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  #1  
Old 09-22-2013
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Microscope Hypertrophy versus Hyperplasia

Hey!

So this might be simple stupid question!

It's mention in Pathoma that with permanent cells such as Cardiac, Skeletal, Neurons only hypertrophy occurs not hyperplasia such as Hypertrophy in left ventricle in CHF.

What about skeletal muscle in children when they are growing? Wouldn't that be technically hyperplasia at that moment? Or is skeletal tissue only "permanent" in adults?



Thanks!
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  #2  
Old 09-22-2013
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*big facepalm*

please re-re-re-re-re-re-read the definition of hyperplasia first then ask again... then you will see that what you asked sounds stupid


[ we all have been through the overthinking phase]
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Old 09-22-2013
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Yes I know it says;

Hyperplasia involves the production of new cells from stem cells.

Hypertrophy: Involves gene activation, protein synthesis, and production of organelles.

Permanent Tissues: Cardiac Muscle, Skeletal Muscle, and Nerve and they only go hypertrophy only.

My question is as adults our muscles are much bigger than kids. So from going from a kid to an adult would that be hypertrophy according to the definition or hyperplasia? We can't grow new cells from the cells that are permanent.

Also such as an infant's heart is so small and when they become an adult what is that going through?

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Old 09-22-2013
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It IS a thoughtful question. It's a healthy habit, thinking beyond the given information. Let me try to explain.
Technically, muscle building (in adults and someone like Sylvester Stallone) would be hypertrophy. What's happening is "new sarcomeres" are being added within the already existing myocytes. So the increase in muscle bulk is due to increased bulk of individual muscle fibres, not increase in number of myocytes as one might think.
Similarly with cardiac hypertrophy (pathological)
Volume overload ---> new sarcomeres laid in series ---> eccentric hypertrophy
Pressure overload ---> new sarcomeres laid parallel to existing ones ---> concentric hypertrophy

You may also find cells known as "satellite cells" in some histology texts which are supposed to be "skeletal muscle stem cells". But from what I've read, their function is again to add more myofibrils to the existing myocytes in an attempt to repair them after a vigorous exercise.
Don't get confused. Bottomline is - skeletal muscle, cardiac muscle amd neurons ARE in fact permanent cells.

Cheers.
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Old 09-23-2013
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I am sorry but I am a bit confused still.

So going from an infant to an adult is through an increased number of sarcomeres?

Thanks for helping me out!
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Old 09-23-2013
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Yeah about that, I guess so. I haven't actually read something like that specifically in a text but I HAVE read the thing about "building" muscles in athletes. So I deduce by common principal that it has to be the same case in infants vs adults as well.
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Old 09-23-2013
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Haha thanks boss! Appreciate it!
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Old 09-23-2013
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No worries

Just to give you more perspective - HOCM is a disease involving mutations of sarcomere proteins causing cardiac muscle "hypertrophy" (not hyperplasia). Just google a few images of HOCM and observe how gigantic that IV septum becomes (almost 3-4 times!). Can't be hard to imagine the same occurring physiologically in a more slow and subtle way in normal human growth.
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