S Foote.
Experienced Member
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Trying to be layperson friendly about science.
There are a lot of debates on hair loss forums, that involve what seems to be very complicated scientific issues and processes. Often people ask if these arguments can be described in a way lay people can better understand, and this is my attempt to explain my proposal in such terms.
On the surface science can seem very complicated. This is why the scientific method is taught as a way to work through the apparent complication. The scientific method is just basic common sense, and trying to keep things as simple as possible. Its really all about trying to find the simplest possible explanation. Any explanation that has to add unnecessary complication, is likely to be wrong according to the scientific method.
Keeping the descriptions here as simple as possible.
There is no disagreement on the central question about changes in hair growth. Every hair cycle a new follicle grows in the dermal tissue. The period of this growth phase and the size the follicle grows to, determines how much hair the follicle produces. A long growth phase means a larger follicle and more hair growth, a short growth phase means a smaller follicle and less hair growth. In most cases of hair loss the follicles become very small cycle by cycle.
So the basic question is what causes follicles to change their size in this way?
Most of the discussion about this, looks for changes at the molecular level that may explain the growth changes in follicles. From this point of view it seems very complicated, with lots of various interactions going on. But from another point of view, this process of change becomes very simple to understand.
You don't always need to know how something works at the molecular level, to know how it works at the functional level. I will make a simple analogy.
You don't need to know about the molecular basis of how your car works or all the interactions involved, to know that a certain control performs a certain function. Its what happens at the functional level that matters. It is the same in biology.
There is already a recognised tissue growth control in biology, that operates at the functional level.
This very simply explains the recognised growth changes in hair follicles. To understand how this is relevant here, you have to consider what we know about hair follicles in terms of evolution and their original purpose.
Hair or fur originally evolved as an insulator in mammals, and is an important part of the mammals temperature control system. To be effective hair has to be temperature responsive, increasing in cold conditions and reducing in warmer conditions. There has also got to be a way to shed hair when it matters, particularly around injuries. This is because hair close to injuries can hold dirt etc, and promote infection. Hair loss here allows the animal to clean the wound. So hair growth needs to be adjustable according to conditions.
How the hair cycle "builds" the follicle, and the finished structure is important here.
The first diagram here shows the changing size of follicles during the hair cycle. The second diagram shows the finished hair producing follicle, in the dermal system. The end product here is a pocket with the hair production area at its base, these are the significant features.
Dia 1
Dia2
The enlargement of the follicle within the dermal system, means the dermal tissue around it has to move out of the way. So the resistance, best thought of as "springiness" of the surrounding tissue is important. We know that tissue growth can be stopped by external pressure, and reducing that pressure allows tissue growth to continue.
http://www.pnas.org/content/111/15/5586.abstract
This normal external growth control, is all that is needed to explain the changes in hair follicle size. It is not necessary to know about all the molecular details involved!
The hair follicle wants to enlarge during the anagen period, what restricts this is the springiness of the tissue around it. The harder the spring, the earlier the switch off point is reached. This means a small follicle and reduced hair growth. The softer the spring, the more the follicle can enlarge before the switch off point is reached. You get a larger follicle and more hair growth. So it is the natural springiness of the dermal tissue around the follicle that determines follicle size and hair growth.
If all this is true, any changes in follicle size will be because of changes in the springiness of the surrounding tissue. We should also remember that even large follicles are small structures, so even small scale changes make a difference.
The primary response to cold in mammals, is to shift the dermal blood flow lower in the dermis to conserve heat. The reverse happens in a hot climate, and blood flow increases in the surface tissue to help get rid of body heat.
These changes in dermal blood supply change the tissue fluid pressures, and the springiness of the tissue around the follicles.
In hot conditions the increased fluid pressure around follicles, increases the springiness making it harder for follicles to enlarge and hair growth reduces. The reverse applies in cold conditions and the follicle can enlarge more. There is another effect based upon the pocket structure of follicles.
The hot response of increasing surface tissue fluid pressure, expands this tissue. This moves the surface of the skin and the attached pocket element of the follicle, away from the hair production area set in the lower tissue. You can see from diagram 2 that such movement would reduce the production area from the outside inwards. This reduces hair growth from follicles already in full anagen. In longer follicles this effect is magnified, and the production area reduces to zero. The hair detaches with the noted club hair shape, reflecting the reduced growth from the outside in to the centre.
The overall effect in response to heat, is a moult and reduced hair growth. With the opposite effect in cold conditions of increased hair growth and volume, ie the winter coat. This is the most simple way possible to adjust hair growth in mammals, in hairs original function as an insulator.
Where you have a significant increase in tissue expansion such as swelling induced by an injury, all the local follicles will be distorted as described and the hair will be shed. Allowing cleaning and reduced risk of infection.
This simple interaction between the hair cycle, follicle structure, and pressure changes in the surrounding tissue, offers all that is required from mammalian hair growth in terms of evolution.
In modern humans, anything that changes these factors, will also change hair growth. The principles of this hair growth mechanism have wider implications than just hair growth. In my opinion this tells a story of human evolution, general physiology, and some gender related diseases. There is also testing that can be done here.
The principle is that hair growth is set by the springiness of the surrounding tissue, modified by changes in local tissue fluid pressure.
Most of the changes in human hair growth have a link with changes in tissue fluid pressure. Inflammatory processes increase tissue fluid pressures. Local edema or tissue swelling is a known effect of many hormone imbalances. In radiation sickness and chemotherapy, the cell damage causes rapid edema. Many treatments that improve hair growth are also known to reduce tissue fluid pressures.
We know that humans also lose hair around injuries, commonly called shock loss.
We can also get some insight here, on the changes necessary to produce modern human hair patterns. There is a clear example of this hair growth mechanism in humans, that anyone can check out for themselves.
Why is it that we get the isolated strips of increased hair growth, we call eyebrows?
If you raise your eyebrows and run your finger down from above them, you can feel the difference in the tissue they grow from. This tissue is softer than the surrounding tissue, you can feel the boundary. This allows increased follicle enlargement and the increased local hair growth.
In my opinion eyebrow growth perhaps reflects our original "fur", and understanding what makes the surrounding tissue different could be important in understanding human evolution.
I think this is as simple and as understandable, as i can make this proposal.
There are a lot of debates on hair loss forums, that involve what seems to be very complicated scientific issues and processes. Often people ask if these arguments can be described in a way lay people can better understand, and this is my attempt to explain my proposal in such terms.
On the surface science can seem very complicated. This is why the scientific method is taught as a way to work through the apparent complication. The scientific method is just basic common sense, and trying to keep things as simple as possible. Its really all about trying to find the simplest possible explanation. Any explanation that has to add unnecessary complication, is likely to be wrong according to the scientific method.
Keeping the descriptions here as simple as possible.
There is no disagreement on the central question about changes in hair growth. Every hair cycle a new follicle grows in the dermal tissue. The period of this growth phase and the size the follicle grows to, determines how much hair the follicle produces. A long growth phase means a larger follicle and more hair growth, a short growth phase means a smaller follicle and less hair growth. In most cases of hair loss the follicles become very small cycle by cycle.
So the basic question is what causes follicles to change their size in this way?
Most of the discussion about this, looks for changes at the molecular level that may explain the growth changes in follicles. From this point of view it seems very complicated, with lots of various interactions going on. But from another point of view, this process of change becomes very simple to understand.
You don't always need to know how something works at the molecular level, to know how it works at the functional level. I will make a simple analogy.
You don't need to know about the molecular basis of how your car works or all the interactions involved, to know that a certain control performs a certain function. Its what happens at the functional level that matters. It is the same in biology.
There is already a recognised tissue growth control in biology, that operates at the functional level.
This very simply explains the recognised growth changes in hair follicles. To understand how this is relevant here, you have to consider what we know about hair follicles in terms of evolution and their original purpose.
Hair or fur originally evolved as an insulator in mammals, and is an important part of the mammals temperature control system. To be effective hair has to be temperature responsive, increasing in cold conditions and reducing in warmer conditions. There has also got to be a way to shed hair when it matters, particularly around injuries. This is because hair close to injuries can hold dirt etc, and promote infection. Hair loss here allows the animal to clean the wound. So hair growth needs to be adjustable according to conditions.
How the hair cycle "builds" the follicle, and the finished structure is important here.
The first diagram here shows the changing size of follicles during the hair cycle. The second diagram shows the finished hair producing follicle, in the dermal system. The end product here is a pocket with the hair production area at its base, these are the significant features.
Dia 1
Dia2
The enlargement of the follicle within the dermal system, means the dermal tissue around it has to move out of the way. So the resistance, best thought of as "springiness" of the surrounding tissue is important. We know that tissue growth can be stopped by external pressure, and reducing that pressure allows tissue growth to continue.
http://www.pnas.org/content/111/15/5586.abstract
This normal external growth control, is all that is needed to explain the changes in hair follicle size. It is not necessary to know about all the molecular details involved!
The hair follicle wants to enlarge during the anagen period, what restricts this is the springiness of the tissue around it. The harder the spring, the earlier the switch off point is reached. This means a small follicle and reduced hair growth. The softer the spring, the more the follicle can enlarge before the switch off point is reached. You get a larger follicle and more hair growth. So it is the natural springiness of the dermal tissue around the follicle that determines follicle size and hair growth.
If all this is true, any changes in follicle size will be because of changes in the springiness of the surrounding tissue. We should also remember that even large follicles are small structures, so even small scale changes make a difference.
The primary response to cold in mammals, is to shift the dermal blood flow lower in the dermis to conserve heat. The reverse happens in a hot climate, and blood flow increases in the surface tissue to help get rid of body heat.
These changes in dermal blood supply change the tissue fluid pressures, and the springiness of the tissue around the follicles.
In hot conditions the increased fluid pressure around follicles, increases the springiness making it harder for follicles to enlarge and hair growth reduces. The reverse applies in cold conditions and the follicle can enlarge more. There is another effect based upon the pocket structure of follicles.
The hot response of increasing surface tissue fluid pressure, expands this tissue. This moves the surface of the skin and the attached pocket element of the follicle, away from the hair production area set in the lower tissue. You can see from diagram 2 that such movement would reduce the production area from the outside inwards. This reduces hair growth from follicles already in full anagen. In longer follicles this effect is magnified, and the production area reduces to zero. The hair detaches with the noted club hair shape, reflecting the reduced growth from the outside in to the centre.
The overall effect in response to heat, is a moult and reduced hair growth. With the opposite effect in cold conditions of increased hair growth and volume, ie the winter coat. This is the most simple way possible to adjust hair growth in mammals, in hairs original function as an insulator.
Where you have a significant increase in tissue expansion such as swelling induced by an injury, all the local follicles will be distorted as described and the hair will be shed. Allowing cleaning and reduced risk of infection.
This simple interaction between the hair cycle, follicle structure, and pressure changes in the surrounding tissue, offers all that is required from mammalian hair growth in terms of evolution.
In modern humans, anything that changes these factors, will also change hair growth. The principles of this hair growth mechanism have wider implications than just hair growth. In my opinion this tells a story of human evolution, general physiology, and some gender related diseases. There is also testing that can be done here.
The principle is that hair growth is set by the springiness of the surrounding tissue, modified by changes in local tissue fluid pressure.
Most of the changes in human hair growth have a link with changes in tissue fluid pressure. Inflammatory processes increase tissue fluid pressures. Local edema or tissue swelling is a known effect of many hormone imbalances. In radiation sickness and chemotherapy, the cell damage causes rapid edema. Many treatments that improve hair growth are also known to reduce tissue fluid pressures.
We know that humans also lose hair around injuries, commonly called shock loss.
We can also get some insight here, on the changes necessary to produce modern human hair patterns. There is a clear example of this hair growth mechanism in humans, that anyone can check out for themselves.
Why is it that we get the isolated strips of increased hair growth, we call eyebrows?
If you raise your eyebrows and run your finger down from above them, you can feel the difference in the tissue they grow from. This tissue is softer than the surrounding tissue, you can feel the boundary. This allows increased follicle enlargement and the increased local hair growth.
In my opinion eyebrow growth perhaps reflects our original "fur", and understanding what makes the surrounding tissue different could be important in understanding human evolution.
I think this is as simple and as understandable, as i can make this proposal.
