What is the Only Part of the Body That Doesn't Need Blood?

You will be surprised to know that cornea is the only living tissue in the human body that does not require blood circulation. In fact, the oxygen and nutrients that are required for its proper functioning are directly supplied from the tear fluid and aqueous humor. However, we cannot deny the fact that blood circulation in the body, including eye blood supply, is extremely important.

The circulatory system comprises arteries and veins that carry blood from and towards the heart. Arteries carry blood from the heart and veins carry the blood back to the heart. The circulatory system supplies oxygen to all the cells in the body and expels carbon dioxide.

Eye blood supply and more about ‘cornea’ of the human eye

The cornea in the human eye is the transparent part of the eye and the only living tissue in the body that does not require any blood supply.

The cornea delivers the eye’s optical power. It covers the iris (colored part of the eyes), the pupil (a hole located at the center of the iris) and the anterior chamber (the space behind the cornea that is filled with a watery fluid). The part of the eye is so sensitive that even if you try to touch it, it automatically closes the eyelid. The cornea is also sensitive to temperature and foreign particles.

Unlike most tissues in the human body, the cornea is one of the few body parts that does not have any blood vessels. The main function of the cornea is to direct the light that enters the eyes. Blood vessels in the cornea may prevent light from entering, in turn, affecting the vision.

In the absence of blood vessels, the nutrients are provided to the cornea with the help of tears and the watery fluid that is present in the anterior chamber.

Layers of the cornea of the human eye

The cornea is approximately 550 microns thick and comprises five layers, each having different functions.

The five layers of the cornea are:

• Epithelium
• Bowman’s layer
• Stroma
• Descemet’s membrane
• Endothelium

Epithelium

The epithelium is the outermost layer of the cornea. It works as a barrier and prevents the loss of fluids in the form of tears. It also prevents foreign particles from entering the epithelium and corneal stroma.

Bowman’s layer

The Bowman’s layer, also known as Bowman’s membrane, is the layer of the cornea that is located between epithelium and stroma. The function of Bowman’s layer is not clear. Though, it is assumed that the layer protects the subepithelial nerve plexus and helps in sensory recovery.

Stroma

The stroma of the cornea, also known as substantia propria, is the thickest layer of the cornea located in between the epithelium and the inner endothelium. The fibrous, thick, and tough layer comprises a major part of the cornea. It plays a significant role when it comes to vision function.

The main function of the stroma is to maintain transparency and to support normal corneal development.

Descemet’s membrane

The Descemet’s membrane consists of two distinct layers and helps to preserve phenotype and proper functioning of corneal endothelial cells.

Endothelium

It is a single layer of delicate cells that helps to control hydration in the human eye.

Fun fact: The cornea is the tissue in the human body that heals within 24 to 36 hours.

What happens when you wear contact lenses?

Contact lenses have the property to make your eyes dry further causing itchiness, irritation, and redness. The lens absorbs most of the tears on the eyes to keep itself soft and hence reduces the number of tears on the cornea.

Tips to take good care of eyes

Symptoms of eye issues

If you experience any issues with your eyes, be it a change in the vision or itching in the eyes, contact your eye care professional. Get your eye examination done.

Some of the symptoms to look out for are painful eyes, double vision, itching in eyes, trouble seeing at night, blurry vision, partial vision loss, etc.

Consume a healthy diet

For good eye health, it is important to consume a healthy diet. Make sure your diet comprises essential nutrients like lutein, zinc, vitamin C, and omega-3 fatty acids.

A good meal also helps to ward off other health conditions. These include obesity and diabetes that are also the cause of a number of eye conditions. Eat a lot of green leafy vegetables, oily fish, eggs, beans, nuts, oysters, and fruits.

Quit smoking

Avoid smoking. It damages your optic nerve that increases your chances of getting cataracts.

Protect your eyes from UV rays

Protect your eyes from the harmful sun rays. Wear sunglasses that will protect your eyes from the sun’s ultraviolet rays. Excess exposure to the rays causes a number of eye issues including cataracts and macular degeneration.

Wear safety glasses at work

If your work demands coming in contact with airborne materials, make sure you protect your eyes with the help of safety glasses.

Blink at regular intervals

If your work demands staring at a computer/laptop screen for long hours, it can cause dry eyes and blurry vision. Use an anti-glare screen. Make sure you blink your eyes often and take a break at regular intervals.

Get an eye checkup done

Visit your ophthalmologist at regular intervals. Get your eye checkup done and understand if your glasses and lenses are up to date. If you have a family history of eye issues, consult your doctor.

Use the 20-20-20 rule

If your work demands staring at the screen for long hours, use the 20-20-20 rule. It means after every 20 minutes, look at objects that are 20 feet away from you for a period of 20 seconds.

Now that you know why the cornea of the human eye doesn’t require blood, let’s share with you a fun fact about other parts of the body that do not require blood.

Fun fact: Hair, nails, tooth enamel, and skin layers are the other body parts that do not require blood circulation.

Learn more about overall eye health here.