The skin is the largest organ in the human body as most of us carry about 8 pounds and 22 square feet of it. Our flesh covering does more than just give us an identity — it protects our organs, sheds cells, and keep us either cool or war. However, how much do we really know about our skin? Medical Daily has rounded up five weird facts about the body's largest organ that you probably should know.

Fact #1: There are two types of skin aging.

Our skin ages due to the natural aging process. We all get visible lines on our face, so it's natural for us to lose some of our "youthful fullness" with age. Our genes are largely in control when our skin becomes noticeably thinner and drier, known as "intrinsic aging", according to the American Academy of Dermatology.

However, our environment and lifestyle choices can lead our skin to age prematurely, known as "extrinsic aging." We can slow the effects this type of aging has on our skin by practicing healthy habits.

Fact #2: Skin is waterproof.

The skin acts as a raincoat, or barrier to water, meaning we can swim in a pool or an ocean and nothing will pass into or leave our skin. Each superficial cell is surrounded by waterproofing lipids, or fats like cholesterol, fatty acids, and ceramides that contribute to its abilities. It prevents any water from getting past in either direction — except where the skin layer is modified to form pores.  

Fact #3: Tense muscles lead to goosebumps.

The brain sends signals to our muscles when we feel cold or experience a strong emotion. The surrounding area protrudes causing both bumps on our skin and the hair on our arms and neck to stand on end that lead to the appearance of goosebumps. This physiological phenomena is inherited from our animal ancestors

Fact #4: Scratching the skin temporarily distracts the brain from the itch.

It’s known scratching blocks the itching sensation. The pain that is accompanied by scratching manages to temporarily distract the brain from the itch. These pain signals are transmitted to the brain by nerve cells just like an itchy feeling is also transmitted by another set of nerve cells.

Fact #5: The brain predicts movement, like tickling ourselves.

The brain is able to predict sensations when they're caused by our own movement, but not when someone else does it. The cerebellum — responsible for coordinating and regulating muscle activity — predicts the sensation and this prediction is used to cancel the response of other brain areas to the tickle, according to Scientific American. Although research is limited, it is known the brain is trained to process what to feel when someone moves or performs any function.