EXTRAOCULAR MUSCLES

Explanation:

Suspensory ligament of the eye ball [Ref. Gray’s Anatomy 40/e p658; Last’s anatomy: regional and applied By Chummy S. Sinnatamby, Raymond Jack Last 11/e p417; Clinical anatomy of the eye By Richard S. Snell, Michael A. Lemp p133]

• The suspensory ligament (of Lockwood) is a part of fascial sheath encasing the eye ball. It forms a hammock stretching below the eyeball between the medial and lateral check ligaments and enclosing the inferior rectus and inferior oblique muscles of the eye.
• The ligament supports the eye, and prevents downward displacement of it.
• Gray’s 40/e p658 writes- “A continuous fascial band, the suspensory ligament of the eye, is slung like a hammock below the eye, providing sufficient support such that, even when the maxilla (forming the floor of the orbit) is removed, the eye will retain its position.”

Explanation:

Superior oblique

Explanation: All the extra ocular muscles except inferior oblique arise from the apex of orbit. Inferior oblique arises from lower and inner orbital walls near the lacrimal fossa and inserts in the sclera below and lateral to the posterior pole of the globe.

Ref: Parsons’ 21st / Pg. 393.

Explanation: Superior oblique is the longest and thinnest of the ocular muscles. It originates above and medial to the optic foramen and partially overlaps the origin of the levator palpebrae superioris muscle. It has a thin, fusiform belly and passes anteriorly in the form of a tendon to its trochlea. It is then reflected backwards and downwards as a further length of tendon to attach in a fan shape to the sclera beneath the superior rectus.

Superior oblique is innervated by trochlear nerve. Inferior oblique, medial rectus, superior rectus, inferior rectus are innervated by occulomotor nerve. Lateral rectus is innervated by abducens nerve.

Ref: Riordan-Eva P. (2011). Chapter 1. Anatomy & Embryology of the Eye. In P. Riordan-Eva, E.T. Cunningham, Jr. (Eds), Vaughan & Asbury’s General Ophthalmology, 18e.

Explanation:

Ref: Textbook of Ophthalmology edited by Sunita Agarwal, page 404.

Explanation:

A. i.e. Superior division of 3^rd nerve

Superior rectus & LPS are supplied by superior division of occulomotor nerveQ.

Explanation:

–  All extraocular muscles (all recti, superior oblique & levator palpebrae superioris) except inferior oblique arise from apex of orbit.

The inferior rectus muscle originates from the inferior edge of the common tendinous ring (annulus of Zinn).

It courses anteriorly, laterally and downwards along the orbital floor to insert on sclera anteriorly about 6.5 cm behind the limbus. Inferior rectus muscle courses between the eyeball and inferior oblique muscle (which passes beneath i. e. inferior to inferior rectus) before its insertion.

Failure to dissect fascial attachments b/w inferior rectus, the inferior oblique, and lower lid retractors during IR recession or resection may cause eyelid fissure widening or narrowing, respectively.

Explanation:

C i.e., Extorsion

Explanation:

B i.e., Inferior rectus

Explanation:

A i.e., 3^rd

Explanation:

A i.e., Lateral rectus B i.e., Superior oblique

Explanation:

C i.e. Superior oblique

Explanation:

C i.e. Depression with internal rotation

Explanation:

A i.e. Intortion

Explanation:

A i.e. Extortion

Superior oblique – intort, depress & abduct Q the eye in primary position; whereas inferior oblique-extort, elevate & abduct Q the eye in primary position.

Muscle	Action
Superior oblique & Superior rectus	IntortorsQ
Inferior oblique & Inferior rectus	ExtortorsQ
Mnemonic – ‘!Superiors = Intortors & Inferiors= Extortors”

 

Medial rectus + Superior & Inferior rectus	AdductorsQ;
Lateral rectus + Superior &	AbductorsQ
Inferior oblique
Mnemonic – “BOLR” i.e. aBductor = Oblique (sup. &
inf.), + Lateral Rectus
Mnemonic – “MIS RED” i.e. Medial/Inferior/ Superior
REctus are aDDuctors

 

Superior rectus & Inferior oblique	Elevators
Inferior rectus & Superior oblique	Depressor

 

In aBducted eye ObliquesQ are chief tortors
	Mnemonic= “BORD”
In aDDucted eye RectiQ are chief tortors

 

Action of individual muscles
Muscle	In primary	Abducted	Adducted
	position	eye	eye
1. Superior	DepressionQ	Only	Only
oblique	A bductionQ	intortion	depression
	IntortionQ
2. Inferior	Elevation	Only	Only
oblique	Abduction	extortion	elevation
	Extortion
3. Inferior	Depression	Only	Only
rectus	Adduction	depression	extortion
	Extortion
4. Superior	Elevation	Only	Only
rectus	Adduction	elevation	intortion
	Intortion
5. Medial rectus	Only adduction		‑
6. Lateral rectus	Only abduction	–	‑

Mn =”SO BID BEXT IFO=So BID BEST IPO” = Superior Oblique = aBduction, Intorsion, Depression; Inferior Oblique = aBduction, Elevation, Extorsion

Explanation:

A i.e. Polymyositis

Ocular muscles are spared even in advanced, untreated cases of inflammatory myopathies (polymyositis, dermatomyositis & inclusion body myositis) Q. If these muscles are affected, the diagnosis of inflammatory myopathy should be questioned. (H-2540)

Inflammatory Myopathies

Characteristic	Dermatomyositis	Polymyositis	Inclusion body myositis
Age	Adulthood and childhood	> 18 years	> 50 years Male: Female = 3:1
Sex	Female > Male
Familial association	Absent	Absent	Present in some cases

Associated conditions

Explanation:

Ans. Superior oblique

Explanation:

Ans. Inferior oblique

Explanation:

Ans. Inferior oblique

Explanation:

Ans. Left inferior oblique

Explanation:

Ans. Muller’s muscle

Explanation:

Ans. Superior oblique

Explanation:

Ans. Superior rectus

Explanation:

Ans. Dextrodepression

Explanation:

Ans. Superior oblique

Explanation:

Superior rectus muscle

It is innervated by the superior division of the oculomotor nerve (Cranial Nerve III).

In the primary position (looking straight ahead), the superior rectus muscle’s primary function is elevation, although it also contributes to intorsion and adduction.

Explanation:

Lateral rectus

It control abduction 

It is the only muscle innervated by the abducens nerve i.e., cranial nerve VI.

Superior oblique muscle is supplied by the Trochlear nerve and the rest of the extraocular muscles are supplied by the oculomotor nerve.

Explanation:

Superior oblique

The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit.

It can be used to divide the regions of the superior orbital fissure.

The arteries surrounding the optic nerve are sometimes called the “circle of Zinn-Haller” (CZH).

Some sources distinguish between these terms more precisely, with the anulus tendineus communis being the parent structure, divided into two parts:

• A lower, the ligament or tendon of Zinn, which gives origin to the Rectus inferior, part of the Rectus internus, and the lower head of origin of the Rectus lateralis.
• An upper, which gives origin to the Rectus superior, the rest of the Rectus medialis, and the upper head of the Rectus lateralis. This upper band is sometimes termed the superior tendon of Lockwood.

The site of origin of the superior oblique muscle is from the lesser wing of the sphenoid above the optic canal.

Explanation:

Single/pure movements-produced as a result of combined actions of muscles.

• Upward rotation/elevation-superior rectus and inferior oblique
• Downward rotation/depression-inferior rectus and superior oblique
• Medial rotation/adduction-superior rectus, medial rectus and inferior rectus
• Lateral rotation/abduction-superior rectus, lateral rectus and inferior rectus
• Intortion-superior oblique and superior rectus
• Extortion-inferior oblique and inferior rectus

Explanation:

The primary action of the superior oblique muscle is intorsion (internal rotation), the secondary action is depression (primarily in the adducted position) and the tertiary action is abduction.

Explanation:

Trochlear nerve ends by supplying the superior oblique muscle on its orbital surface Remember

• SO-4, LR-6, Rest by 3
• Superior oblique by 4^th cranial nerve
• Lateral rectus by 6^th cranial nerve
• Rest of the muscles by 3^rd cranial nerve

Explanation:

Ans. B: Fourth cranial nerve

Each extraocular muscle is innervated by a specific cranial nerve:

1. Medial rectus (MR) — cranial nerve III (Oculomotor)
2. Lateral rectus (LR) — cranial nerve VI (Abducens)
3. Superior rectus (SR) — cranial nerve III (Oculomotor)
4. Inferior rectus (IR) — cranial nerve III (Oculomotor)
5. Superior oblique (SO)—cranial nerve IV (Trochlear)
6. Inferior oblique (I0) —cranial nerve III (Oculomotor)

 The following can be used to remember the cranial nerve innervations of the six extraocular muscles:

LR6 (SO4)3.

That is, the lateral rectus (LR) is innervated by C.N. 6, the superior oblique (SO) is innervated by C.N. 4, and the four remaining muscles (MR, SR, IR, and RD) are innervated by C.N. 3.

Explanation:

Ans. is ‘c’ i.e., Extorsion

Explanation:

Ans. is ‘b’ i.e., Elevation

Explanation:

Ans. is ‘c’ i.e., Lateral rectus

Lateral rectus is supplied of by sixth nerve (abducent) nerve and superior oblique is supplied by fourth (trochlear) nerve. All other extraocular muscles are supplied by occulmotor nerve.

Explanation:

Ans. is ‘c’ i.e., Right superior rectus

To know this question one should know the difference between synergistic muscles and yoke muscles.

Synergists. It refers to the muscles having the same primary action in the same eye e.g.,superior rectus and inferior oblique of the same eye act as synergistic elevators.

Explanation:

Ans. is ‘b’ i.e., Right superior rectus and left inferior oblique

(Dextroelevation) 
Right superior rectus 
Left inferior oblique

Explanation:

Ans. is ‘c’ i.e., Lateral rectus