ciliary

The Ciliary Body

The visual system of our body comprises sensory organs called the eyes and the central nervous system. The eye is a vital and sensitive organ that receives images from our surroundings and sends signals to the brain. The brain helps interpret these signals to construct the images we see. The eyeball has the following parts:

• Cornea
• Sclera
• Pupil
• Iris
• Conjunctiva glands
• Lacrimal glands
• Lens
• Retina
• Ciliary Body
• Choroid
• Vitreous Humour
• Aqueous Humour

Definition of Ciliary

The ciliary is the inner structure of the eyeball that consists of the ciliary muscle, ciliary epithelium, ciliary processes and ciliary vessels. The ciliary muscle is a circular muscle that is an extension of the iris, the coloured portion of the eye. This muscle lies behind the iris. It is part of the uvea, which is the layer of the eye that provides nutrients and oxygen to the tissue. The main task of the muscles is to adjust the shape of the lens inside the eye, which in turn helps the eye focus on a certain object. The clear fluid that fills the space between the iris and cornea, vitreous humour, is produced by the ciliary muscle. The ciliary body connects the root of the iris to the ora serrata.

Anatomy

The ciliary is connected to the lens by several tiny fibrous tissue chords called zonular fibres. These fibres aid the process of the lens changing shape. This is done to view a distant object or focus on a minuscule detail— a crucial eye function. The process of adjustment of the lens is called accommodation. This function requires a well-oriented system, providing it with oxygen and nutrients brought by the ophthalmic artery.

 Ciliary Classification

The ciliary body is found between the front portion of the choroid and the iris of the eye. It is ring-shaped and is in the shape of a triangle, with the base of the triangle being adjacent to the iris. The choroid, iris, and ciliary body together form the uveal tract. The uveal tract connects the outer layer (sclera) and the inner layer (retina).

The ciliary classification can be broadly done with the following main structure:

● Ciliary Muscle

The largest part of the ciliary body is known as the ciliary muscle. This is a smooth structure of the inner eye that plays a vital role in the focusing of our eyes. When the ciliary muscle contracts, it helps loosen the zonules of the suspensory ligaments that alter the refraction of the lens by stretching it, which makes the lens convex in shape; this is the process of accommodation reflex. The dilation and contraction of the pupil also take place with a combination of the pupillae dilator and sphincter pupillae, which is also a muscle.

● Ciliary Processes

The protrusions in the ciliary body—small, thin projections—are known as the ciliary processes. Protrusions such as these connect the zonular fibres and the lens, facilitating the contraction and dilation of the lens. In addition, the aqueous humour is secreted by these processes, as they contain the epithelium.

 ● Ciliary Epithelium

The ciliary epithelium is bilayered. The entire surface of the ciliary body is covered in a specialised epithelium made up of two types of epithelial cells. This phenomenon is not found anywhere else in the body. For example, there are only monolayers of epithelial cells in the lungs, or multiple layers of a single cell, like the corneal epithelial cells. The function of the ciliary epithelial is to form a barrier between the different compartments of the eye.

Supply of Blood

The ciliary muscles contract to move the anchoring point of the zonules slightly inwards. This helps relax the tension on the zonule, and with the help of the natural elasticity, the lens acquires a more rounded (convex) shape. This is how the eye’s focus is shifted. The muscular motion requires a steady supply of blood, oxygen and nutrients. As a result, the surface of the ciliary body is covered with ridges called processes. These processes are laden with fine pipework of blood vessels.

Nerves related to ciliary

The main nerves that transmit signals into the brain are the parasympathetic fibres. The preganglionic fibres come from the nucleus called the Edinger-Westphal, which lies in the midbrain and is connected to the ciliary body. The parasympathetic fibres are connected to the ciliary ganglion, neurotransmitters for the cilia body.

Conclusion

The ciliary body carries out a number of important functions in the body. However, the most important task relates to the reflex accommodation that helps focus images. In this task, there are a number of complex anatomical structures that facilitate the functioning of the ciliary body. There are specially designed muscles that change the lens and its refractive index, thus helping the eye focus on objects near and far. The blood supply of the ciliary body is well regulated by the specially assigned blood vessels. Moreover, since vision is such an important function of the body, there are nerves that work specifically for transmitting and translating visual stimuli.