Human anatomy and physiology sem 1 (unit4) hand written notes pdf

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The human eye is a complex and sensitive organ responsible for vision. It is a spherical shaped structure, about the size of a ping-pong ball, with a diameter of approximately 24mm. It is located in the eye socket, which is protected by bones for safety.

The eye is composed of several parts, including the sclera, iris, pupil, cornea, lens, retina and optic nerve. The outermost layer, the sclera, is a white, tough and fibrous membrane that provides the eyeball with its shape, structure and strength. The iris is a colorful, circular muscle that controls the size of the pupil, and the pupil is the black hole at the center that lets light enter.

The cornea is a transparent, dome-shaped front part of the eye that refracts (bends) light into the eye, allowing it to focus on objects. The lens, located behind the iris, further refracts the light to help form a clear and focused image onto the retina. The retina is a layer of light-sensitive cells that line the back of the eye, and it converts the light into electric signals that are sent to the brain through the optic nerve.

The eye is also equipped with various protective mechanisms and structures, such as the eyelids, eyelashes, and tears that help to keep the eye moist, clean and free from debris. These protective mechanisms work together to keep the eye healthy and functioning properly.

Overall, the human eye is a highly sophisticated and complex organ that plays a crucial role in our day-to-day lives by providing us vision, which allows us to navigate our surroundings, recognize faces and objects, read, and focus on fine details.