extraocular muscles Flashcards
where are the extraocular muscles located?
within the orbit, but are extrinsic and separate from the eyeball itself
relationship between eyeball and extraocular muscles?
E. muscles are extrinsic and separate from the eyeball itself
what do the extraocular muscles function to do?
They act to control the movements of the eyeball and the superior eyelid
how many extraocular muscles are there?
seven extraocular muscles
what are the 7 extraocular muscles?
the levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique and superior oblique
functionally, how can the 7 extraocular muscles be divided?
Responsible for eye movement
Responsible for superior eyelid movement
what are the muscles responsible for eye movement?
Recti and oblique muscles
what are the muscles responsible for superior eyelid movement?
Levator palpebrae superioris
what is the levator palpebrae superioris (LPS) muscle involed in?
the only muscle involved in raising the superior eyelid
what does a small portion of the LPS muscle contain?
a collection of smooth muscle fibres – known as the superior tarsal muscle
in contrast to the LPS, what is the superior tarsal muscle innervated by?
the sympathetic nervous system
origin of of LPS?
Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen
attachment of LPS?
superior tarsal plate of the upper eyelid (a thick plate of connective tissue)
action of LPS?
Elevates the upper eyelid
innervation of LPS?
by the oculomotor nerve (CN III)
where is the superior tarsal muscle located?
within the LPS
what is the superior tarsal muscle innervated by?
the sympathetic nervous system
what is Horner’s syndrome?
a triad of symptoms produced by damage to the sympathetic trunk in the neck
what is the triad of symptoms within Horner’s syndrome?
partial ptosis
miosis
anhydrosis
what is partial ptosis?
dropping of eyelid
why does partial ptosis occur?
due to denervation of superior tarsal muscle (within LPS)
what is miosis?
pupillary constriction
why does miosis occur?
due to denervation of dilator pupillae muscle
what is anhydrosis?
absence of sweating
where does anhydrosis occur within Horner’s syndrome?
on the ipsilateral side of the face
why does anhydrosis occur?
denervation of sweat glands
what can Horner’s syndrome represent?
serious pathology:
tumour of apex of lung (Pancoast tumour)
aortic aneurysm
thyroid carcinoma
