The superior rectus and inferior oblique muscles working together pull the eye upward without rotating the eye. To depress the eye while looking straight ahead, the inferior rectus and superior oblique contract together as the superior rectus and inferior oblique relax. The extraocular muscles are located within the orbit, but are extrinsic and separate from the eyeball itself. They act to control the movements of the eyeball and the superior eyelid. There are seven extraocular muscles - the levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique. A 6-year-old boy who had been treated with bilateral medial rectus muscle recessions 3 years earlier for congenital esotropia was undergoing bilateral inferior oblique muscle recessions to correct inferior oblique muscle overaction. The right inferior rectus muscle was inadvertently cut during this surgery and was irretrievable. To manage this complication, the medial rectus.

Medial Rectus And Inferior Oblique Dmg Exercises
Medial Rectus Definition
Medial Rectus And Inferior Oblique Dmg Muscle
Medial Rectus And Inferior Oblique Dmg Muscles
Medial Rectus And Inferior Oblique Dmg
Medial Rectus Muscle Function

There is a short list of causes for enlarged extraocular muscles. The differential can be narrowed by the clinical history, known systemic illness, pattern of specific muscles involved, the muscle morphology, as well as concurrent findings outside the muscles 3: it can involve any combination of muscles, medial rectus more than lateral rectus. The medial rectus is a muscle located in the eye socket. This muscle works within a sort of pulley-system and, along with other extraocular muscles, helps to control certain movements of the eye. The role of the medial rectus in eye movement is that of adduction. That is to say, the eye moves in an inward direction, as toward the nose.

The extraocular muscles are classified into 2 groups: voluntary and involuntary.

Voluntary Muscles

There are 7 voluntary muscles in the orbit. Of those, 6 muscles move the eyeball and 1 muscle moves the upper eyelid.

The muscles moving the eyeball are 4 recti and 2 oblique muscles. The 1 which moves the upper eyelid is named levator palpebrae superioris:

4 recti muscles.
Superior rectus.
Inferior rectus.
Medial rectus,
Lateral rectus.
2 oblique muscles.
Superior oblique,
Inferior oblique.
1 levator palpebrae superioris.

Involuntary Muscles

There are only three automatic/ smooth muscles, viz. superior tarsal or Muller’s muscle, inferior tarsal and orbitalis.

Recti Muscles

Origin: All the recti originate from the corresponding margins of the common tendinous ring. The lateral rectus originates by 2 heads.

The common tendinous ring encloses the optic canal and middle part of the superior orbital fissure. It’s connected medially to apex of the orbit and laterally to a small tubercle (tubercle of Zinn) on the lower border of superior orbital fissure.

Insertion: All the recti are added into sclera little posterior to the limbus (corneoscleral junction) in front of the equator of the eyeball. Typical space from limbus is: Medial rectus, 5 millimeters Inferior rectus, 6 millimeters Lateral rectus, 7 millimeters Superior rectus, 8 millimeter

Oblique Muscles

The oblique muscles of the orbit are superior and inferior. Their origin and insertion are as follows:

Superior Oblique

Origin: from body of sphenoid superomedial to the optic canal.

Insertion: into sclera supporting the equator in posterior superior quadrant of the eyeball, between the superior rectus and lateral rectus. The tendon of superior oblique goes through a fibrocartilaginous pulley connected to the trochlear notch in the anterolateral part of the roof of the orbit.

Inferior Oblique

Origin: from rough feeling in the anteromedial angle of the floor of orbit, lateral to the lacrimal groove.

Insertion: into sclera supporting the equator in the posterosuperior quadrant of the eyeball a little below and posterior to the insertion of superior oblique.

Nerve Supply: all the extraocular muscles that move the eyeball are supplied by the oculomotor nerve (CN3) with the exception of lateral rectus and superior oblique that are supplied by the abducent nerve (CN6) and trochlear nerve, respectively [mnemonic: LR6, S04, i.e ” LR (lateral rectus) by 6 CN and SO (superior oblique) by 4 CN]

Activities of Muscles on the Eyeball

Extraocular Muscles: Muscle Activity

Both eyes face forwards and their long axes (visual optic axes) is located in sagittal plane, parallel with every other and with medial walls of the orbits. The lateral walls of orbits slope backwards and medially making a right (90°) angle with every other. The ocular muscles and optic nerve come from the apex of the orbit near the rear of the medial wall and pass forwards and laterally to be connected to the eyeball. The activities of superior and inferior recti are, consequently, not straight, despite their name. The superior and inferior oblique muscles, consequently, have to act in concert with 2 recti to be able to generate direct upward and downward movements of the eyeball.

Axis of Movements of the Eyeball

Elevation and depression: around the transverse axis going through the equator.

Adduction and abduction: around the vertical axis going through the equator.

Rotation (torsion): around the anteroposterior axis stretching from anterior post to posterior pole of the eyeball.

When 12 o’clock position of the cornea rotates medially, it is named intorsion and when it rotates laterally, it termed extorsion.

Activities of Individual Muscles

The activities of individual muscles are easily deduced from Starling’s diagram.

Extraocular Muscles: Activities of Muscles

They’re as follows:

Superior rectus (SR): elevation, adduction and intorsion.
Inferior rectus (IR): depression, adduction and extorsion.
Medial rectus (MR): adduction.
Lateral rectus (LR): abduction.
Superior oblique (SO): depression, abduction and intorsion.
Inferior oblique (IO): elevation, abduction and extorsion.

Related Movements of the Eyeball

Conjugate movements: when both the eyes move in exactly the same way with visual axes being parallel.

Disconjugate movements: when the axes of both eyes converge or diverge.

Clinical Significance

Strabismus/squint: Unilateral paralysis of an individual muscle as a result of engagement of the nerves creates strabismus or squint (deviation of eye to the opposite side) and may lead to diplopia (double vision). In diplopia, the light from an object isn’t focused on the indistinguishable regions of both retinae. The actual image falls on the macula of the unaffected eye and fictitious image falls on the peripheral part of retina of the paralyzed eye. The examples are as under:

Muscle paralyzed Nerve included Effects.
Lateral rectus Abducent Medial squint.
Medial rectus Oculomotor Lateral squint.

LevatorpalpebraeSuperioris (Lps) Muscle

Origin

From undersurface of the lesser wing of sphenoid in the apex of the orbit, above the common tendinous ring by a narrow tendon.

Insertion

The muscle expands as it enters forwards from its origin and splits into 3 lamellae:

Upper lamella being composed of skeletal muscle enters the orbital septum goes through the fibres of orbicularis oculi to be added into the skin of upper eyelid.
Intermediate lamella being composed of smooth muscle (superior tarsal muscle) is added on to the upper border of the superior tarsal plate.
Lower lamella being composed of connective tissue is added on to the superior fornix of the conjunctiva.

Nerve Supply

Striped (skeletal muscle) part is supplied by the upper section of oculomotor nerve.

Unstriped (smooth muscle) part is supplied by the post-

Medial Rectus And Inferior Oblique Dmg