What is the function of ciliary muscle and zonular fibers?

What is the function of ciliary muscle and zonular fibers?

According to Hermann von Helmholtz’s theory, the circular ciliary muscle fibers affect zonular fibers in the eye (fibers that suspend the lens in position during accommodation), enabling changes in lens shape for light focusing.

What is the ciliary muscle composed of?

smooth muscle fibers
The ciliary muscle is composed of smooth muscle fibers oriented in longitudinal, radial, and circular directions. Interweaving occurs between fiber bundles and from layer to layer, such that various amounts of connective tissue are found among the muscle bundles.

What does the ciliary fibers do?

The main action of ciliary muscle is changing the shape of the lens which occurs during the accommodation reflex. In addition, when contracting, the longitudinal fibers of ciliary muscle widen the iridocorneal space and canal of Schlemm which facilitates the draining of eye fluid.

What controls the ciliary muscle?

Parasympathetic Innervation to the Intraocular Muscles The iris sphincter and the ciliary muscle are controlled by the Edinger-Westphal nucleus, which is a dorsal-rostral part of the oculomotor nucleus. The third cranial nerve leaves the midbrain in the interpeduncular fossa.

What is pars plicata?

The pars plicata is the portion of the ciliary body that is responsible for producing aqueous humor, the fluid of the anterior chamber. The production of too much aqueous humor, or reabsorption that occurs too slowly, can lead to increases in the pressure within the eye.

What fibers are found in the ciliary ganglion?

The ciliary ganglion is one of four parasympathetic ganglia in the head. It is located behind the eye. Nerve fibers leave the brain and enter the ganglia. These fibers synapse (a junction between nerves where they communicate) with neurons going to the eye.

What do Zonular fibers do?

The zonular fibers anchor the the equator of the lens and adjacent anterior and posterior surface of the lens to the ciliary body and and ciliary part of the retina. The ciliary epithelial cells of the eye probably synthesize portions of the zonules.

What do ciliary muscles do?

The ciliary body produces the fluid in the eye called aqueous humor. It also contains the ciliary muscle, which changes the shape of the lens when your eyes focus on a near object. This process is called accommodation.

How does the ciliary muscle work?

When the ciliary muscle is contracted, the lens becomes more spherical – and has increased focussing power – due to a lessening of tension on the zonular fibres (a). When the ciliary muscles relax, these fibres become taut – pulling the lens out into a flatter shape, which has less focussing power (b).

What are meridional fibers?

Description. The meridional fibers (Brücke’s muscle), much the more numerous, arise from the posterior margin of the scleral spur; they run backward, and are attached to the ciliary processes and orbiculus ciliaris. One bundle, according to Waldeyer, is inserted into the sclera (the longitunal fibers).

What are Zonular Fibres collectively known as?

These fibers are sometimes collectively referred to as the suspensory ligaments of the lens, as they act like suspensory ligaments.

What is the shape of the ciliary muscle?

The Ciliary muscle ( m. ciliaris; Bowman’s muscle) consists of unstriped fibers: it forms a grayish, semitransparent, circular band, about 3 mm. broad, on the outer surface of the fore-part of the choroid. It is thickest in front, and consists mainly of two sets of fibers, meridional and circular. Longitudinal and radial fibers are also described.

What are the meridional fibers of the sclera?

The meridional fibers (Brücke’s muscle), much the more numerous, arise from the posterior margin of the scleral spur; they run backward, and are attached to the ciliary processes and orbiculus ciliaris. One bundle, according to Waldeyer, is inserted into the sclera (the longitunal fibers).

What is the difference between circular and radially oriented muscle fibers?

Deeper within the ciliary muscle and located more anteriorly toward the apex of the triangular-shaped region are the more radially oriented muscle fibers. Deeper still toward the apex of the triangular-shaped ciliary muscle are the circular muscle fibers.

What happens to the lens when the ciliary muscle contracts?

When the ciliary muscle contracts, it pulls itself forward and moves the frontal region toward the axis of the eye. This releases the tension on the lens caused by the zonular fibers (fibers that hold or flatten the lens). This release of tension of the zonular fibers causes the lens to become more spherical, adapting to short range focus.