The extraocular muscles are situated within the orbit, but are extrinsic and separate from the eyeball itself. They plot to regulate the motions of the eyeball and also the superior eyelid.
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There are seven extraocular muscles – the levator palpebrae superioris, exceptional rectus, worse rectus, medial rectus, lateral rectus, worse oblique and also superior oblique. Functionally, they can be divided into two groups:Responsible because that eye movement – Recti and also oblique muscles.Responsible for remarkable eyelid movement – Levator palpebrae superioris.
In this article, we shall look in ~ the anatomy the the extraocular muscle – your attachments, innervation and also actions.
Levator Palpebrae Superioris
The levator palpebrae superioris (LPS) is the just muscle associated in increasing the exceptional eyelid. A small portion of this muscle contains a collection of smooth muscle fibres – known as the remarkable tarsal muscle. In comparison to the LPS, the superior tarsal muscle is innervated by the sympathetic concerned system.Actions: Elevates the top eyelid.
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Fig 1 – attachments of the levator palpebrae superiors to the premium tarsal plate.
Muscles of Eye Movement
There are 6 muscles connected in the regulate of the eyeball itself. They can be separated into two groups; the 4 recti muscles, and the 2 oblique muscles.
There are 4 recti muscles; remarkable rectus, worse rectus, medial rectus and also lateral rectus.
These muscles characteristically originate from the common tendinous ring. This is a ring that fibrous tissue, which surrounding the optic canal at the earlier of the orbit. From their origin, the muscles pass anteriorly to attach to the sclera that the eyeball.
The surname recti is obtained from the latin because that ‘straight’ – this to represent the reality that the recti muscles have actually a direct path from beginning to attachment. This is in contrast with the tilt eye muscles, which have an angular approach to the eyeball.
Superior RectusAttachments: Originates indigenous the superior component of the common tendinous ring, and attaches come the superior and anterior element of the sclera.Actions: key movement is elevation. Also contributes come adduction and also medial rotation of the eyeball.
Inferior RectusAttachments: Originates native the inferior part of the usual tendinous ring, and also attaches to the inferior and anterior element of the sclera.Actions: Main movement is depression. Also contributes to adduction and also lateral rotation the the eyeball.
Medial RectusAttachments: Originates from the medial part of the common tendinous ring, and also attaches to the anteromedial facet of the sclera.Actions: Adducts the eyeball.
Lateral RectusAttachments: Originates native the lateral component of the typical tendinous ring, and attaches to the anterolateral aspect of the sclera.Actions: Abducts the eyeball.
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Fig 2 – Lateral see of the extraocular muscles.
There room two oblique muscles – the superior and inferior obliques. Uneven the recti group of muscles, they carry out not originate indigenous the usual tendinous ring.
From your origin, the oblique muscles take an angular approach to the eyeball (in comparison to the straight method of the recti muscles). They affix to the posterior surface ar of the sclera.
Superior ObliqueActions: Depresses, abducts and also medially rotates the eyeball.
Inferior ObliqueAttachments: Originates native the anterior element of the orbital floor. Attaches to the sclera the the eye, posterior to the lateral rectusActions: Elevates, abducts and also laterally rotates the eyeball.
Clinical Relevance: Cranial Nerve Palsies
The extraocular muscles room innervated by 3 cranial nerves. Damages to among the cranial nerves will reason paralysis that its corresponding muscles. This will alter the relaxing gaze that the impacted eye. Thus, a lesion of every cranial nerve has its very own characteristic appearance:
(A great tool to remember the innervation that the extraocular muscles is LR6 – SO4 – R3)
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Fig 3 – appropriate oculomotor nerve palsy, qualified by the ‘down and out’ dilated pupil with ipsilateral ptosis
Clinical Relevance: Horner’s Syndrome
Fig 4 – Left face Horner’s syndrome. Keep in mind the partial ptosis.
Horner’s syndrome refers to a triad of symptoms produced by damages to the sympathetic trunk in the neck:Partial ptosis (drooping the the top eyelid) – as result of denervation of the superior tarsal muscle.Miosis (pupillary constriction) – due to denervation of the dilator pupillae muscle.Anhidrosis (absence of sweating) ~ above the ipsilateral next of the face – because of denervation of the sweat glands.
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Horner’s syndrome deserve to represent serious pathology, such together a tumour the the apex of the lung (Pancoast tumour), aortic aneurysm or thryoid carcinoma.