Cell Injury and Adaptation: Introduction

00:01 All right.

00:03 The next topic that we're going to talk about in regards to cell injury and death is how tissues and cells fight back.

00:10 They adapt to injury.

00:12 They don't just get hit and call it a day.

00:15 They do adapt.

00:18 Here's our road map.

00:19 We've previously talked about an overview.

00:22 We've talked about things that can cause injury and how those insults actually generate injury within cells and tissue.

00:32 And now we're gonna talk about how tissues and cells adapt injury rather than just die.

00:38 Remember our original kind of overview, where you have on the left hand side things living within a normal homeostatic world and normal levels of pH and oxygen and nutrition etc.

00:52 And then injury happens, and we get potentially increased or decreased activity.

00:59 That's adaptation to maintain cellular viability and to maintain the integrity of the total functioning of the organism.

01:08 So we're trying to maintain normal homeostasis.

01:11 An important point that we will touch on is that adaptation can be maladaptive.

01:19 And just as an example, let's say that we have hypertension and the heart has to pump higher at greater velocities with greater ATP use to generate higher pressures.

01:36 When that happens, the individual cells get bigger and bigger and bigger.

01:40 That's all they could do.

01:41 We cannot make more heart cells, but those bigger and bigger cells are not necessarily getting more and more and more blood supply.

01:47 The blood supply stays the same.

01:50 So that adaptation, at a certain point the cells get too big and the diffusion distance from the nearest capillary gets too short, and you have cells that become relatively ischemic or hypoxic.

02:03 And so that adaptation that initially maintains normal profusion of the body against higher pressure can become maladaptive over time and you can have heart failure.

02:15 All right, just a general, high level concept.

02:18 But let's get down a little bit more into the weeds.

02:22 We're gonna look at several adaptive changes.

02:26 Atrophy- cells getting smaller, tissues getting smaller.

02:30 We're gonna look at hypertrophy- cells getting bigger, tissues getting bigger Hyperplasia- cell number increasing.

02:39 Metaplasia- change of cell from one mature adult form to another one.

02:46 We'll talk about subcellular responses, things going on within individual cells and then we won't touch on dysplasia today.

02:55 But keep in mind that adaptive change might also involve things becoming potentially malignant because of the accumulation of additional mutations.

03:06 First, atrophy.