Function vs. Morphology of Cellular Injury

00:00 Okay, so we've done from reversible to irreversible.

00:05 Let's look at this in a slightly different way.

00:08 An important point as we looked down the microscope, we try to understand cell death, tissue death, organismal death.

00:17 Is that an injury? Well, very early lead to diminished self function.

00:23 The cell won't be dead, but it won't be functioning.

00:26 Good example of this.

00:27 In myocardium in the heart, if I have occlusion of a vessel and no blood getting to the distal heart, that heart won't die until 20 to 30 minutes of occlusion, so it will be still viable.

00:40 But it won't have enough ATP to beat, to have it's normal cell function within about a minute.

00:48 So self function is lost far sooner than cell death actually occurring.

00:55 So that's what you see when we have our initial cell injury.

00:59 There's an effect on cell function first, and then we start seeing cell death.

01:04 But interestingly, we know from experimental data, that cell death happens at a certain time frame, depending on the cell type etc.

01:14 But our ability to see it and to visualize it is delayed.

01:18 So if we look by electron microscopy, there's been cell death for an hour.

01:23 We can't see it until, there's been sufficient change in the cellular architecture for us to recognize by electron microscopy.

01:30 So that's the ultra structural change.

01:33 And by light microscopy, we may have to wait for six hours to go by before we can recognize cells is being dead.

01:41 And then, if we're holding a tissue in our hand, we know it's clearly dead.

01:45 But it may be difficult to recognize gross morphological changes for days.

01:52 So we have a lots of function very quickly cell death occurring thereafter.

01:56 But our ability to recognize it even as magical pathologists may be delayed because it takes time for the changes to occur.

02:04 So that may mean that a patient will die acutely of a myocardial infarct.

02:09 They have big time damage to the heart and it quits working and the cells were dead.

02:15 But we cannot demonstrate that even with our best assays, for you know, unless they live for six hours after the original insult.

02:27 So on this slide, kind of what we just said in diagramatic form, inwards functional changes, perceived morphological changes.

02:36 The morphological changes are seen with a time lag, and it's very dependent on the sensitivity of the assay method.

02:42 Electron microscopy versus light microscopy versus gross evaluation.

02:47 So minutes to hours, we can see changes at the ultra structural level.

02:52 But it may take hours to days to see it by the other mechanisms.

02:55 Okay, so that's kind of how we recognize it.

02:58 Let's look at some forms of cell death and how we know that cells are dead.