EOMs Flashcards
What are intrinsic muscles?
This mean involuntary movement
- ciliary muscles, iris sphincter, iris dilator
- movement of internal ocular structures
What are extrinsic muscles?
Voluntary eye movement
- EOMs
- Movement of the globe
What is a striated muscle?
Specialised for forceful contractions of short duration
surrounded by CT sheath: epimysium
What is a sarcolemma?
This invaginates to form transverse or T tubules, which allow rapid spread of ions in response to action potentials
What is a Sarcoplasm?
equivalent to cell cytoplasm. Contains normal cell structure (e.g. mitochondria) and also myofibrils
What is a thick myofibril?
Formed of subunits called myosin.
Long and slender; the backbone of the myofibril
What is a thin myofibril?
Formed of protein ‘actin’, double helical arrangement
What is Fick’s Axes?
It is helpful to define movements relative to a point
it is divided into quadrants, intersecting at notional centre of rotation, 13.5mm behind the cornea
What is the medial rectus muscle?
Originates from upper and lower parts of common tendinous ring and from sheath of optic nerve
Largest of the oculomotor muscles
What is the lateral rectus muscle?
Originates on both parts of annulus of Zinn and spina recti lateralis
What is the superior rectus muscle?
Originates superior part annulus of Zinn and sheath of optic nerve
What is the inferior rectus muscle?
This originates on the lower portion of Annulus of Zinn
What is the superior oblique muscle?
This originates on the lesser wing of the sphenoid bone
It is the longest and thinnest EOM and crosses medially to laterally
It passes through the trochlea and runs posteriorly
What is the inferior oblique muscle?
It originates on the maxillary bone
It inserts posteriorly on the globe and runs the opposite direction to the SO
How are the fibres arranged in the global layer?
- Adjacent to the globe
- Fibres of various diameters
- Runs along muscle
- Attached at origin and insertion
- Inserts into sclera allowing/ causing movement
