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How big is a Skin Cell?

35 微米!

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Skin Cell

The cells on the surface of human skin are flat, dead cells called corneocytes, and each is about 35 micrometers across. A micrometer is a millionth of a meter. They are also very thin, about 1 micrometer or less, so each one is shaped like a tiny tile. Living skin cells deeper down are a different shape.

Size

The size is the width of one surface cell, seen from above. Studies describe corneocytes as about 30–50 micrometers across, with an average area of about 1,000 square micrometers. A circle with that area would be 36 micrometers wide, close to the 35 micrometers shown here.

Size varies over the body. Measured by area, cells from the cheek average about 590 square micrometers, which is the area of a circle about 27 micrometers wide. Cells from the abdomen average 1,050–1,240 square micrometers, like circles 37–40 micrometers wide. Face cells are smaller than forearm cells, and the face also replaces its outer layer about twice as fast as the forearm does.

Size comparisons

  • A red blood cell, 7–8 micrometers across, is about one-fifth the width of a 35-micrometer skin cell.
  • A human hair, 80–100 micrometers wide, is as wide as two or three surface skin cells side by side.
  • A skin cell is about 1.4 times as wide as a thou, one thousandth of an inch.
  • About 100,000 surface cells, at 1,000 square micrometers each, would cover a square 1 centimeter (0.4 inches) on a side.
  • If a surface skin cell were enlarged 10,000 times, it would be a tile 35 centimeters (14 inches) wide and at most about 1 centimeter (0.4 inches) thick.

From living cell to dead scale

The outer layer of skin, the epidermis, is made of stacked layers of cells. At its base is a single layer of box-shaped stem cells that keep dividing. The new cells are pushed up toward the surface. On the way they fill with keratin, the tough protein that also gives hair and nails their hardness, and they grow flatter.

By the time they reach the top layer, the stratum corneum, the cells are dead. This layer is usually 15–30 cells deep and about 10–20 micrometers thick. It keeps germs out, keeps water in and protects the living layers underneath from rubbing and scraping.

Cells at the surface are shed regularly and replaced by cells from below. The whole top layer is replaced in about four weeks.

Sources

宇宙的刻度 > Skin Cell
Thou
Although the word "thou" is most commonly known as being an old form of the word "you", a thou is also a unit of measurement. It is equal to one thousandth of an inch; in fact, that's where it gets its name. THOUsandth. Pretty cool.
Twip
A twip is a twentieth of a typographical point. That means that 12-point font is approximately 240 twips high. Also, TUIP can stand for "The Universe in Perspective”, an old name for the Scale of the Universe. TUIP and twip are pronounced the same.
Infrared Wavelength
Things that are extremely rare are "inf-rare". (infinitely rare). Inf-rare is also a verb, meaning "to make inf-rare". (e.g., "John inf-rared the precious food by eating the last of it.") Infrared light used to be quite common, but one day, a scientist somehow "infrared" it.
Silt Particle
According to the Udden-Wentworth scale, silt particles vary from the smallest of 1/256 mm to the largest of 1/16 mm. This silt particle to the right falls into that range quite well.
Smallest Object Visible to the Naked Eye
Just for your information, 100 micrometers is about the same as one tenth of a millimeter. Hold on... it's EXACTLY one tenth of a millimeter. Now that is so exact, it's almost scary!
Thickness of Paper
Paper is very thin. It's so thin it can give you a paper cut. You can do a lot of things with paper, including writing on it, drawing on it, and even folding it into shapes like squares and triangles and dodecahedrons and others.

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