Introduction to Tissues & Histology - Online Tutor, Practice Problems & Exam Prep

Intro to Human Tissues

Hi, everyone. In this video, we're going to begin our introduction to tissues and histology. And so we already know that the human body is amazingly complex. I mean, just look at us. We've got trillions of cells and hundreds of different cell types. However, despite all of this amazing complexity, the human body is only built from just 4 primary types of tissue or 4 main types of tissue. And so 4 is a pretty manageable number, not too bad. And so in this video, we're only going to briefly introduce these 4 primary types of tissues in this illustration down below. But as we move forward in our course, we'll talk about each of these 4 primary types of tissues in a lot more detail, covering their characteristics, including their structures and their functions. And so before we actually introduce these 4 primary types of tissues, let's first recall from some of our previous lesson videos what the term tissues even means. And so recall from those previous lesson videos that the term tissues can be defined as groups of similar cells that are working together to perform related functions. And so it's important to note that the cells within a particular tissue are going to be similar in nature, but not necessarily identical. And it's also important to note that the term tissues itself, in addition to referring to the groups of cells, can also include the extracellular matrix or the ECM for short, which can be briefly defined as the surrounding material immediately outside of the cells. And so moving forward in our course, we're going to talk more details about the composition of the extracellular matrix. But for now, in this video, the bigger takeaway that I'd like you to walk away with is that the term tissues can be defined as not just the groups of similar cells, but also their extracellular matrix. Now, it's also important to note that all 4 of the primary types of tissues have an extracellular matrix. Although, the extracellular matrix can be more prominent in some types of tissues versus other types. But those are some details that we'll get to talk more about as we move forward in our course. But for now let's take a look at our illustration down below where we can finally introduce the 4 primary types of tissue. And so the first primary type of tissue that we're going to cover is epithelial tissue. An epithelial tissue is going to be important for covering surfaces, lining cavities, and forming glands. And so over here we have a micrograph of some epithelial tissue. Now the next type of tissue is going to be connective tissue. And connective tissue is actually the most abundant tissue throughout the human body, and it's the most diverse tissue in terms of its structure and its function. And connective tissue is also going to have the most prominent extracellular matrix. And so here we have a micrograph of some connective tissue. Now, the third type of tissue is going to be muscle tissue. And so as you probably already know, muscle tissue is going to be important for contracting in order to allow for body movements. And then last but not least, our 4th type of primary tissue is going to be nervous tissue. And nervous tissue is going to be important for detecting stimuli in our environment and transmitting electrical signals. And so once again, this is just a brief introduction to these 4 primary types of tissues. And as we move forward in our course, we'll get to talk a lot more details about them. And so we'll also get to define what the term histology means in one of our next videos. And so this concludes this video, and I'll see you all in our next video to get some practice.

Which of the following statements is true?

• A. Human body has trillions of cells operating completely independently of one another. 
• B. All organisms are composed of a unique combination of just four different tissue types. 
• C. The ECM is a combination of complex molecules found inside connective tissue cells. 
• D. "Tissues' can be used to refer not only to coordinating groups of similar cells but also to their ECM.

What is Histology?

In this video, we're going to focus on the study of tissues. And so the term histology is actually a term that means the study of tissues. More specifically, the term histology can be defined as the scientific study of tissue structure and function. And so this is going to include studying the shape, size, and arrangement of the overall tissue, but also of the individual cells within the tissue. And it's also going to include studying the ECM or the extracellular matrix, which, recall from our last lesson video, refers to the surrounding material immediately outside of the cells.

Now, what's really interesting to keep in mind is that when tissues are prepared for microscopy, generally, those tissues are going to appear transparent or clear under a microscope before being stained with dyes. And so that's exactly what this illustration down below is trying to emphasize. And so notice on the far left over here we're showing you a glass slide with a little bit of tissue sample on it. And if we zoom into that tissue sample as you see right here, you'll notice that initially the tissue is going to be unstained and appear transparent or clear under the microscope. And so that's going to make it very difficult to study the tissue because the poor contrast makes it difficult to visualize the structures. However, if we add a little bit of dye to our tissue, you'll notice that we can get some stained tissue. And notice that the stained tissue over here on the right is going to be a lot easier to study, a lot easier to visualize the structures because the contrast is significantly improved. And so that makes it a lot easier for the scientists over here to study the tissue.

Now moving forward throughout our course, we're going to be showing you a lot of different micrographs or images of tissues under the microscope. And what you'll notice is that many of those micrographs, or most of them, are going to be stained. And so that's something important to keep in mind as we move forward in our course. And also, by switching the type of dye that's being used, you can change the color of the staining. And so, here what we have is some kind of pinkish staining, but if you were to use a different type of dye, you could get a bluish staining or a different colored stain. And so this here concludes our brief lesson here on the study of tissues and histology. And we'll be able to get some practice applying some of these concepts in our next video. So I'll see you all there.

Which of the following is something that a histologist would NOT be expected to do?

• A. Utilize a light microscope to inspect a biopsy of suspected cancerous tissue to detect cellular abnormalities.  
• B. Prepare a sample of lung tissue using the Gram stain technique to identify presence of bacteria. 
• C. Conducting a cardiac tissue bypass surgery to replace damaged tissue & restore normal blood flow to heart.  
• D. Analyze cellular structure & ECM of a bone biopsy to help in diagnosis of osteoporosis. 

Map of the Lesson on Tissues

In this video, we're going to introduce our map of the lesson on tissues, which is down below right here. And so once again, this image represents our map of the lesson. Essentially, a table of contents that reflects how our lesson is built and what you can expect to see in our video lessons moving forward. And so because this image does represent our map of the lesson, you can pretty much use this image like a map to help continuously guide you through our lessons on tissues.

For example, we are currently in the topic, introduction to tissues and histology, which is being represented in our map at the very top right here. As we move forward in our course, we're going to be following this map from a top to bottom approach, but also from a left to right approach. After the introduction to tissues and histology, we'll then shift into tissue development for all four primary types of tissue. Then we'll talk about all 4 primary types of tissues in a lot more detail. Going from left to right here in order, starting with epithelial tissue, then connective tissue, then muscle tissue, and then finally ending with nervous tissue. One thing that you should note is that in this particular chapter, we're going to be covering epithelial tissue and connective tissue in a lot more detail than we're going to cover muscle tissue and nervous tissue. The reason for that is because Muscle Tissue and Nervous Tissue are going to have their own separate chapters with a lot more videos later in our course.

This particular chapter, once again, is going to be mainly focused on epithelial and connective tissue. With epithelial tissue, we'll talk about the functions of epithelial tissue and how it can be grouped into covering and lining epithelia and glandular epithelia. We'll talk about the structures of epithelial tissue including the differences between simple and stratified epithelial tissue. Then we'll go back up to glandular epithelial tissue, distinguishing between exocrine and endocrine glands, unicellular versus multicellular glands, and the different modes of secretion here, merocrine, holocrine, and apocrine.

After epithelial tissue, we'll talk about connective tissue, distinguishing connective tissue proper from specialized connective tissue. We'll talk about loose connective tissue and its 3 subtypes, areolar, reticular, and adipose. We'll also talk about dense connective tissue including regular, irregular, and elastic tissue. We'll talk about specialized connective tissues including cartilage and the 3 types of cartilage: hyaline, fibrocartilage, and elastic. We'll talk about bones, and we'll talk about blood and lymph.

After talking about connective tissue, once again, we'll move into muscle tissue, distinguishing between skeletal, cardiac, and smooth muscle tissue. And then finally, we'll talk about nervous tissue, including neurons and neuroglia. After we cover each of the 4 primary types of tissues, then we'll move on to talk about how membranes support and separate the body. And then finally, we'll wrap up with tissue repair.

Once again, this here is our map of the lesson on our lesson on tissues. And you can use this image like a map, essentially a table of contents. I'll be able to see you all in our next video to talk more about tissue development. I'll see you all there.