What is the annulus of Zinn?
What is 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.
What structures 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.
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.
Which structure passes through the tendinous ring of the orbit?
The area enclosed by the tendinous ring is called the oculomotor foramen, and several blood vessels and nerves pass through the foramen, having entered the orbit either through the optic canal or the superior orbital fissure (see Figure 10-8).
Which muscle is supplied by Trochlear nerve?
the superior oblique muscle
The only muscle the trochlear nerve innervates, the superior oblique muscle, is the longest and thinnest muscle among the extraocular muscles.
Is the levator Palpebrae Superioris in extraocular muscle?
Cranial Nerves Cranial nerve III innervates four of the six extraocular muscles of the eye as well as the levator palpebrae superioris muscle of the eyelid and, via projections to the ciliary ganglion, the small intraocular muscles that control the constriction of the pupil and the shape of the lens.
What pass through superior orbital fissure?
This fissure, which separates the greater and lesser wings of the sphenoid and lies between the optic foramen and the foramen rotundum, provides passage to the three motor nerves to the extraocular muscles of the orbit: oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN VI).
What blood vessel passes through superior orbital fissure?
Lateral part transmits: superior ophthalmic vein, lacrimal nerve, frontal nerve, trochlear nerve (CN IV), recurrent meningeal branch of lacrimal artery (anastomotic branch of lacrimal artery with the middle meningeal artery)
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.
What nerves go through common tendinous ring?
The tendinous ring straddles the lower, medial part of the superior orbital fissure….Through it (from superior to inferior) pass:
- 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 causes damage to the trochlear nerve?
In some people, it’s congenital, meaning they are born with this condition. It may also be due to trauma from rapid head movements, like during motor vehicle accidents. The trochlear nerve is one of the more fragile cranial nerves because it’s thin and long. Cranial nerve palsy sometimes occurs after minor injuries.
How do you treat trochlear nerve damage?
Treatment of trochlear nerve palsy is nearly exclusively surgical. Prisms are rarely helpful due to incomitance of vertical deviation and since they are not suitable to correct for cyclodeviation. Surgery should be scheduled not earlier than 12 months after onset of the palsy.
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 ( extraocular muscles ).
What is the difference between anulus tendineus communis and rectus inferioris?
Some sources distinguish between these terms more precisely, with the anulus tendineus communis being the parent structure, divided into two parts: a lower, the ligament or tendon of Zinn, which gives origin to the rectus inferior, part of the rectus internus, and the lower head of origin of the rectus lateralis.
What is the function of the tendinous ring?
It can be used to divide the regions of the superior orbital fissure. The arteries surrounding the optic nerve are sometimes called the “circle of Zinn-Haller” (“CZH”). This vascular structure is also sometimes called “circle of Zinn”. The following structures pass through the tendinous ring (superior to inferior):
What is the function of the circle of Zinn Haller?
It is the common origin of the four rectus muscles of the group of extraocular muscles . It can be used to divide the regions of the superior orbital fissure. The arteries surrounding the optic nerve are sometimes called the “circle of Zinn-Haller” (“CZH”).