00:00
Let's talk about hypertrophy,
kind of the flipside of the coin.
00:04
Hypertrophy is an
increase in cell size.
00:07
So this gentleman shown here has exactly
the same amount of skeletal muscle.
00:13
Cells as I do, and yet his arm
looks a whole lot better than mine.
00:17
You can't see it through the
jacket, but this is better.
00:20
He doesn't have
any more muscles.
00:22
He just has bigger cells.
00:25
So, as a result of the
increased size of cells,
the organ apparently
gets bigger too.
00:30
So it happens with not only just
muscle but with other tissues.
00:35
We want to distinguish this
process from hyperplasia.
00:38
Hyperplasia means more cells number not
more cell size, but more cell number.
00:43
So we will come to
hyperplasia next.
00:45
It's reversible.
00:47
So, Arnold Schwarzenegger
used to look like that.
00:49
If you see Arnold Schwarzenegger
now, his muscles are more like mine,
and that's because he's not
working out at quite the same rate.
00:57
He doesn't have the
same hypertrophy.
00:59
So it's reversible, for
example, in skeletal muscle.
01:01
It's also reversible
in cardiac muscle.
01:04
So this is just an example
of the top figure shows.
01:07
This is an animal preparation,
but shows kind of a normal left
ventricle that's the thicker pink
and shows the right ventricle,
which is the thinner pink.
01:14
And then the white areas in between
are the chambers of the heart.
01:18
If you banned the aorta, if you put
a little string around the aorta,
you basically
cause hypertension.
01:26
In this model, and as a result of
that, the muscles cells get bigger,
they have to pump against
a higher pressure,
and you get thickening
of the ventricle.
01:35
If I subsequently release that little
ligature, take the noose off the aorta.
01:40
Then that muscle will revert,
so it's basically hypertrophy
is a reversible process.
01:45
You build up extra protein and
you could break it back down,
using the things we talked
about that cause atrophy.
01:53
Proteasome, autophagy.
01:57
And I've mentioned this previously and is
just another good example of hypertrophy.
02:01
On the left hand side, you see a
woman who is very clearly pregnant
and the uterus has increased
dramatically in volume and size
over the course
of the pregnancy.
02:14
There are not a
whole lot more cells.
02:17
In fact, the vast majority of
the size change in this uterus
from pre-pregnant to end of
pregnancy is in the size.
02:26
So there's massive hypertrophy.
02:27
And that's all well and good,
because once the baby is delivered,
those cells will revert back to
their normal size and the uterus
gets back down to
its normal size.
02:37
All right, so we've had
atrophy and hypertrophy.
02:39
Let's talk about hyperplasia.