Epithelium: Basement Membrane

00:01 Another very important structure to consider when we are talking about epithelium is the basement membrane. Here is an epithelial surface that happens to be pseudostratified, ciliate epithelium and is supported by a basement membrane, which appears quite thick here.

00:23 In other epithelia, it's often difficult to see. I am going to use the basement membrane only when I talk about epithelia. There is often confusion between the term basement membrane and the term basal lamina. Basement membrane really refers to the structure you see with the light microscope. Basal lamina is part of the structure you see using the electron microscope. This is actually another layer. You can see using the electron microscope called the reticular lamina. And the epithelial cells actually secrete components of the basal lamina, but connective tissue cells secrete components of the reticular lamina. And so in tissues like muscle and nerve, instead of using the word basal lamina, we use the word external lamina because the basal lamina usually only refers to the descrption of the epithelia at the electron microscope level. But I just tend to use the term basement membrane when referring to epithelia and when looking at this epithelia with the light microscope. And you can see listed there a number of very important functions of these basement membranes fulfilled in the body. I mentioned earlier that some epithelia contain a number of different sorts of cells and these cells have different functions. Here is an example of where epithelial cells have invaginated or grown down under the surface into the underlying connective tissue or lamina propria. And these cells become very specialized to the secretory cells or big glandular tissue and that is going to be a subject of the later lecture that I am going to present for you. So in summary, it is important you know how we name epiithelia. It is important you know the certain specializations on the surface of some epithelial cells, the sorts of ways and which cells are held together in epithelia and the way which they are anchored for the underlying basement membrane. It is important you understand also that the anchoring of the epithelium into the underlying connective tissue is done by desmosomes similar to macular adherens, but they're called hemidesmisomes.

03:13 So I hope you have enjoyed this lecture on epithelia. I hope you now appreciate what epithelia does in the body because you are going to use this as a way in which to identify different organs and different tissues of the body and the jobs these epithelia do. So thank you very much once again for listening to this lecture.