What is the extraocular muscle that does not originate at the annulus of Zinn

The inferior oblique (IO) muscle is the only EOM that does not arise from the orbital apex, but rather originates from the lateral border of the lacrimal fossa, which is anterior and nasal within the orbit.

What muscles originate from the annulus of Zinn?

The annulus of Zinn is a dense, fibrous ring of connective tissue located at the apex of the orbit that is the origin of four of the six extraocular muscles – the superior rectus, inferior rectus, lateral rectus, and medial rectus.

Which structure does not pass through the annulus of Zinn?

The lacrimal, frontal and trochlear nerves, as well as the ophthalmic vein, pass through the superior orbital fissure outside of the annulus of Zinn. The superior and inferior divisions of cranial nerve III, cranial nerve VI, and the nasociliary nerve pass through the fissure within the Annulus of Zinn.

Which extraocular eye muscle does not originate at the common tendinous ring?

The superior oblique is one of the two noteworthy oblique extraocular muscles. These muscles are unique in that they do not originate from the common tendinous ring, have an angular attachment to the eyeball, and they attach to the posterior aspect of the eyeball.

What is in the annulus of Zinn?

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 is the common origin of the four rectus muscles of the group of extraocular muscles. … Optic nerve. Annular muscles are found near pharynx.

Is the levator Palpebrae Superioris in extraocular muscle?

MuscleLevator palpebrae superiorisInnervationOculomotor nerveOriginSphenoid boneInsertionTarsal plate of upper eyelidPrimary actionElevation/retraction of the upper eyelid

Where are the extraocular muscles located?

These muscles originate in the eye socket (orbit) and work to move the eye up, down, side to side, and rotate the eye. The superior rectus is an extraocular muscle that attaches to the top of the eye. It moves the eye upward. The inferior rectus is an extraocular muscle that attaches to the bottom of the eye.

What is common tendinous ring?

The tendinous ring, also known as the annulus of Zinn, is the common origin of the four rectus muscles (extraocular muscles). The tendinous ring straddles the lower, medial part of the superior orbital fissure.

Which of the extraocular muscle does not originate from the orbital apex?

The inferior oblique (IO) muscle is the only EOM that does not arise from the orbital apex, but rather originates from the lateral border of the lacrimal fossa, which is anterior and nasal within the orbit.

Which cranial nerves innervate the extraocular muscles?

The extraocular muscles are innervated by lower motor neurons that form three cranial nerves: the abducens, the trochlear, and the oculomotor (Figure 20.3). The abducens nerve (cranial nerve VI) exits the brainstem from the pons-medullary junction and innervates the lateral rectus muscle.

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Where does the superior oblique originate?

The superior oblique muscle has its origin on the lesser wing of the sphenoid bone, medial to the optic canal near the frontoethmoid suture. The muscle courses forward and passes through the trochlea, a U-shaped piece of cartilage attached to the orbital plate of the frontal bone (see Figure 10-7).

Where does the inferior oblique muscle originate?

The inferior oblique muscle has its origin on the maxillary bone just posterior to the inferior medial orbital rim and lateral to the nasolacrimal canal. The inferior oblique is the only extraocular muscle to have its anatomic origin in the anterior orbit.

What structures pass through inferior fissures?

Infraorbital nerve.
Zygomatic nerve.
Parasympathetics to lacrimal gland.
Infraorbital artery.
Infraorbital vein.
Inferior ophthalmic vein branch to pterygoid plexus.

What is the superior oblique muscle?

The superior oblique is a fusiform (spindle-shaped) muscle belonging to the extraocular group of muscles. It originates near the nose. … The fourth cranial (trochlear) nerve supplies only this muscle and it supports the eye’s ability to depress downward.

Which nerve does not transverse the middle part of superior orbital fissure?

Middle part transmits: Superior and inferior divisions of the oculomotor nerve (CN III), nasociliary nerve (lies between the two divisions of oculomotor nerve) and abducent nerve. Medial part transmits: Inferior ophthalmic veins and sympathetic nerves arising from the plexus that accompanies the internal carotid artery.

What are extraocular muscles?

Six muscles outside the eye govern its movements. These muscles are the four rectus muscles—the inferior, medial, lateral, and superior recti—and the superior and inferior oblique muscles. The tendon is attached to the sclera back of the equator of the eye. …

Are extraocular muscles skeletal?

Extraocular muscles are among the fastest and most fatigue-resistant skeletal muscles. Their highly specialized function, to move a sensory organ, the eyeball, is reflected in their specific MHC content and the multiplicity of fiber types.

What is the acronym for extraocular muscles?

Medical Definition of extraocular muscle : any of six small voluntary muscles that pass between the eyeball and the orbit and control the movement and stabilization of the eyeball in relation to the orbit —abbreviation EOM — see oblique sense b, rectus sense 2. More from Merriam-Webster on extraocular muscle.

What is the origin of the levator Palpebrae Superioris?

Structure and Function The levator palpebrae superioris muscle origin is the periosteum of the lesser wing of the sphenoid bone, superior to the optic foramen. The muscle travels anteriorly along the superior aspect of the orbit superior to the superior rectus muscle.

What Innervates the levator Palpebrae Superioris muscle?

Background: The levator palpebrae superioris muscle (LPS) acts as the upper eyelid’s major elevator and retractor and is innervated by the oculomotor nerve. The muscle’s paralysis is manifested by ptosis.

What are the extraocular muscles of the orbit?

Attachments: Originates from the body of the sphenoid bone. …
Actions: Depresses, abducts and medially rotates the eyeball.

Which of the following is not an eye muscle?

The inferior oblique muscle (b) is not an intrinsic eye muscle.

How many nerves innervate the six extraocular muscles?

The extraocular muscles execute eye movements and are innervated by three cranial nerves.

What is Nasociliary nerve?

The nasociliary nerve is the sensory nerve to the eye. It enters the orbit through the superior orbital fissure, inside the cone formed by the muscles of the globe. It is on a lower plane, therefore, than the lacrimal and frontal nerves. … This communicating branch passes to the ciliary ganglion (see Abducens Nerve).

Which of the following cranial nerves does not innervate extrinsic muscles?

Question: Which of the following cranial nerves does not innervate extrinsic eye muscles? (e) Trigeminal.

What is primary secondary and tertiary actions of extraocular muscles?

The primary actions of the inferior and superior obliques are excyclo and incyclotorsion, their secondary actions are elevation and depression and their tertiary action is abduction.

What Innervates the superior rectus muscle?

The superior rectus is innervated by the superior division of the oculomotor nerve, which enters the muscle on its inferior face. Branches pass either through the muscle or around it to innervate the levator.

Where is superior oblique located?

The superior oblique muscle is situated in the upper medial portion of the orbit, adjacent to its medial wall. The muscle is located superior to medial rectus and medial to both the superior rectus and levator palpebrae superioris muscles.

Which muscles are obliques?

Oblique muscle refers to two abdominal muscles – the external and internal obliques. These provide trunk flexion and rotation. The external oblique is the thickest and runs from the lower ribs to the iliac crest.

What is the origin of the obliquus capitis inferior?

The obliquus capitis inferior muscle is the larger of the two obliquus muscles. It originates on the spinous process of C2, passes laterally and lightly superiorly to insert onto the transverse process of C1.