The Part of Human Body that lack Blood supply


Dear my readers, how are you?, mine I'm fine. Today I come with something that other people might ask themselves, Is there any part of human body that lack blood supply? Is it possible?, how does it survive? as we know that nutrients and air come from the blood.

After finding out the truth from various sources now I come with an answer, that part of the human body that lack blood supply is the CORNEA OF THE EYE



The following explanations including the anatomy of the eye reveals the truth;

The Cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power. The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid.

Together with the lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power.   In humans, the refractive power of the cornea is approximately 43 dioptres.

CORNEAL ANATOMY
In humans, the cornea has a diameter of about 11.5 mm and a thickness of 500-600 μm in the center and 600800 μm at the periphery. Transparency, avascularity, the presence of immature resident immune cells, and immunologic privilege makes the cornea a very special tissue. The cornea has five layers. From the front to the back, as follows;

1. Corneal epithelium
2. Bowman's layer
3. Corneal stroma
4. Descemet's membrane
5. Corneal endothelium



1. The corneal epithelium
Is the outer layer of the cornea, has five to seven cells thick and measures about 50 microns, making it slightly less than 10 percent of the thickness of the entire cornea. Epithelial cells are constantly being produced and sloughed off in the tear layer of the surface of the eye. The turnover time for the entire corneal epithelium is about one week.

2. Bowman's layer
It is very thin layer about 8 to 14 microns and dense fibrous sheet of connective tissue that forms the transition between the corneal epithelium and the underlying stroma.

3. The corneal stroma
Is the middle layer of the cornea, has approximately 500 microns thick, or about 90 percent of the thickness of the overall cornea. It is composed of strands of connective tissue called collagen fibrils. These fibrils are uniform in size and are arranged parallel to the cornea surface in 200 to 300 flat bundles called lamellae that extend across the entire cornea. The regular arrangement and uniform spacing of these lamellae is what enables the cornea to be perfectly clear.

4. Descemet's membrane
It is very thin layer that separates the stroma from the underlying endothelial layer of the cornea. Descemet's membrane gradually thickens throughout life it's about 5 microns thick in children and 15 microns thick in adults.

5. The corneal endothelium
Is the innermost layer of the cornea. The back of the endothelium is bathed in the clear aqueous humor that fills the space between the cornea and the iris and pupil. The corneal endothelium is only a single layer of cells thick and measures about 5 microns. Most of the endothelial cells are hexagonal (six-sided), but some may have five or seven sides. The regular arrangement of these cells is sometimes called the endothelial mosaic.

TRUTH
The clear cornea allows light to enter the eye for vision. But it has another very important function as well the cornea provides approximately 65 to 75 percent of the focusing power of the eye.

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Because transparency is of prime importance the cornea does not have blood vessels; it receives nutrients via diffusion from the tear fluid at the outside and the aqueous humour at the inside and also from neurotrophins supplied by nerve fibers that innervate it.

The cornea is the only part of a human body that has no blood supply; it gets oxygen directly through the air. The cornea is the fastest healing tissue in the human body, thus, most corneal abrasions will heal within 24-36 hours.

That's all about cornea and its Interesting facts, Stay tuned for more other best posts. I you want to share your experience about this article, you are free to leave your comment below.

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Posted by: Lusubilo A. Mwaijengo

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