part of smooth muscle cell ciliary muscle cell Ciliary muscle cells are specialized contractile cells that constitute the ciliary muscle, a component of the eye in vertebrates. These cells form a ring around the iris, the eye's colored part. Ciliary muscle cells fall into the category of smooth muscle cells, characterized by their lack of the striations typical of skeletal and cardiac muscle cells. Their shape is elongated and pointed at both ends, and they occur in multi-nucleated syncytia where many cells share the same cytoplasm. Ciliary muscle cells primarily control the eye's accommodation, adjusting the thickness and curvature of the lens to fine-tune the focus of light on the retina. When ciliary muscle cells contract, tension on the zonular fibers holding the lens in place is reduced, allowing the lens to become thicker and increase its refractive power. Conversely, when the ciliary muscle cells relax, the tension on the zonular fibers increases, causing the lens to become flatter and decrease its refractive power. This adjustment facilitates clear vision at different distances, ranging from near to far objects. Additionally, ciliary muscle cells play a role in draining the eye's aqueous humor, which is the clear fluid that fills the anterior chamber of the eye between the cornea and the lens. By controlling the shape of the surrounding trabecular meshwork through muscle contractions and relaxations, ciliary muscle cells indirectly regulate intraocular pressure, a factor critical for preventing ocular conditions like glaucoma. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) smooth muscle cell of ciliary body https://cellxgene.cziscience.com/cellguide/CL_1000443 FMA:70610 A smooth muscle cell that is part of the ciliary body. ciliary body