Extraocular muscles Flashcards
How many oculomotor muscle do we have?
- six
What are these muscles?
- 4 recti muscles: medial, lateral, superior, and inferior
- 2 Oblique muscles: superior and and inferior
What are the nerves involved?
oculomotor, trochlear, abducens
What is the origin of all the four recti muscles?
The ZINN ring- annular tendon
where is the annulus of ZINN?
attached to the edge of the optic canal on the sub-optic tubercle and the medial part of the superior orbital fissure
divisions of ZINN tendon?
Superomedial
Superolateral
inferomedial
Inferolateral
how the recti muscles oriiginate from the ZINN
will gather 2 by 2 to form the origin of each muscle
What is the spiral of Tillaux?
line connecting the insertion points of the four rectus muscles on the sclera
Cite the muscle order in the spiral of Tillaux?
- Medial Rectus: Inserts closest to the limbus (5.5 mm).
- Inferior Rectus: Next (6.5 mm).
- Lateral Rectus: Further out (6.9 mm).
- Superior Rectus: Inserts farthest (7.7 mm).
The origin of the superior oblique muscle?
- at the level of the Zinn tendon
- little above and inside the optical hole
- inside the insertion of the levator palpebrae superioris.
- lies between the origins of superior and inferior recti
What are the two parts of the superior oblique muscle?
- Direct part : From its origin to the trochlea.
- Reflective part : Tendinous, from trochlea to eyeball.
The course of superior oblique muscle?
- first part: muscular body( 30 mm), between the medial rectus and the superior rectus
- second part: tendon part( 20 mm), under the superior rectus
What is the origin of the inferior oblique muscle?
the floor of the orbit
outside the orifice of the nasolacrimal duct.
The course of the inferior oblique muscle?
passes under the inferior rectus
where the inferior oblique muscle terminate?
- the inferior and lateral quadrant of the posterior hemisphere
- ends fibrous expansions to the lower edge of the lateral rectus.
What is a MUSCLE SHEATHS?
surround each oculomotor muscle
intermuscular membrane or septa?
connect the The sheaths of the ocular muscles are connected to each other
- in the anterior portion of the orbit
the intermuscular membrane divides the orbital fat into in the coronal plane viewed as a ring?
- The intraconal portion
- The extraconal portion
Action of Medial rectus?
- Adduction
Action of lateral rectus?
Abduction
Action of the Inferior rectus?
- Depression
- Extorsion
- Adduction
Action of the superior rectus?
- Elevation
- Intorsion
- Adduction
Action of the inferior oblique?
- Extorsion
- Elevation
- Abduction
Action of the inferior oblique?
- Intorsion
- Elavation
- Abduction
Muscle arteries branch of?
ophthalmic arteries
what is the constant muscular artery?
Lower muscular arteries
What are the muscles supplied by the lower muscular arteries?
- Medial, lateral, and inferior recti
- inferior oblique muscle
What are less constant arteries?
- Lateral, medial, superior muscular arteries?
Venous vascularization?
- episcleric veins < superior ophthalmic vein < the cavernous sinus
Lymphatics?
we don’t know
Innervation?
- LR: 6
- SO: 4
- rest: 3
paralysis of the muscle?
- paralytic strabismus, diplopia
