<p>As <a href="https://en.m.wikipedia.org/wiki/Myelin" rel="nofollow noreferrer">Wikipedia points out</a>:</p>

<blockquote>
  <p><strong>Myelin</strong> is a lipid-rich (fatty) substance formed in the central nervous system (CNS) by glial cells called <a href="https://en.m.wikipedia.org/wiki/Oligodendrocyte" rel="nofollow noreferrer">oligodendrocytes</a>, and in the peripheral nervous system (PNS) by <a href="https://en.m.wikipedia.org/wiki/Schwann_cell" rel="nofollow noreferrer">Schwann cells</a>.</p>
</blockquote>

<p>When referring to the sheath, you are referring to the covering which is made of myelin.</p>

<blockquote>
  <p>Myelin sheaths are sleeves of fatty tissue that protect your nerve cells from damage (<a href="https://www.webmd.com/multiple-sclerosis/myelin-sheath-facts" rel="nofollow noreferrer">WebMD</a>).</p>
</blockquote>

<p>The thing is that myelin formed in the CNS and PNS is only used in the form of a sheath  to protect your nerve cells, so when physicians refer to the myelin, they are referring to the sheath.</p>

<p>With demyelination, the integrity of the sheath is being compromised.</p>

CC BY-SA 4.0
2019-08-19T00:07:52.377Z
So it seems I was right. But my question was not what Myelin is as opposed to the Sheath. But rather asking for an explanation of the weird fact that Physicians and Media use Myelin to mean the specific structure. Demyelination is not weird because if something loses it's myelin it could not possibly keep its myelin sheath made out of that same myelin that was supposed to be Lost.
George Ntoulos
CC BY-SA 4.0
2019-08-19T00:12:20.390Z
Might be worth adding that myelin is really only found in sheaths...so, referring to myelin is basically the same thing as referring to the sheath.
Bryan Krause
CC BY-SA 4.0
2019-08-19T08:40:54.637Z
@BryanKrause - I agree and added that in for clarity.
Chris Rogers
CC BY-SA 4.0
2019-08-19T19:21:18.520Z
@ChrisRogers This does not change the fact that textbooks make a clear distinction. Myelin can be extracted from the sheath and it will still be myelin. It will not be the Sheath.
George Ntoulos
CC BY-SA 4.0
2019-08-19T19:23:26.893Z
But it will not be naturally used by the body other than for the original purpose @GeorgeNtoulos
Chris Rogers
CC BY-SA 4.0
2019-08-19T19:34:50.730Z
@ChrisRogers Aples and Oranges. One thing has nothing to do with the other. Myelin not being naturally used by the body for any other reason does not make the term for the Sheath. Myelin. Myelin is the substance itself regardless of structure while Myelin Sheath is the anatomical structure.
George Ntoulos
CC BY-SA 4.0
2019-08-19T20:40:51.890Z
@GeorgeNtoulos Can you point to a single example where someone refers to "myelin" where they are not referring to the sheath? Myelin is not a special substance, it's phospholipid membrane. If it wasn't in a sheath you wouldn't call it myelin. One could argue that calling it a "myelin sheath" is redundant, but sometimes redundancy is accepted in language.
Bryan Krause
CC BY-SA 4.0
2019-08-18T06:35:47.627Z
2019-08-19T08:40:18.430Z
2019-08-19T08:40:18.430Z
Chris Rogers
<p><a href="https://medlineplus.gov/ency/article/002261.htm" rel="nofollow noreferrer">https://medlineplus.gov/ency/article/002261.htm</a></p>

<p>Why is Myelin used as a term to mean the Myelin Sheath as opposed to the proper term?</p>

<p>It is apparent to me that Myelin is the substance itself regardless of structure and the Myelin Sheath is the structure around the axis to insulate Electro-Chemically the nervous system composed of this substance.</p>

<p>But Media and Physicians frequently use Myelin instead of Myelin Sheath as opposed to textbooks that make the distinction</p>

<neuroscience><terminology><neural-network><neurophysiology><neuroanatomy>
Myelin and Myelin Sheath
George Ntoulos
# Myelin and Myelin Sheath

(Asked by: username_0 on 2019-08-18)

<https://medlineplus.gov/ency/article/002261.htm>

Why is Myelin used as a term to mean the Myelin Sheath as opposed to the proper term?

It is apparent to me that Myelin is the substance itself regardless of structure and the Myelin Sheath is the structure around the axis to insulate Electro-Chemically the nervous system composed of this substance.

But Media and Physicians frequently use Myelin instead of Myelin Sheath as opposed to textbooks that make the distinction

**Tags:** neuroscience, terminology, neural-network, neurophysiology, neuroanatomy


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## 1 answers

### Answer by username_1 on 2019-08-18. Score: 4

As [Wikipedia points out](https://en.m.wikipedia.org/wiki/Myelin):

> **Myelin** is a lipid-rich (fatty) substance formed in the central nervous system (CNS) by glial cells called [oligodendrocytes](https://en.m.wikipedia.org/wiki/Oligodendrocyte), and in the peripheral nervous system (PNS) by [Schwann cells](https://en.m.wikipedia.org/wiki/Schwann_cell).

When referring to the sheath, you are referring to the covering which is made of myelin.

> Myelin sheaths are sleeves of fatty tissue that protect your nerve cells from damage ([WebMD](https://www.webmd.com/multiple-sclerosis/myelin-sheath-facts)).

The thing is that myelin formed in the CNS and PNS is only used in the form of a sheath to protect your nerve cells, so when physicians refer to the myelin, they are referring to the sheath.

With demyelination, the integrity of the sheath is being compromised.

> **Comments:**
> **username_0**: So it seems I was right. But my question was not what Myelin is as opposed to the Sheath. But rather asking for an explanation of the weird fact that Physicians and Media use Myelin to mean the specific structure. Demyelination is not weird because if something loses it's myelin it could not possibly keep its myelin sheath made out of that same myelin that was supposed to be Lost.  
> **username_2**: Might be worth adding that myelin is really only found in sheaths...so, referring to myelin is basically the same thing as referring to the sheath.  
> **username_1**: @BryanKrause - I agree and added that in for clarity.  
> **username_0**: @ChrisRogers This does not change the fact that textbooks make a clear distinction. Myelin can be extracted from the sheath and it will still be myelin. It will not be the Sheath.  
> **username_1**: But it will not be naturally used by the body other than for the original purpose @GeorgeNtoulos  
> **username_0**: @ChrisRogers Aples and Oranges. One thing has nothing to do with the other. Myelin not being naturally used by the body for any other reason does not make the term for the Sheath. Myelin. Myelin is the substance itself regardless of structure while Myelin Sheath is the anatomical structure.  
> **username_2**: @GeorgeNtoulos Can you point to a single example where someone refers to "myelin" where they are not referring to the sheath? Myelin is not a special substance, it's phospholipid membrane. If it wasn't in a sheath you wouldn't call it myelin. One could argue that calling it a "myelin sheath" is redundant, but sometimes redundancy is accepted in language.  

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