Account for the hill-and-valley design of the skin. Please explain what it is too.

Answer 1

Hello!

Under the epidermis (the outermost layer of the skin) sits the dermis, a fleshy layer that includes capillaries, ducts, and nerves. The top layer of the dermis is called the papillary layer because it contains many papillae, or peg-like projections. These papillae contain receptors like the Meissner's corpuscle that senses change in texture, and serve to increase the surface area of the skin, especially in the fingertips. Their ridge-like form leads to the hill-and-valley appearance of the skin.

This is not the most basic explanation, so let me know if you have follow-up questions!

Answer 2

Hi Wine. I've seen this question sitting unanswered for too long. So here is what I can tell you.

The skin is the largest organ in the body and it has multiple functions: sensory perception (touch), protection (physical barrier), excretion (sweating), temperature control (sweating again and surface area).

Your questions asks about the hill-and-valley design of the skin. The skin on some parts of the body doesn't show this quite as obviously, like the face or stomach or ears. Probably the best place to see this is on the back of your hand. Think of your skin as being like a sheet stretched over a mattress; if the mattress is lumpy or pillow-topped then the sheet has hills and valleys, if the mattress is smooth underneath, so is the sheet.

Remember too that this sheet has to allow for movement.

So the appearance of the epidermis on your hand comes from several factors:

1. the structure of the underlying tissues plays a big role: your hand is a pretty busy place, lots of blood vessels, pores and nerves under the skin.
2. the need to have some slack to allow for free movement; look at the skin on your knuckles to find larger folds, open and close your fist to see how the hill-and-valley folds change appearance.
3. the folds (no matter how small) increase the total surface area for excretion, sensory input and temperature control.

Hope this helps.