Overview

I asked ten friends to list about 10 to 20 random parts of the body, and the usuals were the eye, ear, nose, and some internal organs like the brain, kidneys and intestines. Only one person mentioned the eyelids. And you probably know why. 

Unconsciously, we see some parts of the body as more important than others, but actually, every part of the body is useful in one way or another and without them, life would definitely not be the same. One of these ‘underrated’ parts of the body is the eyelids. 

In this article, we’ll look at the functions of the eyelids and understand their importance. 

The Eyelids

The eyelids are thin layers or folds of skin that close over the eye to protect it. Everyone has upper and lower eyelids housing the muscles that make it possible for us to open and close our eyes, either voluntarily or involuntarily.

The eyelids stretch when our eyes are closed to cover the eyes and ‘fold’ up when our eyes are open.

Functions of Eyelids

As ‘insignificant’ the eyelids may seem, any damage will leave the eyes unprotected from impacts, harsh UV rays, infections, or lead to impaired sight. For this reason, the eyelids are one of the most vital components of the Human Visual System.

The skin, muscles, glands, nerves and other tissues that make up the eyelids have their parts to play in keeping the eyes mobile, lubricated and protected. Most times, the eyelids cannot prevent every other risk, so extra eye protection is advised for some activities or professions.

Eyelashes

The eyelashes are short hairs that grow out from the eyelids. Asides from the cosmetic importance of eyelashes, those tiny hairs form the first line of defence for the eyes. 

Your eyelashes will do the following:

  • Keep water and sweat from entering your eyes.
  • Trigger a reflex to close your eyes when hazards are in close range.
  • Capture debris, dust particles and other pollutants, keeping them out of the eyes.
  • Maintain the lubrication in the eyes.
  • Add an extra layer of defence when the eyelids are closed.

Skin

A thin layer of skin makes up the outer layer of the upper and lower eyelids and covers the eyelids. It protects the muscles, nerves and glands beneath from infections and injuries.

If you try to feel the skin on your eyelids, you’ll figure out it is lighter than other parts of your body - because it has lower amounts of keratin, as well as little or no fat in the subcutaneous layer. 

Because of this particular feature, the skin is vulnerable to swellings, e.g. boils and abrasions.

Conjunctiva

The conjunctiva is an invisible and thin layer of clear tissue that aids the lubrication of the eyes. It is also called the mucous membrane, and it covers,

  • the sclera (the white part of the eye),
  • the inner part of the eyelids.

The conjunctiva secretes fluids to keep the eye moist and protect it from foreign substances and pollutants. It also contributes to the tear film, a thin layer of fluid that coats and lubricates the surface of the eyeball.

The essence of moisture in the eyes is to keep the eye surface healthy and mobile, preventing eye strain and itchy eyes.

Muscles

Beneath the eyelids are several muscles or groups of muscles that are principally for the functioning of the eyelids, opening and closing the eyes. The levator, muller’s and frontalis muscles are important for blinking and holding the upper eyelids in their normal position. Every time you blink, a slight pumping or squeezing mechanism occurs which spreads small amounts of tears over your eyes. Other muscles in the eyelids are also responsible for, 

  • winking
  • keeping the eyes closed during sleep
  • the flow of tears through the tear ducts to maintain moisture

The muscles in the upper eyelids function quite differently from those in the lower eyelids but they work together to perform one function, which is the opening and closing of the eyelids. 

Tarsus

The tarsus is a tough, dense connective tissue, similar to the tendons attaching muscles to bones, that holds the eyelids together and gives them shape. It is responsible for the natural contour of your eyelids, and the eyelashes all grow from its top and lower parts.

The Tarsis are living tissue structures that reside beneath the skin of the eyelid, almost like a frame. The skin of the eyelids wraps around this floor, which is firm enough to give the eyelids shape.

The tarsus also houses glands essential to the visual system's operation. Now, let's look at glands.

Glands

Glands are small organs that secrete substances that help the body run smoothly and function effectively. 

When we talk about the lubricative function of the eyelids, it's the work of the glands present. The glands in the eyelids include sebaceous glands, sweat glands, tear glands, and meibomian glands

The meibomian glands in the tarsus secrete oils to lubricate the surface of the eye and help prevent the evaporation of tears.

The sebaceous and sweats glands in the eyelids also secrete oil around the follicles of the eyelashes and excrete sweat.

The tear glands also called the lacrimal glands that produce our lubricating tears, are small and spread throughout the eyelid releasing tears into the eye socket and the eye’s surface. 

The lacrimal gland, which is positioned beneath the upper eyelid and the body orbit, secretes reflex tears. When you get emotional from a movie or heartbreak, it's this gland that causes you to cry. When foreign particles find their way into the eyes, these reflex tears are secreted to wash away the particles. 

Have you ever tried to understand why your crying is always accompanied by a running nose? It is because the tear ducts carry excess tears to the nasal cavity. Surprised?

Nerves

When the nerves responsible for receiving stimuli and bringing responses from the brain in a particular part of the body are damaged, that part of the body is pretty much useless.

The same goes for the eyelids. We have looked at the various functions of the eyelids, so it is safe to say that it takes a lot of nerves to ensure the proper functioning of the eyelids as they direct the movement of the eyelids and provide sensation.

Conclusion

The eyelids are situated in a position where it is prone to injuries and damage. Understanding the functions and importance of your eyelids should help you take better care of your eyes and ensure you are not exposing yourself to unnecessary hazards. 

Remember, the eyes are the windows to your body, you don’t want to live in a dark room.

Written By:
Shalom Ngbala-Okpab
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Further Reading