The structure of the eye is an important topic to understand as one of the important sensory organs in the human body. It is mainly responsible for vision, differentiation of colour, and maintaining the biological clock of the human body. The human eye can be compared to a camera as both works by gathering, focusing, and transmitting the light through the lens for creating an image of an object.
Functions of the Human Eye
The human eyes are the most complicated sense organs in the human body. From the muscles and tissues to nerves and blood vessels, every part of the human eye is responsible for a certain action. Furthermore, contrary to popular belief, the eye is not perfectly spherical; instead, it is two separate segments fused together. It is made up of several muscles and tissues that come together to form a roughly spherical structure. From an anatomical perspective, the human eye can be broadly classified into the external structure and internal structure.
External Structure of an Eye
The parts of the eye that are visible externally include the following:-
- Sclera: It is a white visible portion. It is made up of dense connective tissue and protects the inner parts.
- Conjunctiva: It lines the sclera and made up of stratified squamous epithelium. It keeps our eyes moist and clear and provides lubrication by secreting mucus and tears.
- Cornea: It is the transparent, anterior or front part of our eye, which covers the pupil and the iris. The main function is to refract the light along with the lens.
- Iris: It is the pigmented, coloured portion of the eye, visible externally. The main function of the iris is to control the diameter of the pupil according to the light source.
- Pupil: It is the small aperture located in the centre of the Iris. It allows light to enter and focus on the retina.
- Lens: It is a transparent, biconvex, lens of an eye. The lens is attached to the ciliary body by ligaments. The lens along with cornea refracts light so that it focuses on the retina.
- Retina: It is the innermost layer of the eye. It is light sensitive and acts as a film of a camera. Three layers of neural cells are present in them, they are ganglion, bipolar and photoreceptor cells. It converts the image into electrical nerve impulses for the visual perception by the brain.
- Optic nerve: It is located at the posterior portion of the eyes. The optic nerves carry all the nerve impulses from the retina to the human brain for perception.
- Aqueous Humour: It is a watery fluid present between the cornea and the lens. It nourishes the eye and keeps it inflated.
- Vitreous Humour: it is a transparent, jelly-like substance present between the lens and the retina. It contains water (99%), collage, proteins, etc. The main function of vitreous humour is to protect eyes and maintain its spherical shape.
The internal components of the eye include:
- Aqueous humour
- Optic nerve
- Vitreous humour