Folded skin theory, evolution and pathology
Folds are very problematic for your skin.
A fold starts out as a groove in your skin, an inward indentation with very little consequences.
Their number and depth increases all your life.
However, when repeated folding causes the fold to become permanent, it has repercussions on many components of the skin and on everything that lies beneath it.
Skin is a living tissue
Skin is a multi-layered tissue containing a large number of living constituents that are essential to your well-being such as: sweat glands, hair follicles, sebum glands, specialized receptors for pain, touch, temperature, vibration, ....
Every section of your skin is irrigated and innervated by a complex system of branching blood vessels and free nerve endings.
The layers of a non-folded skin
Skin is flexible and extensible, it folds easily.
This suppleness is essential, because the skin covers articulated parts of the body where it gets stretched, compressed and creased.
It has to fold.
Folds deteriorate the skin
Even if the folds are a normal occurrence, they degrade the skin.
Occasional folds become permanent ones.
Strips of skin stay imprisoned inside the folds and this situation cannot be considered as healthy.
Both sides of the fold become walls, facing each other.
They are held together by a filling composed mostly of hardened epidermis cells and sebum.
Types of folds
Several attributes can be used to distinguish and differentiate the folds in human skin.
Folds can be grouped according to their orientation, their depth and their angle, but mostly by their location, their progression, ...
Occasional and permanent folds
Folds have two phases in their evolution;
•At first, they are not etched into the skin and only appear when a movement creates them.
•Then, they slowly solidify, deepen, harden and tighten to become permanent.
The folds start out as occasional events, but at some point, they build up and consolidate to become permanent.
At birth, humans already exhibit several permanent folds that were formed because the actions of the fetus during pregnancy.
The evolution of the fold and the processes involved are described lower on this page.
-How long is a fold?
-Most folds are circular.
Folds have a tendency to go for as long as they can.
For this reason, most large ones circle completely around your body.
The folds keep on going until they fall back in their own crease.
Usually, some sections of each fold are visible, but long stretches can be completely undetectable, even when looking closely.
Fortunately, the folds can be felt with your super sensitive fingertips and nails.
Circular folds with invisible sections
The circular folds on fingers are plainly visible on the top and bottom, but invisible on the sides.
The vast majority of the folds on your body go all the way around it, even vertically up and down.
Some folds that are specific to a particular feature, such as the mouth, may circle around it.
Most diagonal folds aren't circular; they have short paths and are placed between two large fold crossings.
Most folds are caused by movements of the body.
The body is segmented and can only bend in specific places; at the articulations.
The skin that covers them is tubular.
Fingers, arms, legs, neck, trunk, ... all these tubes are vertical.
The joints only work in one way and do not permit flexing in the opposite direction.
This means that the skin tubes are always bending on the same side.
The folds occur mostly at articulations.
Articulations are really problematic.
The skin covering these moving parts gets repeatedly stretched, compressed and crumpled.
Anytime you flex a joint, several folds are formed.
The skin becomes pleated and some sections are pressed into the articulation.
When the skin gets attached and entangled into the mechanism, pain can be generated anytime the articulation is flexed.
Compressed and stretched folds
The structure of each articulation only permits flexing in a specific manner.
The extent and direction of their motion is limited.
Joints can bend easily on one side, but not on the other.
Because of this, a different kind of folds will develop on each side of an articulation.
Articulations only bend on one side,
producing two kinds of folds.
•Compressed folds; On the inside of the articulation; where the skin is squeezed and constricted. They tend to be few in number, but tightly folded and deep.
•Stretched folds; On the outside of the articulation; where the skin is spread and expanded when the joint is closed, but it drapes and dangles when it is straightened. They are small and numerous, but they ain't as deep.
You will find stretched and compressed folds at every articulation on your body
Both types meet on the sides of the skin tubes, creating circular horizontal folds.
Complete folds and surface folds
Folds can also be differentiated by their depth, so you will find:
Complete folds; where the whole skin, epidermis, dermis and hypodermis, is entirely bent over.
Many complete folds are formed early in the life of an individual, when the skin is still supple and thin, but they keep on developing until you die.
Complete folds start out as surface folds.
Surface folds; also called wrinkles, where shallow and small grooves only bend the top of the skin.
They proliferate by creating lines between your existing fold crossings.
Most folds aren't perpendicular to the skin’s surface.
Their path is angled because one side receives more pressure.
In some cases, the walls of the fold become almost parallel to the skin’s surface.
Your body considers folds as wounds.
Skin responds to excessive folding
Your skin can endure a lot of folding without damage.
But, when the folding occurs in the same places, over and over, day after day, because of your repetitive movements; your skin can't take it.
Damage done by repeated folding
If your skin was to be folded only occasionally, of course no damage would occur.
But think of how often you wink, swallow, talk or eat and you’ll understand that folding represents a real challenge for your skin.
You know the impact folding has on objects.
You probably fold some things repeatedly to separate or divide them.
Fold repeatedly to break apart
How damaging the process is depends on;
•The rigidity and elasticity of the folded material,
•How long you do it,
•At what speed,
•What vigor is applied,
Repeated folding provokes specific epidermis formation
When the skin is folded repeatedly, heat builds-up on the floor of the fold.
The structural integrity of the material is put to test and some is mutilated in the process.
Luckily, skin is unbelievably flexible and elastic.
It can be folded thousands of times without damage.
Repeated folding generates heat.
However, when things get real hot, your skin has to protect itself.
Your skin treats folds as injuries and tries to repair their damage.
The heat build-up triggers specific epidermis formation into action.
This wound healing process involves the formation of layers of epidermis cells at the bottom of the fold to protect the skin.
Coating the fold’s floor with epidermis cells
While the repeated folding is occurring, the excess heat is concentrated all along the path of the fold, on its floor.
In reaction, the skin will pave the bottom of the fold’s route with a fresh coat of epidermis to prevent any tearing.
A new coat of epidermis inside a fold
Over time, epidermis formation will come into action several times on the same fold.
Epidermis cells hold the fold in place and prevent any tearing.
The fold has become permanent.
If a fold meets an obstacle on its path, such as a bone beneath the skin or simply another fold, a hot spot is created.
The epidermis formed at the point where the fold and the obstacle meet will slowly link and attach them together.
This phenomenon greatly reduces the skin’s mobility causing an anchoring effect.
Folds growing inwards coat by coat
Each time epidermis formation paves the fold, it strengthens and hardens it.
Each new coat finds a new, evolved situation.
Conditions have changed slightly.
Each point in the fold experiences changing pressures, and these affect the shape of its growth.
This results in a different epidermis structure for each new coat.
As the number of coats increases, unfolded skin at the top is pulled down, and the whole edifice deepens into the flesh.
Epidermis coats inside a fold
Coats and grooming
When you groom a fold, it unfolds coat by coat.
You can feel each coat yielding beneath your nail.
The consequences of folded skin
Inoperative trapped skin components
Part of the skin becomes engulfed into the fold.
Some hair follicles and sweat glands, that normally expulse their content at the surface, now see their exits blocked.
Most of their vital functions, hair, sebum and sweat production, are halted.
It is like if time was suspended for them.
Hair stops growing and doesn't even whiten.
Cellulite is characterized by visible patterns of bumps and lines on the skin.
Of course, those lines are caused by deep folds.
Cellulite can be groomed away with pressure strokes.
• Stretch marks
Stretch marks, also called «Striae», are simply folds that are pulled open by an enlargement of part of the body usually due to puberty, pregnancy, muscle building, weight gain, ...
Normally, the folds are kept closed by the epidermis formed within each one to protect the skin against tearing.
When a sudden growth happens, the stretching pulls on the skin and opens some folds.
Since part of their protective hardness is removed, they feel soft.
Stretch marks follow parallel fold patterns
Stretch marks can often be observed as parallel grooves in the skin.
This parallelism and their generally vertical orientation only validate the fact that they are folds.
• Varicose veins - Blood flow obstructed by folds
Folds hamper blood circulation.
When blood vessels get near a fold, they get flattened and crushed.
Their passages become constricted so the blood can't flow normally.
The veins enlarge because the blood can't go forward anymore.
Their visibility augments.
The blood vessels have to swerve around the folds to continue their course.