Hi. In this video, we're going to be talking about the extracellular matrix. The extracellular matrix is essentially everything outside of a cell. Whether it's a group of cells, a single cell, or tissue, all the components that are sitting next to but not part of the cells constitute the extracellular matrix. Why do we have this, and what is it made up of? It provides support to the cells. Why would they stick together? Some cells have individual proteins that can attach to others, but for the most part, you need something else, like the extracellular matrix, to group these cells and bind them together. It is made up of various fibers and proteins that connect things and provide support and structure to a group of cells that would otherwise just casually associate with each other. These connections lend strength to the cellular structure.
So, what are some of the fibers in the extracellular matrix? A significant component is collagen fibers. These fibers form connective tissues, which are discussed in other biology classes and are critical if you ever take anatomy. They are composed of collagen, which is produced by a specific cell type known as fibroblasts. These fibroblasts produce collagen that forms fibrils, connecting cells together and forming robust tissues. Another key component is elastin, a protein that provides elasticity, which is essential for tissues requiring flexibility, such as our skin. It prevents our skin from flaking off and breaking when pinched, indicating the importance of elastin in the extracellular matrix. Additionally, fibronectins, which are glycoproteins composed of sugars and proteins, connect collagen fibrils to the cells.
Another component to be aware of is GAGs (glycosaminoglycans), which are carbohydrates that also play a role in binding components within the extracellular matrix. One particular GAG to note is hyaluronan, which helps fill up space and provides consistency to the extracellular matrix. The extracellular matrix is essentially a network of different fibers that connect cells together, providing support and structure. In the extracellular matrix, you can envision a framework where cells are embedded within connective tissues, with fibers and cells interconnected, forming a cohesive unit.
Another extremely important protein in this context is integrins. Integrins are transmembrane proteins, meaning they extend through the cell membrane. These proteins are not just alongside the cells but are part of the cellular structure, attaching the extracellular matrix to the cytoskeleton of the cell. Integrins are composed of two alpha and two beta subunits and have active and inactive conformations. Here, you can envision an active integrin as extended upwards, interacting with the extracellular matrix and connecting it to the cell. In contrast, the inactive form is bent over, not engaging with anything. This dynamic state of integrins is crucial during the anchorage-dependent growth, where the cell's ability to grow is dependent on its attachment through integrins. This attachment is vital for tissue growth, and integrins also play a crucial role in signaling, ensuring communication within the extracellular matrix and facilitating cellular responses necessary for growth, proliferation, and survival. So, with that, let's move on.
