Is constrictor pupillae a smooth muscle?

The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris….

What muscles are responsible for pupil constriction?

The iris sphincter muscle receives its parasympathetic innervation via the short ciliary nerves which lead to pupillary constriction (miosis) and accommodation. [3] The parasympathetic fibers that serve the sphincter muscle originate from the Edinger-Westphal nucleus of cranial nerve III.

What does the dilator Pupillae muscle do?

dilator muscle, any of the muscles that widen a body part. In humans, the dilator muscle of the iris contains fibres that extend radially through the iris of the eye and involuntarily contract as available light decreases, thus dilating the pupil.

What is the innervation of constrictor and dilator Pupillae?

The dilator pupillae muscle is innervated by non-myelinated sympathetic fibres whose cell bodies are situated in the superior cervical sympathetic ganglion. Its parasympathetic innervation seems less significant. The dilator pupillae extends only as far centrally as the outer margin of the sphincter pupillae.

What muscles cause the dilation of the pupil?

The iris dilator muscle has fibers arranged radially from the sphincter to the ciliary border, receives sympathetic innervation, and functions to cause dilation of the pupil (mydriasis).

What muscle tissue that dilates and constricts the pupils of your eyes?

The iris consists of two sheets of smooth muscle with contrary actions: dilation (expansion) and contraction (constriction). These muscles control the size of the pupil and thus determine how much light reaches the sensory tissue of the retina.

What is the function of the sphincter Pupillae and dilator pupillae?

In these reflexes, sphincter pupillae constricts the pupil (miosis), while dilator pupillae dilates it (midriasis).

Is sphincter pupillae a smooth muscle?

As does cardiac muscle, much of the smooth muscle in the body arises from splanchnic mesoderm. Exceptions are the ciliary muscle and sphincter pupillae muscles of the eye, which are derived from neural crest ectoderm, and much of the vascular smooth muscle, which frequently arises from the local mesoderm.

What type of muscle is sphincter pupillae?

circular muscle
Sphincter pupillae is a circular muscle, about 1 millimeter wide. It is located in the pupillary zone of stromal layer of the iris, attaching to and encircling the pupillary margin of iris.

What is ora serrata in human eye?

The ora serrata is the peripheral termination of the retina and lies approximately 5 mm anterior to the equator of the eye. The ora serrata is approximately 2 mm wide and is the site of transition from the complex, multilayered neural retina to the single, nonpigmented layer of ciliary epithelium.