Extraocular Muscles, Innervation, and Eye Movements

Flashcards covering the extraocular muscles, their innervations (cranial nerves III, IV, VI), axes of eye movement, anatomical actions, and clinical testing patterns.

What are the two movements that occur along the horizontal axis of the eyeball?

Abduction and Adduction

What are the two movements that occur along the vertical axis of the eyeball?

Elevation and Depression

What are the two movements that describe pivotal movement of the eyeball?

Intorsion and Extorsion

Which cranial nerve innervates the lateral rectus muscle (LR)?

$\text{CN VI}$ (Cranial Nerve $6$)

Which cranial nerve innervates the superior oblique muscle (SO)?

$\text{CN IV}$ (Cranial Nerve $4$)

Which cranial nerve innervates the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles?

$\text{CN III}$ (Cranial Nerve $3$)

What does the clinical rule or mnemonic "LR SO R 6 4 3" signify regarding the extraocular muscles?

Lateral Rectus is innervated by CN $6$, Superior Oblique is innervated by CN $4$, and the Rest of the muscles are innervated by CN $3$.

In this superior view of the right orbit, which muscle passes anteriorly and loops through the trochlea before inserting on the eyeball?

Superior oblique muscle (SO)

What is the primary anatomical action of the lateral rectus muscle?

Abducts eye

What is the primary anatomical action of the medial rectus muscle?

Adducts eye

Which extra-ocular muscle is responsible for the anatomical action of directing the right eye "Up and In"?

SR (Superior rectus muscle)

Which extra-ocular muscle produces the anatomical movement directing the right eye "Up and Out"?

Inferior oblique muscle (IO)

Which extra-ocular muscle produces the anatomical movement directing the right eye "Down and out"?

Superior oblique muscle (SO)

Which extra-ocular muscle produces the anatomical movement directing the right eye "Down and in"?

Inferior rectus muscle (IR)

According to the clinical testing diagram for the right eye, which muscle is isolated and tested when the patient gazes down and inward (adduction and depression)?

Superior oblique muscle (SO)

In clinical testing of the eye muscles, which direction of gaze isolates and tests the inferior oblique muscle (IO)?

Up and in (elevation in adduction)

In clinical testing of the eye muscles, which direction of gaze isolates and tests the superior rectus muscle (SR)?

Up and out (elevation in abduction)

In clinical testing of the eye muscles, which direction of gaze isolates and tests the inferior rectus muscle (IR)?

Down and out (depression in abduction)

What vertical movement of the eyeball is demonstrated in this image?

Elevation

What vertical movement of the eyeball is demonstrated in this image?

Depression