The topic for today is
the Etiologies of Injury.
How various mechanisms can cause
cell injury and cell death.
Here's the overall road map.
We had had in a previous
discussion and overview,
and we have many
other things to cover.
But right now, we're going to
talk about ideologies of injury.
How can we damage a cell or
how can we damage a tissue?
How can we damage
the entire body?
So that's where we're going
today, that's the main focus.
So there are many different
ways that we can be traumatized,
and we, I mean ourselves and
our tissues in our bodies.
One is hypoxia,
so this is low oxygen tension.
This is inadequate oxygen,
and it can happen by,
holding your breath, it can happen
by going to the top of Mount Everest.
There are many different ways to have
hypoxia, but low oxygen is important
because oxygen is the means by which we
do electron transport to generate ATP.
There's chemical injury.
Clearly, chemicals can be toxic,
but they are toxic in various ways
to the tissues, and we'll
discuss how it actually happens.
Infections can be
There can be lytic viral infections
that will completely rupture cells.
There can be various toxins
elaborated by certain microorganisms
that cause injury, so infection is a
big component of this overall sequence.
There's also the
So the immune response is great.
It protects us against
infection, that's why we have it.
But a little can
go a very long way,
and sometimes the immune response
can be injurious all by itself.
That is not just in the
case of autoimmune disease,
where the immune system turns on
us and thinks that we're foreign.
But also in the case of an
infection, response to an infection,
the immune system doesn't know
exactly when the microorganisms
have been removed from the playing
field, and they sometimes continued
to do their thing,
causing additional damage.
There's genetic injury,
so mutations or variations that may lead
to defective proteins or defective
pathways can clearly cause cell injury.
We have nutritional injury,
so actually, too much
or too little or
All of those can
cause cell injury.
injury, so trauma,
being shot, stabbed,
run over by a truck.
All of those can be injury as
clearly to multiple tissues.
And then there's
aging, so senescence.
When the various cells
and tissues don't
turn over in a completely perfect way
and we accumulate multiple little hits
and over that period of time we lose
the ability to regenerate perfectly.
And that's senescence.
Okay, so those are kind of,
eight of the major players that
cause, can cause cell injury.
We're going to
emphasize the first four
and talk a little bit more
in detail about those.