Video: What is an organ?

Hello everyone! Welcome to this anatomy tutorial. My name is Joao, and today, we’re going to be answering one of those questions that seemed really easy to answer, but might not be so simple. But, first, we’re going to be looking at this image – this beautiful image here – where you see different organs in your body. To just say that the word “organ” is one of those words that become part of your vocabulary as soon as you start learning sciences in school, even middle school or even elementary school. Some schools already mention the word “organ” in sciences. Then later when you take an anatomy course, you will be hearing the word “organ” again and again. Not to mention whenever you connect it to other structures or to other terms such as the stomach that you see here, the liver, and the heart – just to name a few of the organs that you can see here.

But if I ask you right now what is the definition of organ would you be able to tell me? Well, this is one of those questions that instructors like to throw at us even though they know that we’ve been doing anatomy for some time, but the formal definition of organ is something that we might not be so sure about. So, no worries, in this tutorial, I will be able to help you answer this question.

Even though it seems really quite simple and straightforward to answer, for instance, when someone asks you what an organ is, you might immediately picture what you see on the image – an instrument. But this is not what we’re going to be talking about. We will be talking about the organs that help us or help your body function properly. These powerful machines that are able to keep us alive.

But let’s get down to the official description of what constitutes an organ. And to do so, right here on the screen, you see a tissue. So when we look up the word “organ” in the dictionary, it is described as a group of tissues in the living organism that have been adapted to perform a specific function. Now, this is how you describe it – the official description, let’s say. Now, by this definition, we can quickly agree on what we already recognize as being an organ.

So, again, back to the screen. What you see here is known as a tissue. So a different collection of cells as you can see. All of these little cells here together also performing – they get-together to perform a certain function. This is what it would look like – a tissue would like if we look at it under a microscope – a light microscope.

Now these tissues join forces and work together so that they can be considered as what we know as an organ. And I just took here an example of the first tissue that we see, which is tissue from the liver, and then together all these tissues form the organ that you see now on the screen.

Now many of the famous organs in the body include the heart as you can see here on this image, the liver, the kidneys as you can see also here a little bit of the right kidney; the large intestine, the small intestine, and so on. So, different organs that come together to as we already know.

But did you know that by this definition, the skin is also an organ? Oh yes! In fact, the skin is the largest organ of the human body – a very popular trivia question, I would say.

So now when you are asked a question, what is an organ, you know that it is a group of tissues that are joined together in a structural unit to perform a specific function or functions.

Now, let’s break it down a little bit further to deepen our understanding. So, we’ve said that an organ is a group of tissues but an organ may contain several different types of tissues. And a good example of this would be the stomach as you can see now on the screen which contains epithelial tissue, glandular tissue, and also muscular tissue. And each type of this tissue is made up of a particular type of cell.

Then organs can be further organized into an organ systems and these organ systems are comprised of groups of organs that carry out a particular function. For example, some of the organ systems of the human body include the nervous system; the digestive system even represented a little bit here with a stomach, the esophagus, and the liver, gallbladder, just to name a few of the organs that you see on the image; the respiratory system, and the reproductive system.

Now to conclude this tutorial, let’s go over what we have learned so far. But before I want to do a clarification just putting together everything that we just learned. As you remember, to get to the definition of organ, we need to start with what we see here on the screen. These structures here that are known individually as cells. Then cells will come together as you remember, to form what you see now on the screen a tissue. Different types of tissue come together to then perform a function and do or constitute what we know as an organ – and you see the different organs here that we just mentioned – and, finally, these organs come together to function as a family on what we call a system.

So, again, going in order from the smallest unit to the largest unit, we have cells and these specialized cells make up a tissue and a group of tissues that are joined together in a structural unit performing a particular function make up an organ and finally, these organs are further grouped into organ systems according to their function.