An introduction to folds in the skin
Types of folds
Folds appear gradually on your body.
Let's distinguish three types of cutaneous folds:
• Initial vertical folds
• Usage folds
Initial vertical folds
Yes, the body of a newborn baby is already very folded with initial and usage folds.
The initial vertical folds are the first to form on the body of the fetus.
Their presence seems to be due to the cellular division process of the embryo.
The zygote divides in two, then four, eight, ... and these separations leave some traces on the body of the fetus.
The initial folds are all vertical
Initial folds divide the body into halves, quarters and eighths along the vertical axis.
The most important is the vertical center fold.
© Carnegie Collection Embryo No.6473
© Carnegie Collection Embryo No.8098
You can observe the central vertical division. It will later lead to the formation of the vertical center fold.
Since initial vertical folds are the first to appear, they are refolded when new ones cross them.
Usage folds - Temporary and permanent
Usage folds are created by all your movements, positions and expressions.
They can be grouped into the following categories:
Many of these folds start developing in the fetal stage, but only after the initial vertical folds have formed.
The horizontal folds on this baby's fingers started forming several weeks before birth.
A six-week-old human embryo can arch its back and neck. By seven weeks, movement in the arms and legs can be detected by ultrasound.
Permanent folds and body movements
Flex your wrist several times and take a close look at the folding that this action creates.
Permanent folds on the wrist
Notice that some folds do not disappear completely when the articulation is straight.
These folds seem etched into your body because you have done this movement so frequently throughout your life.
Those are permanent folds.
Permanent fold formation
When the folding in the skin occurs at the same place repeatedly, your system generates epidermis cells to pave the bottom of the fold's groove.
Coats of fresh epidermis cells hold the fold in place and prevent any damage to the skin.
A wrinkle is simply the first step in the formation of a permanent fold.
With time, a wrinkle will become a fold.
Every large fold on your body has started out as a wrinkle.
When permanent folds first establish themselves, they pave the bottom of the crease, layer by layer, with epidermis cells.
It may take several years before the fold to becomes plainly visible.
The coats of epidermis cells that hold the fold in place are produced slowly over time.
We all have similar folds
Similar folds on everyone
When I first found out about the folds, I thought that each human was folded differently, explaining the diversity of our looks.
Well, I was half wrong.
In fact, most folds are common and comparable from one human to another.
We look different because some folds have a slightly different position and depth, but mostly because of our bone structure beneath.
The similarities are much greater than the differences.
We are all folded the same way.
Differences often lie in the size, angle and depth the same fold can take among humans.
Early in life, the shape of the skull is very important, the alignment of its parts particularly.
For example, the fold going from the side of the eye to the top of the ears is obviously affected by their respective positions.
Most of the distinctions come from how big the fold has become along its path.
This, in turn, depends on each individual's actions.
The way your nose is twisted, the way your eyes look, the way your eyebrows are formed, ... represent years of nose twitching, eye squinting or worried facial expressions.
Folds are illustrated here as simple lines.
They are not so on your body.
Each fold is a complex monster with thousands of details.
They are made of several coats, each one with a real life history.
A typical fold has hundreds of coats.
They are also far from straight.
Folds multiply, so you may find several parallel folds instead of one when you check on your body.
Why are the folds so hard to see?
Three main reasons explain why your sight is deceived;
1• The skin's wound healing process paves over them
Your skin considers folds and their crossings as injuries and tries to repair the damage.
The wound healing process coats every hole and crack with fresh epidermis cells to preserve the skin's integrity.
2• All you see are the seams
Folds and their crossings keep on growing and become huge intra-cutaneous structures.
They do this by deepening and bringing more and more skin into them.
Their entire mass is beneath the surface and from the outside, all you can see is a simple seam.
Seam on a coat
3• It's all epidermis
Most of the folding is hard to distinguish, because it is made of epidermis over epidermis.
A very tight seam, with no stitches, with perfect color matching is not easy to detect.
Even a microscope would only reveal patterns of epidermis cells.
To your ultra-sensitive nails and fingertips though, the folds are like mountains and canyons.