jackson6612 said:
Yes, you are right that hair follicles can be regarded as organs. But, isn't this also true for many other things? Like, it can argued any tissue could consist of many sub-tissues where each group of cells (a sub-tissue) is doing a particular job. I think that depends how far or deep you seek to go and how you want to categorize things.
Hello Jack
You are quite correct about the lack of any absolute distinction between tissues and organs. This is not a matter of the right or the wrong term, but the right or the wrong context. Certainly one cannot look at an eye and claim that it is not an organ but a tissue, and the same applies to a hair follicle. But then, think of the papilla in the hair follicle. It looks much like a tiny lump of undifferentiated tissue, but in fact parts of it are responsible for producing the central part of the hair shaft, the medulla, and different parts produce the outside, the cortex.
As you can see, it is not just a matter of categorising things much as a stamp collector might save a stamp on one page or another, but the use of a term that reflects the function and structure of a part of a living creature. Do not think that the example of that hair papilla is extreme. Consider the feather papilla of a bird; its function is vastly more complex than a hair papilla, and yet it also looks like no more than a little lump of tissue.
This is a concept that often arises. Think of the fat of a mammal. It is obviously tissue, isn't it? Yes, making allowance for the fact that fat in different parts of the body is not all the same, it is tissue. And yet nowadays we know that fat tissue has many functions beyond storing fats. It is common to speak of the adipose organ in the proper context.
Does that mean that we should not speak of fat tissue? Not at all, but it does mean that it makes sense for us to choose the word we use to suit the sense that we wish to make.
On several occasions I have been accused that many times I ask questions answers for which can be obtained from the internet. (I'm not saying you are also doing the same, you are simply instructing me). Yes, it is true the net is essentially a depository of knowledge. We all learn in different ways and that too under different circumstances. I find the net entries distracting where there are so many concepts crammed within a single article and I go in searching for answers to just a few questions and come out totally confused with so many new confusions. Wikipedia is an excellent resource and I use it a lot. But you would agree many of the times articles, especially scientific ones, are difficult for a layman to understand. As I can see you are good at your subject and the articles related to your subject might appear very simple and straightforward to you. You have simply advanced to a higher position in the hierarchy of knowledge and I'm simply a layman and there is no denying or shame about it. Those articles are difficult for me. The advantage of asking questions to people here in live discussions is that I can keep track of the points without sacrificing the coherence of thought and without being engulfed by many new baffling points.
Never mind people who direct you to the Internet for every bit of advice you need. Certainly most of what you would need is there to be found, but it does not follow that the layman, or even the non-native English speaker, will know what to look for or how to look for it. What is worse, it can be very difficult to know what to trust. However, when we direct you to Google or Wikipedia, or an url we usually have a particular reason. If you find the material we direct you to is too difficult, then by all means come back and ask us to explain. I don't think you will find many of us will object. Of course there is the occasional rude person, but one of the nice things about a blog site like this one is that they are in the minority and easy to ignore.
The current topic reminds me of another question which I wanted to ask earlier. I have observed that after hairs, scalp hair or body hair, have grown to a certain length, their rate of growth becomes very slow. In other words, if it took one month to grow them to two inches, then it would take quadruple time to add further two inches to the length. Why is so?
There are two factors here. Firstly, subjectively, when a hair is about 1mm long and grows another mm in a day, it has doubled its length and seems to grow fast. Ten days later, it is about 1cm long and still only grows to 11mm the next day, a 10% increase: slow!
There can also be an objective effect. If it grows 50mm in a month and another four months to grow the next 50mm, then the problem is slower growth. This is a result of the hair growth cycle. Consider
air on different parts of the body grows differently. An eyelash begins by growing thin, then thicker, then thinner again, then it stops growing. After a few months it falls out and the whole thing starts over.
The hair on your head generally has a much longer and simpler cycle, a scalp hair might grow for many months or a few years before falling out. During most of that period it will grow, but generally faster at the beginning of the cycle than near the end.
Other hairs on your body have their own cycles, and on many other species of mammals there are far more, and more complex, cycles than I am sure you ever have imagined. They affect colour, texture, insulation, water repellency and a whole range of qualities. Compare the coat of a cat with that of a horse, an otter or an elephant.
Hair is a dead structure. People say a hair is a dead cell. Is this correct to call it a cell? I think it's a misnomer. A single hair strand, shaft could be regarded as made up of threads of proteins (I don't know if it's a single protein or many) twisted together. In biology a cell is a different thing.
Anyone who tells you that a hair is a dead cell is wrong. You are quite right about it being a misnomer, and in fact it is a total misunderstanding. Any part of the hair that has left the follicle certainly is dead, but it is not one dead cell, but thousands or millions. And those cells are not all the same. They differ even in the same hair, and tremendously in different species. Compare the hair of for example, a chinchilla with a porcupine. For that you do not need a microscope, though it might help.
Not just any dead cell makes hair. The cell has to be properly prepared and properly matured. The hair shaft contains hundreds or thousands of kinds of proteins; after all, it is made of cells that once were alive and cells contain many proteins. However, there are special proteins in hairs, each with a special function, but the best-known hair protein is called keratin. It starts out within the living cells as separate packets, but as the cells die and mature they lose a lot of their structure and the keratin unites into a combined structure.