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Cell Junctions

Cell junctions, the connectors between cells, come in three major types: tight junctions, desmosomes, and gap junctions. Tight junctions create a watertight seal, blocking water and ions, while desmosomes allow for some flow between cells. Gap junctions, on the other hand, act like tunnels for water and ions, especially in cells that propagate electrical signals. Created by William Tsai.

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  • piceratops ultimate style avatar for user Professor Khan
    This guy is a really good teacher! But what is a spot weld?
    (26 votes)
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  • duskpin tree style avatar for user Sarahv
    please can u explain....Hemidesmosomes, intermediate junctions, intercellular bridges, interdigitation?
    (15 votes)
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  • blobby green style avatar for user Cyril Patra
    Do desmosomes relate to the sweat glands in the skin?
    (8 votes)
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    • leafers tree style avatar for user drzulu
      In a sense, yes. Desmosomes hold cells together that really do not want to break apart. An example is the "cardiac myocyte" muscle cells of the heart - holding onto each other so the heart doesn't break under all the pressure being exerted on its walls.
      Another common place to find desmosome connections is between our epithelial cells - we find an abundance of these in our skin. Desmosomes are made of keratin, the toughest substance in our bodies - so we have them to thank for keeping our skin together!

      In answer to your question - the only relationship that desmosomes have to sweat glands, is that they bind the epithelial cells that surround these glands. The glands themselves have conduits, or spaces between cells, for the emission of sweat.
      (8 votes)
  • leaf green style avatar for user david  Ilowitz
    you only spoke about desmosomes, what are Hemidesmosomes?
    (7 votes)
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  • hopper jumping style avatar for user Lucas De Oliveira
    Are these cell junctions , in general, more or less fixed ( it means stable)?? Has every cell a kind of junction or are there cells without it? How a junction interferes in the dissemination of cancer cells through the body?
    (3 votes)
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    • female robot ada style avatar for user Reine Fowajuh
      Yes, cell junctions are stable otherwise skin wouldn't always sweat... unless there's a main cause. And yes, there are cells without cell junctions, such as blood cells or other cells which move freely within the body. As for the last question, interference by junctions vary based on the cell type, cancer type, and host(individual).
      (2 votes)
  • aqualine ultimate style avatar for user Samara
    What is the role of gap junctions in neuronal tissue, specifically?
    If the gap junction 'tunnels' can be used to spread action potential from cell to cell, and are used in nerve cells, do the neurons have gap junctions connecting axon terminals to dendrites of other cells? The models of the neuron that I have seen display neurotransmitters being sent into an open synapse, their eventual reception being the way action potential is transferred to the post-synaptic cell.
    (3 votes)
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    • piceratops tree style avatar for user J. M. Williams
      Gap junctions are used for instantaneous transmission of AP from one cell to another. It is a quicker form used for things like cardiac muscle were transmission need to be immediate so the muscle can beat in unison for efficient pumping.
      As for synapse neuronal model that is likely from a desmosomes junctions.
      (2 votes)
  • aqualine tree style avatar for user Leonie Dupuis
    I recently read about an adherens junction in one of my practice passages.... Do adherens junctions fall under any of these categories? Or are they their own category of cell junction? Or perhaps, are they not cell junctions at all?
    (2 votes)
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    • aqualine tree style avatar for user Evan
      Intercellular junctions are divided into Occludens (tight) junctions, Adherens junctions, Nexus (Gap) junctions.
      Types of Occludens (tight) junctions:
      1. Zonula Occludens: between epithelial cells
      2. Occluding junction: Renal tubules
      3. Fascia occludens: endothelium of blood vessels
      ___ Types of Adherens junctions:
      1. Zonula Adherens: lies beneath Zonula Occludens
      2. Macula Adherens (Desmosomes)
      3. Hemidesmosomes: between epithelial cells and their basement membrane
      So basically, desmosomes are a type of Adherens junctions
      (3 votes)
  • blobby green style avatar for user Jaygee

    What is the meaning of stress in these scenarios. ( skin and intestine).
    Why do these organs experience more stress and in what way.
    (2 votes)
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  • duskpin ultimate style avatar for user tanvi
    are all cells connected.what makes the tunnels in gap junction
    (1 vote)
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  • aqualine ultimate style avatar for user noa
    could you please explain what are brush border membrane and basolateral membrane?
    (1 vote)
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Video transcript

Voiceover: In this video we're gonna talk a little bit about cell junctions. Cell junctions are basically things that connect cells to other cells. And they often occur in epithelial tissue. We're gonna talk about three major types of cell junctions today. The first, tight junctions, the second desmosomes, and the third, gap junctions. So starting off with tight junctions. Let's say we have two cells like this. So tight junctions basically connect the two cells together. And it's kinda like a glue that connects them together really tightly like that. I think of it like a watertight seal. It's a complete fluid barrier, which means that if there's water or ions or other molecules trying to get through between the two cells, they would not be able to. So it blocks out pretty much everything, from both sides of the cells, so water and ions cannot go through that gap between the two cells. This tight junction, this watertight seal tends to occur in things like the bladder, for example. Or sometimes intestines and the kidney. They occur in places where water really cannot go to other places. For example, our bladder holds urine, which is waste, and it would be really bad for our body if our bladder was unable to be watertight, to hold that urine just within the bladder. The next type that we're gonna talk about are desmosomes. Now let's say we have again, two cells like this. What desmosomes do, is I'm exaggerating the gap between these a little bit, but they're kinda like connections that hold two cells together. And these connections actually attach inside the cytoskeleton. And again, this gap is exaggerated. Usually the cells are a little closer. But in desmosomes, if there is water or ions, they can actually flow between these cells. So ions like sodium or potassium or water, or other small molecules can actually come through in this gap. I like to think about desmosomes kinda like spot welds They kinda hold the two cells together, but it's not like a complete glued seal like the tight junctions. They're kind of spotted throughout the cell so that things can actually flow in between the cells. Desomosomes tend to occur in tissues that experience a lot of stress. They offer a little bit of space for stress relief. So these spot welds, these desmosomes can be found in our skin and in our intestines. Now you notice that our intestines actually have both desmosomes and tight junctions. These cell junctions can be scattered throughout the even the same type of cell. So intestinal tissue can have both tight junctions and desmosomes. The last one we're gonna talk about are gap junctions. So let's say we have, again, our two cells like this. Gap junctions, and again I'm exaggerating the size of our gap junction. But, they're kinda like a tunnel that actually exists between the cells. So they're like a tunnel. And what they do is they actually let water and ions and so on, flow through this gap between the two cells. So they're kinda like a tunnel. These are often found in cells or tissue that spread action potential, or cells that use electrical coupling. For example, they can be found in cardiac muscle. This allows our cardiac muscle to actually spread action potential by using these ions. This allows our heart to continue beating. It can also be found in neurons. So in summary, we have three main types of cell junctions. The first are tight junctions. These are a watertight seal which prevents water or ions from flowing in between cells. We have desmosomes which are spot welds. And these spot welds generally occur in areas of stress, and they also allow water, ions, and other small molecules to flow between cells. And lastly are gap junctions. And gap junctions are tunnels that kind of connect two cells. And these tend to occur in cells that require propagation of electrical signal.