The common tendinous ring, also known as the annulus of Zinn, or annular tendon, 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
recti muscles of the group of
extraocular muscles.
It can be used to divide the regions of the
superior orbital fissure
The superior orbital fissure is a foramen or cleft of the skull between the lesser and greater wings of the sphenoid bone. It gives passage to multiple structures, including the oculomotor nerve, trochlear nerve, ophthalmic nerve, abducens ner ...
.
The
arteries surrounding the optic nerve form a vascular structure known as the
circle of Zinn-Haller
The short posterior ciliary arteries, around twenty in number, arise from the medial posterior ciliary artery and lateral posterior ciliary artery, which are branches of the ophthalmic artery as it crosses the optic nerve.
Course and target
They p ...
, or sometimes as the ''circle of Zinn''.
The following structures pass through the tendinous ring (superior to inferior):
* Superior division of the
oculomotor nerve
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...
(CNIII)
*
Nasociliary nerve (branch of
ophthalmic nerve)
* Inferior division of the
oculomotor nerve
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...
(CNIII)
*
Abducens nerve (CNVI)
* Optic nerve
Parts
The common tendinous ring spans the
superior orbital fissure
The superior orbital fissure is a foramen or cleft of the skull between the lesser and greater wings of the sphenoid bone. It gives passage to multiple structures, including the oculomotor nerve, trochlear nerve, ophthalmic nerve, abducens ner ...
and can be described as having two parts – an inferior tendon which gives origin to the inferior rectus muscle, and to part of the lateral rectus muscle; and a superior tendon which gives origin to the superior rectus muscle, and to part of the medial and lateral recti muscles.
Eponym
It is named for
Johann Gottfried Zinn.
[J. G. Zinn. Descriptio anatomica oculi humani. Göttingen, B. Abrami Vandenhoeck, 1755.] It should not be confused with the
zonule of Zinn, though it is named after the same person.
References
{{Authority control
Histology
Human eye anatomy