in this video we're going to discuss intercellular junctions um before we do that just a reminder that those intercellular junctions are formed by proteins so in the plasma membrane we have embedded proteins and they have multiple functions one of them is to create these connections between cells as they come together in tissues so there are three types of junctions that we're going to discuss uh we're going to start with tight junctions here and i have some diagrams to kind of try to help um represent the differences between them um so if we look at the tight junction and by the way think about the name tight um in a tight junction we have proteins from two adjacent cells right so you can kind of see those brown circles here and this proteins fuse together right so this is cell one this is cell two the protein from cell one fuses with protein in cell two same thing happens to the protein in here and tight junctions are perfect because they actually form an impermeable theory so impermeable theory what that means is that now these two cells are so close to each other that solutes are not able to pass between the cells okay and this is really important for the lining uh oberylia function that comes in epithelial tissues in particular right so this barrier aligning function is very important for epithelial tissues that's where we see a lot of tight junctions so let me give you a couple of examples we see thai junctions in the skin we see high junctions in the digestive system so think um stomach for example where thai junctions prevent the seepage of hydrochloric acid between the epithelial cells so it prevents the stomach from actually damaging itself and those tight junctions connect the cells so close together that they kind of look like a zipper so a lot of times uh in discussing tight junctions this analogy is made to the zipper let's look at desmosome so with desmosomes we again have proteins and these proteins now though have a fibrous appearance right so it's kind of like a thread so we have a two proteins here so that's one protein and that's another so two adjacent cells and i'll have some space in here so we can see what happens with fibrous proteins so um let me just write as a mind of fibrous proteins and these fibrous proteins almost look like they are sewing those cells together right so they expand from one protein to another in between cells but then they keep going through the entire cell get to the next side of the cell where we have a protein passes to the uh so cell 1 cell 2 cell 3 and if you're noticing it's kind of keeping all those cells together so that's actually the primary function of desmosomes is anchoring cells um so that gives us resistance against different types of forces that are applied to the tissue so uh one place where desmosomes are important is skin and hard and let me explain why that becomes important so in the heart we develop a lot of force when the heart contracts to pump blood out into blood vessels if it wasn't for desmosomes those cells would fall apart right because there is so much force it would make them fall apart from each other the desmosomes keep them together so for um a lot of reasons like that desmosomes are called mechanical junctions right they are keeping cells together and they will be best in the skin and heart again with the heart we already discussed them in the skin similar thing the last one is a gap junction and what's happening in the gap junction proteins in the plasma membrane of each cell form pores in like an opening and these pores connect to each other right so then if we have cell one and cell two solutes from cell one can pass through these pores directly into cell two it doesn't have to cross through the plasma membrane of two cells it actually gives buys us time valuable time so it allows cells to communicate communication and for that reason gap junctions are called communicating junctions um gap junctions are particularly important in the heart so you're noticing that the heart can have multiple junctions and in the heart due to gap junctions heart cells can talk to each other very quickly they are able to receive electrical signal almost at the same time so they can contract in unison they can contract at the same time so we've discussed the three inter cellular junctions a lot of times students feel like they're all called junctions that means they have same functions but that is not true each of these junctions has a very specific role to play within the human body