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what are ciliary muscles ???
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Answers
Answer:
the part of the eye that connects the nearest to the to write it consists of the ciliary muscle which alters the curvature of the lens a series of radial sineri process from which the lens is suspended by ligaments and the salary ring which joins the choroid.
Explanation:
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Answer:
hey mate:-
Explanation:
The ciliary muscle is a ring of smooth muscle in the eye's middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humor into Schlemm's canal. It changes the shape of the lens within the eye, not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae.
Development Edit
The ciliary muscle develops from mesenchyme within the choroid and is considered a cranial neural crest derivative.
Ciliary ganglion with parasympathetic fibers of ciliary nerves.
The ciliary muscle receives parasympathetic fibers from the short ciliary nerves that arise from the ciliary ganglion. The sympathetic postganglionic fibers are part of cranial nerve V1 (Nasociliary nerve of the trigeminal), while presynaptic parasympathetic fibers to the ciliary ganglia are from the oculomotor nerve. The postganglionic sympathetic innervation arises from the superior cervical ganglia.
Presynaptic parasympathetic signals that originate in the Edinger-Westphal nucleus are carried by cranial nerve III (the oculomotor nerve) and travel through the ciliary ganglion via the postganglionic parasympathetics fibers which travel in the short ciliary nerves and supply the ciliary body and iris. Parasympathetic activation of the M3 muscarinic receptors causes ciliary muscle contraction, the effect of contraction is to decrease the diameter of the ring of ciliary muscle (causing constriction of the pupil and accommodation). The zonule fibers relax and the lens becomes more spherical, increasing its power to refract light for near vision.[citation needed]
The parasympathetic tone is dominant when a higher degree of accommodation of the lens is required, such as reading a book.
- FUNCTION:-
The ciliary fibers have circular (Ivanoff)longitudinal (meridional) and radial orientations.
longitudinal (meridional) and radial orientations.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. 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. Conversely, relaxation of the ciliary muscle causes the zonular fibers to become taut, flattening the lens, increasing the focal distance,increasing long range focus. Although Helmholtz's theory has been widely accepted since 1855, its mechanism still remains controversial. Alternative theories of accommodation have been proposed by others, including L. Johnson, M. Tscherning, and especially Ronald A. Schachar.
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