The Skin or ("Hey! Your epidermis is showing!")
Hey! Your epidermis is showing! What is the epidermis, anyway? The epidermis is the outside layer of your skin. The dermis is the inside layer of skin. The skin, all 6-10 lb. (~3-4 kg) and 20 square feet in an adult, is a giant, washable, stretchable, tough, water-proof sensory apparatus covering your whole body. It keeps your insides in!

Actually, there are four different types of skin:

  1. Mucocutaneous: at the junction of the mucous membrane, hairy skin, lips, and tongue.
  2. Mucous membrane: lining the inside of body orifices.
  3. Glabrous: skin without hair.
  4. Hairy: skin with hair.

Glabrous skin has an epidermal layer of about 1.5 mm in thickness and a dermis of about 3 mm. Hairy skin has an epidermal layer of 0.07 mm in thickness and a dermis of about 1-2 mm.

Skin Receptors
Receptor EndingNerve FiberFunctionLocation

Hair Follicle Ending
A-betaResponds to hair displacement.Wraps around hair follicle in, of course, hairy skin.

Ruffini Endings
A-betaResponds to pressure on skin.Dermis of both hairy and glabrous skin.

Krause corpuscle
A-betaResponds to pressure.Lips, tongue, and genitals.

Pacinian corpuscle
A-betaResponds to vibration. Most sensitive in 150-300 Hz rangeDeep layers of dermis in both hairy and glabrous skin.

Meissner corpuscle
A-betaResponds to vibration. Most sensitive in 20-40 Hz rangeDermis of glabrous skin.

Free nerve endings
A-delta and CDifferent types of free nerve endings that respond to mechanical, thermal or noxious stimulation. Various types are found throughout the skin.
Merkel CellsA-betaResponds to pressure of the skin.Epidermis of glabrous skin.

Nerve fibers that are attached to different types of skin receptors either continue to discharge during a stimulus ("slowly-adapting") or respond only when the stimulus starts and sometimes when a stimulus ends ("rapidly-adapting"). In other words, slowly-adapting nerve fibers send information about ongoing stimulation; rapidly-adapting nerve fibers send information related to changing stimuli. The Pacinian corpuscle receptor is a classic example of a rapidly-adapting type receptor. The Ruffini nerve ending is a slowly-adapting type receptor.

Did you know?

  • We lose about 50 million skin cells each day!

  • The eyelid has the thinnest skin on the entire body. (Source: Sims, M., Adam's Navel, New York: Viking, 2003)

Try it!

Play the Interactive Word Search Game on Touch.

Use the Lesson Plan on Two Point Discrimination.

Links of interest:

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