from the annulus of Zinn. It inserts into the anterosuperior surface of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. This insertion has a width of around 11 mm. It is around 8 mm from the

corneal limbus The corneal limbus (''Latin'': corneal border) is the border between the cornea and the sclera (the white of the eye). It contains stem cells in its palisades of Vogt. It may be affected by cancer or by aniridia (a developmental problem), among o ...

Nerve supply

The superior rectus muscle is supplied by the superior division of the

(III).

Relations

The superior rectus muscle is related to the other

, particularly to the

medial rectus muscle The medial rectus muscle is a muscle in the orbit near the eye. It is one of the extraocular muscles. It originates from the common tendinous ring, and inserts into the anteromedial surface of the eye. It is supplied by the inferior division of t ...

and the

lateral rectus muscle Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

. The insertion of the superior rectus muscle is around 7.5 mm from the insertion of the medial rectus muscle, around 7.1 mm from the insertion of the lateral rectus muscle, and around 7.9 from the corneal limbus. There is an intermuscular septum between it and the lateral rectus muscle.

Variation

Variations of the superior rectus muscle is rare. It may rarely have two muscle bellies parallel to each other. More rarely, it may be congenitally absent.

Function

The superior rectus muscle

elevates Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

, adducts, and helps intort (rotate medially) the

Clinical significance

Testing

The superior rectus muscle is the only muscle that is capable of elevating the

when it is in a fully abducted position.

Exophthalmos

Much of the venous drainage of the orbit and the extraocular muscles passes close to the superior rectus muscle. Obstruction to this venous drainage can cause venous congestion in the eye, which may cause

exophthalmos Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen in ...

(bulging eye ball). This may be shown with CT scans.

Weakness and paralysis

The superior rectus muscle may be weakened or paralysed by problems with nerve conduction of the

(III). This may be

congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities c ...

, often with a familial genetic link, or acquired, most often caused by head injuries.

Overreaction

Local anaesthetics used in

cataract surgery Cataract surgery, also called lens replacement surgery, is the removal of the natural lens of the eye (also called "crystalline lens") that has developed an opacification, which is referred to as a cataract, and its replacement with an intraocul ...

may weaken the

inferior rectus muscle The inferior rectus muscle is a muscle in the orbit near the eye. It is one of the four recti muscles in the group of extraocular muscles. It originates from the common tendinous ring, and inserts into the anteroinferior surface of the eye. It d ...

, despite efforts to use minimal anaesthetic and to avoid placing the needle into the muscle. Weakness of the inferior rectus muscle may strengthen the superior rectus muscle, causing it to be overreactive. This may elevate the eye, and prevent its use in normal vision. Treatment may involve

eye surgery Eye surgery, also known as ophthalmic or ocular surgery, is surgery performed on the eye or its adnexa, by an ophthalmologist or sometimes, an optometrist. Eye surgery is synonymous with ophthalmology. The eye is a very fragile organ, and requ ...

that weakens or repositions the superior rectus muscle, which generally has good outcomes.

Absence

Very rarely, the superior rectus muscle may be congenitally absent. This may be caused by Apert syndrome. This causes a reduced ability to elevate the eye. It may be treated with

that uses parts of the

and the

to restore the functions normally performed by the superior rectus muscle.

Additional images

File:Gray891.png, The right eye in sagittal section, showing the fascia bulbi (semidiagrammatic). File:Trochlear and frontal nerves.jpg, Superior rectus muscle File:Slide2uu.JPG, Superior rectus muscle File:Slide1abaa.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide2abaa.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide3abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide4abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide5abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide6abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide7abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide8ababa.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection.

References

External links

* * {{Authority control Muscles of the head and neck Human eye anatomy de:Augenmuskeln#Musculus rectus superior