Advanced Pathophysiology

Introduction to pathology

Welcome. In this video, we will discuss some of the tenets and basic concepts of pathology. To start with, if we look at the Latin root of the word pathology, it comes from two words, logos and pathos. Logos means study and pathos means suffering. So in Latin, the word pathology means the study of suffering. So we will embark to study or to review some of the basic concepts of suffering. Some of the words that are used a lot in textbooks and by pathologists are as follows. We have here etiology, morphology, and pathogenesis. Etiology is the cause. So when they say, what is the etiology of diabetes? It's, what is the cause of diabetes. Morphology. You can view morphology or talk about morphology from a gross perspective or a microscopic perspective. A gross perspective refers to what is the tissue or what is the appearance of the sample or whatever they're talking about.

If from a naked eye point of view, or if I had it in my hand, or if it was on a tray, on a table, what's the gross appearance? What does it look like with a naked eye? Microscopic experiences or appearances, what does it look like under a microscope? How do I describe what I'm seeing if I'm looking at the tissue under a microscope? Pathogenesis refers to the mechanism. The mechanism of the process, or what are the steps? So, A equals B, or is converted to B, is converted to C, converted to D. So the pathogenesis of diabetes is first this, which leads to this, which leads to this, and then which leads to this or any disease. So, the pathogenesis, if we understand that correctly, the pathogenesis of any pathology is we're trying to figure out what are the steps.

And the goal of medicine is to figure this out and then put a treatment between A and B, or B and C, or C and D to hinder or stop progression. Or actually sometimes to even reverse. So if we had to reverse the disease, that would be the best case scenario. So, I want to talk a little bit about a concept that most of you are probably familiar with, but it's just good to review. Homeostasis. Some authors prefer to use homeodynamic rather than homeostasis. But homeostasis is, if I had a little cell here and I had the nucleus here and the DNA inside, and then I had a mitochondria over here, all the organelles, organelles is simply what's inside the cell. Homeostasis is every cell has a set standard or function, if you will. Its job is to perform a specific function.

And if you apply a stress to a cell, some kind of stress, whether it be chemical, physical, any kind of stress that will put pressure or push this cell to do one thing or another, homeostasis is the set standard of the function to take care of this stress and then return to its normal functioning. Homeostasis is an attempt for each cell to maintain a set standard or function. With that in mind, I want to review this picture here. So we have here a normal cell. Okay. And it is maintaining homeostasis or homeodynamic, depending on whatever you like to say. And if the cell is stressed or put pressure upon the cell to act in a certain way, the cell's going to adapt if it can. Okay? And it will adapt to that environment, to that stress. And there's four ways that it's talked about that the cell will adapt, and we'll discuss those later in some next videos.

If the cell has inability to adapt, if the cell can't adapt to the stress that's applied to it, the cell's going to be hurt, it's going to be injured somehow. And we'll talk about all the ways that cells can be injured or damaged. Another way that will lead to cell injury or the cell being damaged in some way is if there's some event that is injurious to the cell. For example, if I'm riding my bike and I fall off my bike and I slide on the cement, my skin cells are definitely going to be damaged. They cannot adapt to that kind of stress, that kind of pressure and force. So they're going to be damaged. I'm going to bleed and all kinds of stuff. So, that's definitely cell injury. By the way, this picture was taken from Robbins Basic Pathology 8th Edition, Kumar is the author. It's a great, great textbook. So, from the cell injury, the cell has three scenarios by which it can follow.

One is, if the damage to the cell is below a certain threshold, the cell can revert back. Or if it's a reversible cell injury, then the cell can revert back to its normal homeostasis. It can go back to homeostasis if it's below a certain threshold. Now, that threshold is different for every cell. And we'll talk about in the future. We don't know exactly where the thresholds are at. That's another point of medicine. If we understand where the threshold of reversible cell injury is, then we could be really good at saying, "Oh, well, you're past the point of no return. I'm sorry." Or we could say, "Oh yes, we have really good chances of helping you." So that's another reason why we're trying to understand where this threshold is at. But if you pass the point of no return, if you will, or the point of irreversibility, the cell will undergo a process of necrosis.

Now necrosis equals cell death. That's what necrosis is. So if we pass the point of no return ourselves we'll die. And we'll discuss the process of necrosis and how that process is different than apoptosis. Okay? My undergrad physiology professor loved the word apoptosis, and he always used to discuss and talk about apoptosis. So, apoptosis is cell death, but it's organized. The cell death, this is an organized processes, this is an unorganized process. And we'll talk about apoptosis. But some authors also talk about it as kind of a cell suicide or programmed cell death. This is just a clean way for a cell to get rid of itself or die out of the cell population. So, if the cell is injured, it can either go through apoptosis and kill itself in an organized manner if it's not good anymore, if it's not performing its proper function, then it will die out.

If the cell is damaged below this threshold, this point of irreversibility threshold, then it will revert back to homeostasis. If it passes this point of irreversibility, it will undergo the process of necrosis. And we'll talk about these processes in-depth later in other videos. Another option is you can undergo subcellular alterations. Now, this would be like changes in DNA. This little symbol triangle in science sometimes can mean changes or change. So, changes in the DNA are some examples of subcellular alterations. Each cell has its definite shape and there's structural proteins that kind of hold the shape of the cell. These structural chain proteins can be altered in some way. So the cell, instead of round, it may look like this or something.

Maybe you can have just changes in the cell structural proteins. You can have changes in the mitochondria, which will affect ATP. For those that don't know what ATP is, this is the currency of energy. So, like in the house we use watts or kilowatts when you get your power bill, they say, "You used X amount of kilowatts. That's how much energy you used." Well, in the cells, they use the energy of ATP. And I can make a video on ATP and how it's produced and where it's produced and all that. Maybe I'll do that in another video. But for now, ATP is just the energy currency, if you will, of each cell. So, we'll see you in the next video.