The tendinous ring, also known as the annulus of Zinn, is the common origin of the four rectus muscles (extraocular muscles
What makes up the common tendinous ring?
a fibrous ring that surrounds the optic canal and the medial part of the superior orbital fissure; it gives origin to the four rectus muscles of the eye and is partially fused with the sheath of the optic nerve. Synonym: annulus tendineus communis, Zinn’s ligament, Zinn’s ring, Zinn’s tendon.
What nerves go through common tendinous ring?
- superior division of the oculomotor nerve (CN III)
- nasociliary nerve (a branch of the ophthalmic nerve)
- inferior division of the oculomotor nerve (CN III)
- abducens nerve (CN VI)
What is Tendinous ring of Zinn?
Anatomical terminology 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.Does optic nerve pass through common tendinous ring?
The optic, oculomotor, and abducens nerves all pass through the annulus of Zinn, while the trochlear nerve travels just medial to the annulus of Zinn. The nasociliary nerve is the sole portion of the ophthalmic division of cranial nerve V which passes through the annulus of Zinn.
Where is the levator Palpebrae Superioris?
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 passes through Tendinous ring of orbit?
The tendinous ring straddles the lower, medial part of the superior orbital fissure. It attaches to a tubercle on the greater wing of the sphenoid bone (at the margin of the superior orbital fissure). Through it (from superior to inferior) pass: superior division of the oculomotor nerve (CN III)
Which extraocular muscle does not arise from the tendinous ring of the orbit?
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.Which of the following muscles does not take its origin from the common tendinous ring?
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. Figure 2. Bony orbit with the tendinous annulus indicated in the orbital apex by the black oval.
Which of the following origins of the extraocular muscle does not form the common tendinous ring of the orbit?Along the floor of the orbit is the origin of the inferior oblique muscle. This is the only extraocular muscle that does not originate at the apex of the orbit. The lateral orbital wall is formed by two bones: the zygomatic bone and the greater wing of the sphenoid.
Article first time published onWhat muscle elevates the eyeball?
The first of these muscles, the superior rectus muscle, elevates the eye, allowing the eye to look up. The antagonist of the superior rectus muscle is the inferior rectus muscle, which depresses the eye, allowing the eye to look down.
What is the apex of the orbit?
Background. The orbital apex is the most posterior portion of the pyramidal-shaped orbit, positioned at the craniofacial junction. The anatomy of the orbital apex is significant for the complex association between bony, neural, and vascular elements.
What does lacrimal nerve do?
Function. The lacrimal nerve provides sensory innervation to the lacrimal gland, conjunctiva of the lateral upper eyelid and superior fornix, the skin of the lateral forehead, scalp and lateral upper eyelid.
What is 6th cranial nerve?
Cranial nerve six (CN VI), also known as the abducens nerve, is one of the nerves responsible for the extraocular motor functions of the eye, along with the oculomotor nerve (CN III) and the trochlear nerve (CN IV).
What is ophthalmic nerve?
The ophthalmic nerve is the first branch of the trigeminal nerve, which is also known as the fifth cranial nerve. The ophthalmic nerve supplies sensory innervation to the structures of the eye, including the cornea, ciliary body, lacrimal gland, and conjunctiva.
Which is the shortest EOM?
The inferior oblique muscle has the shortest tendon of all the extraocular muscles (0-1 mm).
What artery passes through optic canal?
The optic canal is a very important structure due to the structures that pass through this canal, mainly the optic nerve and the ophthalmic artery.
What travels through superior orbital fissure?
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.
Is the levator Palpebrae Superioris in extraocular muscle?
MuscleLevator palpebrae superiorisInnervationOculomotor nerveOriginSphenoid boneInsertionTarsal plate of upper eyelidPrimary actionElevation/retraction of the upper eyelid
What is the Palpebrae?
1. palpebra – either of two folds of skin that can be moved to cover or open the eye; “his lids would stay open no longer” eyelid, lid. eye, oculus, optic – the organ of sight. protective fold – a flap of tissue that protects what it covers.
What Innervates the levator Palpebrae?
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 nerve controls the levator Palpebrae Superioris?
The striated levator palpebrae superioris (LPS) muscle is innervated by the oculomotor nerve, and has a common origin with the superior rectus muscle. Anteriorly, it becomes the levator aponeurosis as it passes anterior to Whitnall ligament, and inserts into the anterior tarsal surface.
What is the eye muscle called?
The human eye has six eye muscles. They are split into two primary groups: the recti muscles and the oblique muscles. The four recti muscles are the lateral rectus, the medial rectus, the inferior rectus, and the superior rectus while the two oblique muscles are the inferior oblique and the superior oblique.
What are extraocular eye movements?
The extraocular muscles execute eye movements and are innervated by three cranial nerves. … Contraction of the medial rectus pulls the eye towards the nose (adduction or medial movement). Contraction of the lateral rectus pulls the eye away from the nose (abduction or lateral movement).
What are the six muscles of the eye and their definitions functions?
- Medial Rectus. The medial rectus is the largest extraocular movement muscle. …
- Superior Rectus. This muscle controls the eye’s upward movement. …
- Inferior Rectus. Opposite to the superior rectus, this muscle moves the eyeball downward. …
- Superior Oblique. …
- Inferior Oblique.
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.
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.
What extraocular muscle does not originate at the annulus of Zinn?
[2] Unlike all other extraocular muscles, the inferior oblique does not originate from the annulus of Zinn or common tendinous ring. Instead, the inferior oblique originates from the orbital floor just lateral to the nasolacrimal groove.
What is extraocular muscle?
The extraocular muscles are the six muscles that control the movements of the eyes. For reasons we don’t fully understand, these muscles can be particularly affected by myasthenia.
What is the common purpose of the oculomotor Trochlear and Abducens cranial nerves?
The oculomotor, trochlear, and abducens nerves control actions of the intraocular (pupillary sphincter) and extraocular muscles. These nerves are observed for symmetry of eye movement, globe position, asymmetry or drooping of the eyelid (ptosis), and twitching or fluttering of the lids or globes.
What is the strongest muscle in the human body?
The strongest muscle based on its weight is the masseter. With all muscles of the jaw working together it can close the teeth with a force as great as 55 pounds (25 kilograms) on the incisors or 200 pounds (90.7 kilograms) on the molars.
