Transcription
Today we're starting the course in pathophysiology. One of the most important subjects that connects what you learned in normal physiology with clinical medicine. If normal physiology explains how the body is supposed to function, then pathophysiology explores what happens when that normal balance is disrupted.
Pathophysiology is not just a list of diseases. It's the science of the processes that led to the development of the disease, how it progresses, and how complications arise. And it's exactly these mechanisms that allow us to understand why a patient feels unwell, why symptoms appear, and why complications develop. That's why in clinical practice, doctors don't work only with diagnosis. They work with processes.
Take for example a patient with hypertension. It's not just a label of high blood pressure. It's a complex pathological chain involving the kidneys, blood vessels, hormones, and the autonomic nervous system. And if a doctor understands this chain, it becomes clear why the patient may eventually develop cardiac hypertrophy, renal failure or be at increased risk of a stroke.
So the central idea of today's lecture is this. Disease is a process and all processes begin at the cellular level. That means today we'll spend quite a bit of time talking about the cell. In the following lectures we'll move on to organs. Then the idea is simple. If we understand what's happening at the cellular level, we'll be able to understand everything that follows.
We'll begin with the basics. The definition of disease. This part of the lecture will involve quite a few definitions unfortunately, but I think many of them you already understand at least on a basic level. After that, we'll move on to cell injury and the body's response to harmful stimuli. So let's start with the concept of disease.
There are different ways to look at it. Clinicians see symptoms. Laboratory specialists observe changes in test results. Microbiologists in turn focus on pathogenic organisms. But regardless of the perspective, disease essentially means a disturbance in the body's function, something that disrupts homeostasis. In pathophysiology we understand disease as a dynamic process during which this homeostasis that normal internal balance I mentioned is disrupted and importantly disease is not static. It develops it progresses and it leads to consequences. At each of these stages, specific physiological mechanisms are taking place and these are exactly the mechanisms we aim to understand and explain.
Next, we come to ethiology. The study of the causes and conditions of disease. Here we distinguish several types of ethological factors. For example, infectious factors. All infectious diseases are caused by a specific pathogen which largely determines both the pathogenesis and later on the treatment. Then we have physical factors. For instance, radiation can cause DNA damage which in turn leads to mutations in our genetic code and over time this results in tissue damage. Chemical factors are another group. A classic example is alcohol which causes liver injury. This can initially lead to fatty liver disease and eventually progress to liver cerosis. Next are genetic factors, various inherited mutations and chromosomal abnormalities. If we talk about specific genes, a very typical example is the BRCA gene mutation which significantly increases the risk of breast cancer. That's a classic example often used in genetics teaching. We also have metabolic and nutritional factors, things like obesity, vitamin deficiencies or electrolyte imbalances. And finally, environmental factors, stress, smoking, pollution. Smoking in particular is a classic ethiological factor because it simultaneously induces oxidative stress, chronic inflammation and tissue metablasia. Now what is metiplasia? You'll find out in the next part of the lecture. But the key takeaway here is that eeology answers the question what caused the disease and that's only the first step.
Next we have pathogenesis. If ethology as I mentioned is the cause then pathogenesis is the chain of mechanisms that connects that cause to clinical manifestations. In other words, it's the process that takes us from point A to point B and then to point C until eventually we see symptoms. So the question here is what exactly happens in the body that leads to these symptoms? What are the specific steps along the way? As a simple example, I've included the pathogenesis of atherosclerosis, just one classical pathway. You don't need to memorize it for now, but uh you will need to memorize it either way afterwards when we talk about atheroscllerosis. But uh right now at this point, it's here to help you grasp the concept. But the key idea is this. Ethiology is only the first step. Everything that follows that entire cascade of events is pathogenesis and in fact this is exactly what we analyze in pathofysiology.
We should also mention complications of disease. These arise when the primary disease process triggers additional pathophysiological mechanisms. Very often complications can be more severe than the disease itself. For example, as you can see again with atherosclerosis, it can lead to thrombosis and ultimately myocardial infarction. Other examples include pneumonia, which can progress into sepsis, diabetes, which can lead to renal failure or blindness, and of course, many other diseases.
So, now we're gone over the key terms, and with that, we're ready to move deeper right into the cell.