Intrinsic ocular muscles
or intraocular muscles
[{{cite book , last1=Ludwig , first1=Parker E. , last2=Aslam , first2=Sanah , last3=Czyz , first3=Craig N. , title=StatPearls , date=2024 , publisher=StatPearls Publishing , chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK470534/ , chapter=Anatomy, Head and Neck: Eye Muscles , pmid=29262013 ] are muscles of the inside of the eye structure.
The intraocular muscles are responsible for adjusting the shape of the lens and the size of the pupil. They're different from the
extraocular muscles that are outside of the eye and control the external movement of the eye.
There are three intrisic ocular muscles: the
ciliary muscle
The ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscleSchachar, Ronald A. (2012). "Anatomy and Physiology." (Chapter 4) . in the eye's middle layer, the uvea ( vascular layer). It controls accommodation for vie ...
,
pupillary sphincter muscle (
sphincter pupillae) and
pupillary dilator muscle (
dilator pupillae
The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. The pupillary dilator consists of a spokelike ...
).
All of them are
smooth muscle
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called bec ...
s.
The ciliary muscle is attached to the
zonular fibers and the zonular fibers are the suspensory ligaments of the lens.
The ciliary muscle controls
accommodation by altering the shape of the lens to be able to see an object from near to far.
The pupillary sphincter muscle and pupillary dilator muscle control the
iris to adjust the size of the
pupil
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black becau ...
to adjust how much light enters into the eye. The pupillary dilator muscle increases the pupillary diameter and it is arranged radially, but the pupillary sphincter muscle is responsible for the constriction of the pupil's diameter and it encircles the pupil.
The pupillary dilation is also called
mydriasis
Mydriasis is the Pupillary dilation, dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, Physical trauma, trauma, or the use of c ...
, and the constriction of the pupil is also called
.
See also
*
Extraocular muscle
References
Muscles of the head and neck
Human eye anatomy