In this video, we're going to review the three different types of dense connective tissues. Since this video serves as a review, there's no new information covered that we haven't already discussed in our previous lessons. Therefore, if you're already confident about dense connective tissues, you can skip this video. However, if you need a refresher, stick around as this video could be beneficial for you. Below, we have a table listing the different types of dense connective tissues.
Notice the first column lists the particular type, the second column covers some key characteristics, the third column describes important functions, and the fourth column provides example locations where these tissues can be found in the body. It's key to remember that all dense connective tissues will have densely packed protein fibers in their extracellular matrix. We initially discussed the first type, dense regular connective tissue, which is characterized by a regular or parallel arrangement of the collagen fibers in the extracellular matrix, predominated by collagen fibers. Despite having a few elastic fibers, collagen is the main component. These fibers are designed to be strong, yet they offer some flexibility as well. Dense regular connective tissue lacks adipocytes or fat cells and migratory immune cells and is poorly vascularized, meaning it has few blood vessels. This trait is common to all dense connective tissues, contributing to their slow healing process.
The provided micrograph shows the densely packed collagen fibers in a parallel or regular arrangement, with a slight waviness that allows for some flexibility. However, once these fibers straighten, their strength is pronounced, as they offer little stretch once aligned. Functionally, because the parallel collagen fibers work together in one direction, they provide significant strength but specifically in the direction of the fibers' alignment, either from right to left or left to right. Example locations for dense regular connective tissue include forming ligaments, connecting bones to bones; tendons, connecting muscles to bones; and fascia, wrapping around muscles.
The next type we covered is dense irregular connective tissue, structurally similar to dense regular connective tissue but with protein fibers in an irregular or random arrangement. Like its counterpart, it is predominantly made of collagen fibers that provide strength. However, the random arrangement allows for strength in multiple directions, enhancing its ability to resist forces from various angles. Dense irregular connective tissue can be found beneath areolar tissue in the skin, wrapping joints, organs, and bones, helping to prevent tearing by resisting multidirectional forces. This tissue type's random fiber arrangement is what allows products like leather, derived from the dermis of animal skins, to be so durable.
Lastly, we reiterate our discussion on elastic connective tissue, sometimes categorized as a subtype of dense regular connective tissue due to its regular or parallel fiber arrangement. The primary difference is that elastic connective tissue contains a high proportion of elastic fibers, which outnumber the collagen fibers. Elastic fibers provide the ability for tissues to stretch extensively and then return to their original shape. This quality is essential for body structures requiring flexibility to bend, expand, and retract. Elastic connective tissue is found in the walls of arteries, such as the aorta, respiratory passageways including the trachea and bronchial tubes, and in the ligaments of our spine, accommodating movement and flexibility.
This concludes our review of dense connective tissues. Moving forward, we will apply these concepts and then explore specialized connective tissues. I'll see you all in our next video.