Cell Junctions

00:45:44
https://www.youtube.com/watch?v=gmlA8V2zMv4

الملخص

TLDRDans cette vidéo éducative sur les jonctions cellulaires, le présentateur explique les divers types de jonctions qui relient les cellules, tels que les jonctions serrées, les jonctions adhérentes, les desmosomes, les hémidesmosomes et les jonctions communicantes. Chacune de ces jonctions est discutée en détail, couvrant leur structure moléculaire et leur rôle fonctionnel. Les jonctions serrées agissent comme des barrières de diffusion, essentielles dans des régions comme la barrière hémato-encéphalique. Les jonctions adhérentes et les desmosomes résistent aux forces de cisaillement et d'étirement, se trouvant dans les tissus soumis à des tensions comme la peau, les poumons et les tissus cardiaques. Les hémidesmosomes attachent les cellules à la matrice extracellulaire. Les jonctions communicantes permettent la communication entre cellules via le passage d'ions et de molécules de signalisation. La vidéo aborde également les implications cliniques des défaillances de ces structures, telles que le développement du cancer lié aux mutations des cadhérines et les maladies auto-immunes comme le pemphigus vulgaire.

الوجبات الجاهزة

  • 🔗 Les jonctions serrées agissent comme des barrières de diffusion empêchant le mouvement à travers les cellules.
  • 🦠 Implication clinique des jonctions serrées dans la protection du système nerveux central via la barrière hémato-encéphalique.
  • 🔬 Les jonctions adhérentes aident à résister aux forces de cisaillement et sont essentielles dans les tissus soumis à l'étirement.
  • 🫀 Les desmosomes sont cruciaux pour le tissu cardiaque et aident à prévenir la séparation cellulaire sous pression.
  • 🧬 Hémidesmosomes connectent les cellules à la matrice extracellulaire.
  • 📞 Les jonctions communicantes permettent la communication cellulaire via le passage d'ions et de molécules de signalisation.
  • 🧪 Dysfonctionnement des cadhérines peut entraîner la métastase dans le cancer.
  • 💡 Les connexons, constitués de connexines, forment des canaux entre les cellules pour permettre la communication.
  • 🩺 Pemphigus vulgaire et pemphigoïde bulleuse illustrent les effets auto-immunes sur les jonctions.
  • 🫁 Importance des jonctions dans la structure et la fonction des tissus respiratoires, cardio-vasculaires et cutanés.

الجدول الزمني

  • 00:00:00 - 00:05:00

    Les ninja nerds introduisent les jonctions cellulaires, incitant à s'abonner pour plus d'informations détaillées disponibles sur leur site.

  • 00:05:00 - 00:10:00

    Présentation de Chegg comme ressource d'étude avec explication des outils disponibles sur leur plateforme.

  • 00:10:00 - 00:15:00

    Introduction aux jonctions cellule à cellule, expliquant brièvement leur fonction de maintien structurel.

  • 00:15:00 - 00:20:00

    Les types de jonctions cellulaires incluent jonctions serrées, d'adhérence et desmosomes, chacun ayant une fonction spécifique dans la structure cellulaire.

  • 00:20:00 - 00:25:00

    Explication des jonctions serrées avec leurs rôles dans la barrière de diffusion et exemples dans le corps humain.

  • 00:25:00 - 00:30:00

    Les jonctions d'adhérence sont détaillées pour leur résistance aux forces de cisaillement, présents dans divers tissus corporels.

  • 00:30:00 - 00:35:00

    Les desmosomes, avec leur résistance aux tensions, sont liés aux disques intercalaires en tissu cardiaque.

  • 00:35:00 - 00:40:00

    Présentation des hémidesmosomes, se concentrant sur leur connexion entre cellules et matrice extracellulaire.

  • 00:40:00 - 00:45:44

    Les jonctions gap permettent la communication intercellulaire, essentielles pour les tissus excitables comme muscles cardiaques et certains neurones.

اعرض المزيد

الخريطة الذهنية

فيديو أسئلة وأجوبة

  • Quels sont les principaux types de jonctions cellulaires abordés ?

    Les principaux types discutés sont les jonctions serrées, les jonctions adhérentes, les desmosomes, les hémidesmosomes et les jonctions communicantes.

  • Quel rôle jouent les jonctions serrées ?

    Les jonctions serrées agissent comme des barrières de diffusion empêchant le passage de molécules entre les cellules.

  • Quels tissus sont particulièrement dépendants des desmosomes ?

    Les tissus cardiaque et cutané sont particulièrement dépendants des desmosomes pour résister aux forces de cisaillement.

  • Quels sont les composants clés des jonctions adhérentes ?

    Les composants clés sont les cadhérines, dépendantes du calcium, qui aident à connecter les cellules entre elles.

  • Comment les jonctions communicantes facilitent-elles la communication cellulaire ?

    Elles permettent le passage d'ions et de molécules de signalisation, facilitant la communication directe entre cellules.

  • Quels sont les effets possibles d'un dysfonctionnement des jonctions cellulaires ?

    Cela peut entraîner des maladies comme le pemphigus vulgaire et même favoriser la métastase dans le contexte du cancer.

  • Quelle est la différence entre les desmosomes et les hémidesmosomes ?

    Les desmosomes relient les cellules entre elles, tandis que les hémidesmosomes connectent les cellules à la matrice extracellulaire.

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التمرير التلقائي:
  • 00:00:07
    what's up ninja nerds in this video
  • 00:00:08
    today we're going to be talking about
  • 00:00:09
    cell junctions but before we get started
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  • 00:02:19
    let's get into this video all right
  • 00:02:20
    ninjas let's talk about cell to cell
  • 00:02:22
    junctions really it's not that hard
  • 00:02:24
    right it's basically just little
  • 00:02:26
    adhesions that are forming between cells
  • 00:02:28
    and there's many different functions of
  • 00:02:30
    these cell to cell junctions obviously
  • 00:02:32
    if you had one cell here in one cell
  • 00:02:35
    here and we had just certain proteins
  • 00:02:37
    that were anchored between these maybe
  • 00:02:39
    it's to hold them together so that way
  • 00:02:41
    if there's any kind of shearing forces
  • 00:02:42
    or stretching or abrasive forces it can
  • 00:02:45
    resist the separation of those cells or
  • 00:02:48
    if you have ions that are trying to move
  • 00:02:50
    between the cells and you don't want
  • 00:02:52
    those certain things to move through it
  • 00:02:53
    can block that it can act as like a
  • 00:02:55
    diffusion barrier or
  • 00:02:57
    maybe you have little channels that
  • 00:02:59
    exist between these two cells and you
  • 00:03:01
    want the cells to communicate with one
  • 00:03:03
    another or last but not least you know
  • 00:03:05
    there's a structure here we have a cell
  • 00:03:07
    here we have a cell there's a structure
  • 00:03:09
    underneath these cells called a basal
  • 00:03:11
    lamina
  • 00:03:13
    and a basal lamina is actually a little
  • 00:03:15
    bit of connective tissue and we also
  • 00:03:17
    have a heat adhesion molecules that not
  • 00:03:19
    just connect cell to cell
  • 00:03:21
    but connect the cell to the
  • 00:03:23
    extracellular matrix or the basal lamina
  • 00:03:26
    and this is what makes up what's called
  • 00:03:27
    your basement membrane
  • 00:03:29
    in order for us to truly understand
  • 00:03:31
    cell-to-cell's junctions though we have
  • 00:03:33
    to really zoom in look at their
  • 00:03:35
    structure know the names of those
  • 00:03:36
    structures the significance of it what
  • 00:03:38
    these things are actually functionally
  • 00:03:40
    for
  • 00:03:41
    and know what happens if these things
  • 00:03:43
    are damaged or what clinical things are
  • 00:03:45
    important
  • 00:03:46
    so what i want us to do is actually want
  • 00:03:48
    to really zoom in
  • 00:03:50
    on this connection between the cells
  • 00:03:53
    blow that up and look at these cells in
  • 00:03:56
    a more zoomed in fashion and this is
  • 00:03:58
    what we're going to be pretty much
  • 00:04:00
    focusing on for the rest of this video
  • 00:04:02
    there is a couple different types of
  • 00:04:03
    cell to cell junctions and then cell
  • 00:04:05
    extracellular matrix or basal lamina
  • 00:04:07
    junction
  • 00:04:08
    the first one that we'll discuss is
  • 00:04:10
    called tight junctions and there's
  • 00:04:12
    proteins called occludings and claddins
  • 00:04:14
    and zone occludens all of these things
  • 00:04:16
    that we'll get into that that's the
  • 00:04:17
    first one
  • 00:04:19
    the second one that we'll talk about is
  • 00:04:20
    called the adherence junctions
  • 00:04:23
    and the third one that we'll talk about
  • 00:04:25
    is called your desmosomes
  • 00:04:28
    now what you guys will understand is
  • 00:04:29
    that tie junctions big thing to take
  • 00:04:31
    away from it is they're more of like a
  • 00:04:32
    diffusion barrier they block things from
  • 00:04:34
    moving between cells and help to hold
  • 00:04:35
    cells tightly together
  • 00:04:37
    adherence junctions are much stronger
  • 00:04:39
    than type junctions and they're really
  • 00:04:41
    good for shearing forces and abrasive
  • 00:04:43
    forces but you know desmosomes are the
  • 00:04:45
    most tough and really really high
  • 00:04:48
    tensile against high shearing forces a
  • 00:04:50
    lot of abrasive stretch
  • 00:04:53
    next thing is gap junctions and these
  • 00:04:54
    are good for cell to cell communication
  • 00:04:57
    and last but not least is what's called
  • 00:04:59
    your hemidesmosomes and these are what
  • 00:05:02
    connect cells
  • 00:05:04
    to the basal lamina or the extracellular
  • 00:05:06
    matrix so we have tight junctions at
  • 00:05:09
    hearings junctions desmosomes gap
  • 00:05:11
    junctions and hemidesmosomes let's talk
  • 00:05:13
    about each one of these individually
  • 00:05:14
    understand their structure understand
  • 00:05:16
    their function and understand the
  • 00:05:17
    clinical significance all right so the
  • 00:05:19
    first solid cell junction that we have
  • 00:05:20
    to talk about is called tight junctions
  • 00:05:21
    now tight junctions what i need you guys
  • 00:05:23
    to know i need to know the structure the
  • 00:05:24
    function and the clinical significance
  • 00:05:26
    okay so first thing about the structure
  • 00:05:29
    when we talk about these here's cell
  • 00:05:30
    number one let's actually let's call
  • 00:05:32
    this cell number one and this is cell
  • 00:05:34
    number two
  • 00:05:35
    and again we're just looking at the cell
  • 00:05:36
    membranes of cell number one and cell
  • 00:05:39
    number two and how these cell membranes
  • 00:05:41
    are actually joined together okay
  • 00:05:43
    because that's the point of the junction
  • 00:05:45
    that we have here this tight junction
  • 00:05:47
    there's two particular proteins that
  • 00:05:49
    come out from the cell membrane and
  • 00:05:52
    interact with one another in between the
  • 00:05:54
    space between these cells
  • 00:05:56
    and this per this pink protein up here
  • 00:05:59
    there's two types one is called clawdens
  • 00:06:02
    so you have what's called clawdens
  • 00:06:05
    and then the other one down here in this
  • 00:06:07
    purple color here is called occludens
  • 00:06:12
    so you have two particular proteins that
  • 00:06:14
    are basically spanning through the
  • 00:06:17
    extracellular
  • 00:06:18
    space and actually anchored into the
  • 00:06:20
    cell membrane of cell one and cell two
  • 00:06:22
    and again these proteins are called
  • 00:06:24
    claudines and occludens
  • 00:06:27
    now
  • 00:06:28
    on the inner cytosolic so this would be
  • 00:06:30
    on the cytosol side right so this is the
  • 00:06:31
    cell membrane this would be on the
  • 00:06:33
    cytosol this would be the extracellular
  • 00:06:34
    space
  • 00:06:36
    on the cytosolic side there's these
  • 00:06:37
    black proteins these black circular
  • 00:06:39
    proteins
  • 00:06:40
    these black circular proteins are called
  • 00:06:44
    zona
  • 00:06:46
    occludins
  • 00:06:48
    they're called zona occludings and
  • 00:06:50
    there's different types there's zo1
  • 00:06:51
    zo203
  • 00:06:53
    okay
  • 00:06:54
    so again you have spanning through the
  • 00:06:56
    cell membrane out into the extracellular
  • 00:06:58
    spaces the claudines and occludens they
  • 00:07:00
    connect with one another from cell one
  • 00:07:01
    to cell two on the cytosolic side you
  • 00:07:04
    have the zona occludens and they're
  • 00:07:06
    bound to that actual cludens and
  • 00:07:08
    claudin's proteins okay
  • 00:07:11
    then the last protein here on the inner
  • 00:07:14
    cytosolic side that are bound to the
  • 00:07:16
    zone occludens these kind of navy blue
  • 00:07:18
    ones here
  • 00:07:19
    these are called actin
  • 00:07:22
    filaments
  • 00:07:24
    they're called actin filaments
  • 00:07:26
    so there is again
  • 00:07:28
    knowing these proteins this is a very
  • 00:07:29
    important thing
  • 00:07:30
    because if they ask you on the test high
  • 00:07:32
    junctions
  • 00:07:33
    the actual part of the protein that
  • 00:07:35
    spans through the cell membrane out to
  • 00:07:36
    the extracellular component and attaches
  • 00:07:39
    cell to cell those are called
  • 00:07:41
    clawdens and occludens
  • 00:07:44
    the proteins on the cytosolic side that
  • 00:07:47
    is bound to those actual transmembrane
  • 00:07:50
    proteins the occludings and claudians is
  • 00:07:51
    called
  • 00:07:52
    zona occludens
  • 00:07:54
    and then the proteins that are bound on
  • 00:07:55
    the most inner cytosolic side to the
  • 00:07:57
    zona occludens are called the actin
  • 00:08:00
    filaments
  • 00:08:01
    now
  • 00:08:02
    why is this important
  • 00:08:04
    the significance of the tight junctions
  • 00:08:07
    is really within the name they tightly
  • 00:08:09
    hold the cells together
  • 00:08:12
    and the main focus of that is imagine
  • 00:08:14
    you have some type of like
  • 00:08:16
    sodium molecule or potassium molecule or
  • 00:08:19
    maybe you have some type of like protein
  • 00:08:22
    molecule that you don't want to be able
  • 00:08:24
    to
  • 00:08:25
    move
  • 00:08:26
    between these cells you want to block
  • 00:08:29
    that process
  • 00:08:30
    that is the function of these actual
  • 00:08:32
    tight junctions so their design is to
  • 00:08:35
    act as a diffusion barrier
  • 00:08:38
    and pretty much block
  • 00:08:40
    the transport of ions and different
  • 00:08:44
    types of large molecules between the
  • 00:08:46
    cells okay that's really it
  • 00:08:49
    what i really want to add on though
  • 00:08:51
    is imagine that we have two parts of the
  • 00:08:53
    cell right
  • 00:08:54
    so you have this part of the cell all
  • 00:08:56
    right let's imagine here i have this
  • 00:08:57
    blue
  • 00:08:58
    tissue here this remember this was
  • 00:08:59
    called the basal lamina
  • 00:09:01
    it was just underneath it's called the
  • 00:09:03
    it basically makes up whenever you have
  • 00:09:04
    the cell and then this basal lamina
  • 00:09:06
    makes up what's called the basement
  • 00:09:07
    membrane
  • 00:09:08
    this is the basal surface of the cell
  • 00:09:11
    this is the apical surface of the cell
  • 00:09:14
    tight junctions are mainly connecting
  • 00:09:17
    cell to cell
  • 00:09:18
    at the apical surface that's a very
  • 00:09:21
    important thing so another thing i need
  • 00:09:22
    you guys to remember is that they're
  • 00:09:24
    connected at what surface
  • 00:09:26
    the apical
  • 00:09:27
    surface
  • 00:09:29
    so they connect cell to cell at the
  • 00:09:31
    apical surface and they're primarily a
  • 00:09:33
    diffusion barrier for things like ions
  • 00:09:35
    and large molecules that's really it
  • 00:09:39
    now
  • 00:09:40
    what kind of locations would you want
  • 00:09:42
    these diffusion barriers where you want
  • 00:09:45
    to really kind of hold cells tightly
  • 00:09:46
    together and maybe block certain things
  • 00:09:48
    that you want to be able to move
  • 00:09:50
    not to be able to actually move between
  • 00:09:52
    the cells and get into a particular area
  • 00:09:54
    well i would think that one really
  • 00:09:56
    important one that you'd really really
  • 00:09:58
    want to be careful of
  • 00:10:00
    is your brain right you don't want just
  • 00:10:02
    proteins just moving wherever they want
  • 00:10:04
    in and out of the blood and into your
  • 00:10:06
    actual neural tissues so the blood-brain
  • 00:10:09
    barrier is definitely riddled with lots
  • 00:10:11
    of tight junctions so the blood
  • 00:10:14
    brain barrier would definitely be one
  • 00:10:16
    big one
  • 00:10:17
    so you know within the blood-brain
  • 00:10:18
    barrier you have these cells here this
  • 00:10:20
    is a capillary here this is a blood
  • 00:10:22
    vessel
  • 00:10:23
    and then this blue stuff is called the
  • 00:10:24
    basal lamina and then this third thing
  • 00:10:27
    is called your astrocytes right
  • 00:10:30
    so these three things are what make up
  • 00:10:31
    your blood-brain barrier
  • 00:10:33
    well these
  • 00:10:35
    uh kind of red cells are called
  • 00:10:37
    endothelial cells
  • 00:10:39
    and in between the endothelial cells you
  • 00:10:41
    see these these actual pink and purple
  • 00:10:43
    proteins those are called your tight
  • 00:10:45
    junctions so whenever you have molecules
  • 00:10:48
    that are running through here maybe you
  • 00:10:50
    have some type of like
  • 00:10:51
    amino acid or some type of protein
  • 00:10:54
    molecule that you don't want to be able
  • 00:10:56
    to get out into this area where the
  • 00:10:58
    neurons are at these actual proteins
  • 00:11:01
    will block that so that's their function
  • 00:11:03
    of it as a diffusion barrier so think
  • 00:11:05
    about blood-brain barrier
  • 00:11:06
    another one
  • 00:11:08
    is you know actually within our gi tract
  • 00:11:10
    our git is a really important one that i
  • 00:11:12
    want you guys to remember so two big
  • 00:11:14
    ones if you don't remember the other
  • 00:11:15
    ones please don't forget this one blood
  • 00:11:18
    brain barrier and git
  • 00:11:20
    the git we also have lots of these
  • 00:11:22
    little tight junctions near the apical
  • 00:11:24
    surface
  • 00:11:24
    because we also want to be able to again
  • 00:11:26
    prevent certain types of
  • 00:11:28
    pathogens certain types of molecules
  • 00:11:30
    that are in our gi tract from getting in
  • 00:11:33
    to the actual blood where things are
  • 00:11:35
    supposed to be absorbed
  • 00:11:37
    so we want to have tight junctions here
  • 00:11:39
    that control the movement of certain
  • 00:11:41
    types of molecules
  • 00:11:43
    from the actual lumen and into the
  • 00:11:45
    bloodstream
  • 00:11:47
    you know what else
  • 00:11:48
    is that especially in the stomach you
  • 00:11:51
    know the cells are tightly bound to one
  • 00:11:52
    another
  • 00:11:53
    if you have these cells that are tightly
  • 00:11:55
    bound to one another in the stomach
  • 00:11:57
    what's the stomach make a lot of
  • 00:11:59
    hydrochloric acid we want those cells to
  • 00:12:01
    be really tightly close to one because
  • 00:12:03
    if we have some separation between them
  • 00:12:05
    what can happen that hydrochloric acid
  • 00:12:06
    can seep in between those cells and
  • 00:12:09
    cause necrosive damage so it's also
  • 00:12:12
    really important to think about this
  • 00:12:14
    whenever you have these two cells within
  • 00:12:16
    the stomach you definitely want a really
  • 00:12:17
    tight connection because imagine if that
  • 00:12:20
    nasty hydrochloric acid was able to seep
  • 00:12:23
    between these it would cause destructive
  • 00:12:25
    lesions
  • 00:12:27
    so that's another thing so again it's
  • 00:12:28
    trying to prevent nasty molecules and
  • 00:12:30
    nasty proteins or pathogens from being
  • 00:12:32
    able to move from the lumen and into the
  • 00:12:35
    tissues or the blood around that actual
  • 00:12:37
    gi tract
  • 00:12:39
    other areas to think about
  • 00:12:41
    is your respiratory system obviously
  • 00:12:43
    within the respiratory tract
  • 00:12:45
    there's definitely going to be these
  • 00:12:48
    beautiful tight junctions
  • 00:12:50
    and there's actually a specialized tight
  • 00:12:52
    junctions we actually have to mention
  • 00:12:54
    this this might come up in your usmle is
  • 00:12:57
    that in the kidneys there's what's
  • 00:12:59
    called leaky i know it's weird but we
  • 00:13:02
    call them leaky junctions they're a sub
  • 00:13:05
    of tight junctions
  • 00:13:07
    and in the actual proximal convoluted
  • 00:13:09
    tubule is the specific place that i want
  • 00:13:12
    you guys to remember there's what's
  • 00:13:13
    called leaky junctions so if you imagine
  • 00:13:15
    you take kind of an uh a cell here and a
  • 00:13:18
    cell here and let's imagine this is a
  • 00:13:20
    part of the kidney tubules
  • 00:13:22
    these cells have these little leaky
  • 00:13:24
    junctions between them they're like
  • 00:13:26
    tight junctions but they allow for
  • 00:13:29
    certain types of ions to be able to pass
  • 00:13:31
    through things like potassium things
  • 00:13:32
    like chloride things like sodium and
  • 00:13:34
    water okay so that's a specialized tight
  • 00:13:37
    junction they're called leaky junctions
  • 00:13:39
    and they're found in the proximal
  • 00:13:41
    convoluted tubule of the kidneys so to
  • 00:13:43
    recap occludants claudines zona
  • 00:13:45
    occludens actin again apical surfaces
  • 00:13:49
    where these tight junctions are
  • 00:13:50
    connecting they're a diffusion barrier
  • 00:13:52
    big ones to remember is blood-brain
  • 00:13:53
    barrier
  • 00:13:54
    git
  • 00:13:55
    respiratory tract and again there's this
  • 00:13:58
    modified type called leaky junctions in
  • 00:14:00
    the kidney tubules why is all this
  • 00:14:02
    important why do we need to know this
  • 00:14:04
    here's why here's the clinical relevance
  • 00:14:06
    to it you know there's a nasty pathogen
  • 00:14:10
    okay two of them
  • 00:14:11
    one is called helicobacter
  • 00:14:14
    pylori you guys know this pathogen
  • 00:14:17
    and there's another one called
  • 00:14:19
    clostridium
  • 00:14:21
    difficile
  • 00:14:23
    these pathogens they release nasty types
  • 00:14:25
    of toxins you know what these toxins do
  • 00:14:29
    they cause destruction
  • 00:14:32
    of these tight junctions
  • 00:14:34
    if you destroy the tight junctions and
  • 00:14:35
    you form kind of a little space between
  • 00:14:37
    these
  • 00:14:39
    okay so now i can form like actual space
  • 00:14:41
    between these cells
  • 00:14:43
    i can now easily allow for certain types
  • 00:14:46
    of
  • 00:14:47
    things molecules whatever it may be
  • 00:14:49
    to be able to go in between these cells
  • 00:14:52
    a lot easier
  • 00:14:54
    in the stomach where h pylori likes to
  • 00:14:56
    stay
  • 00:14:57
    what would that do
  • 00:14:59
    if you actually got rid of the tight
  • 00:15:00
    junctions in this area
  • 00:15:03
    you would allow hydrochloric acid to
  • 00:15:04
    start eroding its way through and then
  • 00:15:06
    imagine what can happen if you start
  • 00:15:08
    having like that kind of process
  • 00:15:09
    happening
  • 00:15:10
    where you start forming these nasty
  • 00:15:12
    little things called
  • 00:15:14
    ulcers
  • 00:15:15
    so then the actual helicobacter pylori
  • 00:15:17
    again it can actually invade into these
  • 00:15:19
    areas
  • 00:15:20
    and what can this cause what is this
  • 00:15:21
    disease called this is called peptic
  • 00:15:23
    ulcer disease
  • 00:15:24
    so peptic
  • 00:15:26
    ulcer disease is the result of the h
  • 00:15:30
    pylori separating the tight junctions
  • 00:15:32
    within the stomach and allowing for the
  • 00:15:34
    acid to infiltrate in between causing
  • 00:15:36
    ulcers
  • 00:15:38
    c diff you guys know this one it's going
  • 00:15:40
    to infiltrate in between these actual
  • 00:15:42
    cells start separating them
  • 00:15:44
    and when you separate them what's going
  • 00:15:46
    to be able to leak out different things
  • 00:15:47
    like water and different ions and that's
  • 00:15:50
    going to cause lots of
  • 00:15:52
    diarrhea
  • 00:15:53
    and as a result if you get all of this
  • 00:15:55
    intense diarrhea
  • 00:15:57
    this is a infectious process called
  • 00:16:00
    clostridium difficile associated
  • 00:16:01
    diarrhea and that is due to the c diff
  • 00:16:04
    because again you're forming separation
  • 00:16:07
    between those cells and allowing for
  • 00:16:08
    things to now easily be able to get
  • 00:16:10
    pulled into the lumen of the gi tract
  • 00:16:13
    and plus more inflammatory molecules
  • 00:16:15
    like more pathogens can actually leak
  • 00:16:16
    into the bloodstream that way as well
  • 00:16:18
    so
  • 00:16:19
    you get the significance of type
  • 00:16:21
    junctions now
  • 00:16:22
    let's now move on to the next one which
  • 00:16:24
    is called the adherence junctions all
  • 00:16:25
    right so let's talk about the second
  • 00:16:27
    junction the adherence junctions the
  • 00:16:29
    adherence junctions are really cool so
  • 00:16:31
    when we talk about in comparison tight
  • 00:16:33
    junctions versus adherence junctions
  • 00:16:36
    these are more specifically what we're
  • 00:16:37
    going to talk about for more shearing
  • 00:16:39
    forces stretch being able to resist a
  • 00:16:41
    lot of high tensile types of abrasive
  • 00:16:44
    forces really
  • 00:16:46
    but in order to do that we have to know
  • 00:16:47
    the particular proteins that are
  • 00:16:49
    involved to help in that process so the
  • 00:16:51
    first component here is these blue
  • 00:16:53
    proteins and this is actually a really
  • 00:16:54
    important component here so these
  • 00:16:56
    proteins here are called
  • 00:16:59
    cadherins but we give them a special you
  • 00:17:01
    know number a little letter before we
  • 00:17:03
    call it e
  • 00:17:05
    cad adherence
  • 00:17:08
    so it's the extracellular component of
  • 00:17:10
    the catherine okay because the catherine
  • 00:17:12
    actually anchors into the cell membrane
  • 00:17:14
    and then you have the component of it
  • 00:17:15
    that actually is going to bulge out from
  • 00:17:18
    the cell membrane into the extracellular
  • 00:17:20
    space so this is an e-cad here and this
  • 00:17:22
    is an e-cad here and it actually it's
  • 00:17:24
    interesting is that they're both kind of
  • 00:17:25
    like homologous to one another they both
  • 00:17:27
    are pretty much the same type of
  • 00:17:29
    structure
  • 00:17:30
    now when we have this e-cad hearing and
  • 00:17:32
    this e-cad here and actually binding
  • 00:17:33
    with one another we have to have some
  • 00:17:35
    special molecule between them that
  • 00:17:38
    actually helps to really anchor them
  • 00:17:39
    together you know what that beautiful
  • 00:17:40
    molecule is that actually sits right in
  • 00:17:42
    this space here
  • 00:17:44
    good old calcium so once you have once
  • 00:17:46
    you remember here is cad hearings
  • 00:17:49
    anytime you see that word cad hearings
  • 00:17:52
    these are calcium dependent proteins
  • 00:17:55
    that's a big thing for your test cad
  • 00:17:57
    herons are calcium dependent proteins so
  • 00:18:00
    usually calcium acts as the bridge
  • 00:18:02
    between anchoring these two cadherins
  • 00:18:04
    together okay so that e-cadherins coming
  • 00:18:06
    from the cell membrane outwards into the
  • 00:18:08
    extracellular space binding with one
  • 00:18:10
    another via the process of calcium
  • 00:18:13
    the next protein which is actually going
  • 00:18:15
    to be on that inner cytosolic side of
  • 00:18:17
    the cell membrane is this purple protein
  • 00:18:20
    this purple protein here is called
  • 00:18:22
    vinculin
  • 00:18:25
    and then there's another one which is
  • 00:18:27
    this maroon color protein which is again
  • 00:18:30
    on the inner cytosolic side
  • 00:18:32
    and usually it's kind of like coupled
  • 00:18:34
    right next to the vein killing just for
  • 00:18:35
    simplicity's sake we put it right after
  • 00:18:37
    it but usually they're kind of like
  • 00:18:38
    around the same proximity with one
  • 00:18:40
    another and these are called the katinin
  • 00:18:42
    proteins and there's different types of
  • 00:18:44
    ketene and proteins okay so you have the
  • 00:18:47
    e-cadherins then you have the vinculin
  • 00:18:49
    and catenan proteins and then the last
  • 00:18:51
    part which is on the most inner
  • 00:18:53
    cytosolic side
  • 00:18:54
    is what's called your actin filaments
  • 00:18:57
    these are called your actin
  • 00:19:00
    filaments
  • 00:19:01
    so when someone says hey which types of
  • 00:19:03
    junctions contain actin filaments on
  • 00:19:05
    their most inner cytosolic side you can
  • 00:19:07
    say
  • 00:19:08
    tight junctions and adherence junctions
  • 00:19:10
    and you'll see later that even other
  • 00:19:12
    proteins as well but
  • 00:19:14
    that is the basic structure so from
  • 00:19:16
    extracellular side e-cadherins with
  • 00:19:18
    calcium then vinculin and katanan and
  • 00:19:20
    then actin filaments on the almost inner
  • 00:19:22
    part now because these have all of these
  • 00:19:26
    really important anchoring proteins
  • 00:19:28
    they're more for resisting a lot of
  • 00:19:29
    stretch
  • 00:19:30
    okay so when we talk about their
  • 00:19:32
    function if we have cell one here
  • 00:19:34
    and cell two
  • 00:19:36
    these are if you actually look compared
  • 00:19:37
    this is the apical surface so if i had
  • 00:19:39
    kind of that basal lamina again
  • 00:19:41
    this is the basal lamina here
  • 00:19:44
    this is the apical surface this is the
  • 00:19:46
    basal surface
  • 00:19:47
    these are usually a little bit more
  • 00:19:49
    basil so if we had to compare let's say
  • 00:19:51
    here's your tight junctions
  • 00:19:53
    it's going to be more basal in
  • 00:19:55
    comparison to the tight junctions so if
  • 00:19:57
    we were to put here for their actual
  • 00:19:59
    position of where they are they're more
  • 00:20:01
    basal
  • 00:20:04
    in comparison
  • 00:20:08
    two
  • 00:20:10
    tight junctions
  • 00:20:12
    okay beautiful that's one thing the
  • 00:20:15
    second thing that i really want you to
  • 00:20:16
    remember is tight junctions are more as
  • 00:20:17
    a diffusion barrier right they block
  • 00:20:19
    ions molecules large proteins things
  • 00:20:21
    from being able to move past them
  • 00:20:23
    between the cells
  • 00:20:24
    adherence junctions are more for
  • 00:20:27
    shearing
  • 00:20:30
    or abrasive forces
  • 00:20:33
    so any type of like thing where there's
  • 00:20:35
    a lot of stretching there's a lot of
  • 00:20:37
    rubbing
  • 00:20:38
    anything that's trying to separate cells
  • 00:20:40
    apart from one another this is their
  • 00:20:42
    design they're more designed to be able
  • 00:20:44
    to resist those shearing and abrasive
  • 00:20:47
    forces that is their design they're not
  • 00:20:49
    really a diffusion barrier they're more
  • 00:20:51
    resistant allowing for stretch okay
  • 00:20:53
    keeping those cells together
  • 00:20:55
    so
  • 00:20:56
    with that being said what type of
  • 00:20:58
    tissues would you really want to have
  • 00:21:00
    these kinds of junctions really anywhere
  • 00:21:02
    where there's tight junctions we have
  • 00:21:04
    adherence junctions they give a little
  • 00:21:05
    bit more of that ability to prevent the
  • 00:21:08
    cells from separating from one another
  • 00:21:10
    from intense types of stretch or
  • 00:21:12
    abrasion
  • 00:21:13
    what kind of things would that be well
  • 00:21:15
    your stomach and your gastrointestinal
  • 00:21:16
    tract have to accommodate
  • 00:21:18
    to food and fluids so they're going to
  • 00:21:20
    have to stretch they have to accommodate
  • 00:21:21
    to that so they'd be found within your
  • 00:21:24
    gastrointestinal tract so that'd be one
  • 00:21:26
    your git
  • 00:21:28
    the other thing is your epithelial
  • 00:21:30
    tissue
  • 00:21:31
    your epithelial tissue within your
  • 00:21:32
    respiratory tract your respiratory tract
  • 00:21:34
    may have to also undergo particular
  • 00:21:36
    dilation and constriction within your
  • 00:21:37
    bronchioles and so because that they
  • 00:21:40
    also have to not only have that process
  • 00:21:42
    but you know whenever your alveoli are
  • 00:21:44
    inflating they have to be able to
  • 00:21:45
    accommodate maybe a certain amount of
  • 00:21:46
    stretch or distensibility our lungs are
  • 00:21:48
    naturally compliant so we want the lungs
  • 00:21:50
    to be able to have some compliance and
  • 00:21:52
    ability to stretch whenever they're
  • 00:21:53
    being inflated versus whenever they're
  • 00:21:55
    actually exhaling and they're collapsing
  • 00:21:57
    so lungs would be another tissue that
  • 00:21:59
    you want to allow for them to stretch
  • 00:22:01
    but not separate from one another
  • 00:22:02
    whenever they're actually expanding
  • 00:22:04
    so the lungs
  • 00:22:06
    or any part of your respiratory tract
  • 00:22:07
    really
  • 00:22:09
    also
  • 00:22:11
    your urogenital system which part of
  • 00:22:13
    these would actually be the bigger one
  • 00:22:14
    though
  • 00:22:15
    your bladder right your bladder has to
  • 00:22:17
    be able to stretch and accommodate urine
  • 00:22:19
    so your urinary tract would be a very
  • 00:22:21
    important one so whenever your your
  • 00:22:22
    bladder is getting filled up with all
  • 00:22:24
    that urine and you're like oh baby i
  • 00:22:26
    gotta go
  • 00:22:27
    these cells help to be able to prevent
  • 00:22:28
    those these uh adherence junctions
  • 00:22:30
    prevent these cells from wanting to
  • 00:22:32
    separate from one another they allow for
  • 00:22:33
    more of that stretch
  • 00:22:34
    and again shearing type of abrasive
  • 00:22:36
    forces all right so not just these areas
  • 00:22:38
    but also think about blood vessels blood
  • 00:22:40
    vessels have to be able to stretch right
  • 00:22:43
    particularly it have to undergo what's
  • 00:22:44
    called vasodilation
  • 00:22:46
    so they have to be able to expand but
  • 00:22:48
    they also have to be able to constrict
  • 00:22:50
    so because of that they're going to
  • 00:22:52
    undergo particular you know stretching
  • 00:22:54
    shearing abrasive forces also blood flow
  • 00:22:57
    is hitting against these so there's also
  • 00:22:59
    that type of force there so we want to
  • 00:23:00
    be able to have nice junctions there to
  • 00:23:02
    allow for again the vasodilation aspect
  • 00:23:05
    which prevents the cells from separating
  • 00:23:07
    during that process but also if blood is
  • 00:23:09
    flowing through here and hitting against
  • 00:23:11
    these vessels with high pressure they
  • 00:23:13
    have to be able to accommodate that high
  • 00:23:14
    shearing forces all right what's another
  • 00:23:16
    type of tissue that undergoes a lot of
  • 00:23:17
    you know abrasive and kind of like
  • 00:23:19
    shearing forces the skin right
  • 00:23:21
    yeah so the skins are definitely a big
  • 00:23:23
    one that one's going to take on a lot of
  • 00:23:25
    stretching abrasive types of forces a
  • 00:23:27
    lot of like anything that's really going
  • 00:23:28
    to be involving a lot of excessive
  • 00:23:30
    rubbing against the skin so that would
  • 00:23:32
    be a big thing to think about as well so
  • 00:23:34
    we got git respiratory tract urinary
  • 00:23:36
    tract blood vessels and skin this is a
  • 00:23:39
    big big one though don't forget that one
  • 00:23:41
    and that's one of the things that really
  • 00:23:42
    differentiates tight junctions from the
  • 00:23:43
    adherence junctions as well
  • 00:23:45
    now here's what's really cool clinical
  • 00:23:47
    significance wise you know uh these
  • 00:23:49
    adherence junctions especially those eek
  • 00:23:51
    adherents
  • 00:23:53
    you know whenever people develop cancer
  • 00:23:55
    unfortunately
  • 00:23:57
    cancer
  • 00:23:58
    certain types of genes
  • 00:24:00
    may be
  • 00:24:02
    mutated i guess is the best way of
  • 00:24:04
    saying it and whenever these genes are
  • 00:24:06
    mutated it can alter the structure of
  • 00:24:08
    some of these proteins and what it can
  • 00:24:11
    do is it can alter the structure of
  • 00:24:13
    those cadherin proteins
  • 00:24:15
    and what can happen is if those cadherin
  • 00:24:17
    proteins aren't actually present are the
  • 00:24:19
    cells going to be able to stick with one
  • 00:24:21
    another very well
  • 00:24:22
    no
  • 00:24:23
    and so what happens is these cadherin
  • 00:24:25
    proteins maybe become mutated in a
  • 00:24:27
    particular way where they aren't
  • 00:24:28
    allowing for these cells to stick with
  • 00:24:29
    one another think about why that could
  • 00:24:31
    be a problem let's say that you have
  • 00:24:32
    somebody who develops a cancer right and
  • 00:24:35
    these cells are basically kind of glob
  • 00:24:37
    together you have this mass now
  • 00:24:40
    and
  • 00:24:41
    it undergoes a particular mutation
  • 00:24:43
    and that mutation allows for maybe a
  • 00:24:46
    clump of these cells to separate off
  • 00:24:48
    from one another so let's say that these
  • 00:24:50
    cells just kind of clumped off and
  • 00:24:52
    separate because these actual proteins
  • 00:24:54
    got mutated
  • 00:24:56
    now i can have a clump
  • 00:24:59
    of these cells that can spread from this
  • 00:25:01
    primary location to a secondary location
  • 00:25:04
    of some other portion of the body
  • 00:25:06
    what does that call whenever you have a
  • 00:25:08
    solitary cancer where some of the cancer
  • 00:25:10
    cells can break off and spread to other
  • 00:25:13
    areas of the body this is called
  • 00:25:14
    metastasis
  • 00:25:16
    and so having that process there
  • 00:25:20
    can be due to
  • 00:25:22
    mutations that involve these catherine
  • 00:25:24
    proteins so you see why that's actually
  • 00:25:26
    somewhat significant to think about okay
  • 00:25:29
    now let's talk about desmosomes all
  • 00:25:30
    right so let's talk about desmosomes the
  • 00:25:32
    desmosomes are actually a really cool i
  • 00:25:34
    want you to compare these similar to the
  • 00:25:36
    adherence junctions so they're really
  • 00:25:38
    good for shearing forces again a lot of
  • 00:25:40
    you know pretty much keeping cells
  • 00:25:41
    tightly together
  • 00:25:43
    a lot of abrasive forces they provide
  • 00:25:44
    resistance to that you know again
  • 00:25:46
    shearing and abrasive forces but they're
  • 00:25:49
    stronger than the adherence junctions so
  • 00:25:51
    when you're comparing you have tight
  • 00:25:52
    junctions adherence junctions and
  • 00:25:55
    desmosomes the strength actually of the
  • 00:25:58
    adhesion between the cells is stronger
  • 00:26:00
    as you're going in tight junctions to
  • 00:26:02
    adherence junctions to desmosomes okay
  • 00:26:05
    now what are the proteins that make up
  • 00:26:07
    the desmosome structure when you're
  • 00:26:09
    looking at it again you have these
  • 00:26:10
    proteins they're called cadherins
  • 00:26:13
    so cadherins again these are the
  • 00:26:15
    components of these proteins the red
  • 00:26:17
    ones that are from the cell membrane
  • 00:26:20
    they span outwards into the
  • 00:26:22
    extracellular space so these cadherins
  • 00:26:25
    here
  • 00:26:26
    they're really cool and there's these
  • 00:26:27
    proteins that kind of like connect
  • 00:26:29
    together almost like a zipper really and
  • 00:26:31
    they're really interesting there's two
  • 00:26:32
    types here
  • 00:26:33
    one is called desmoglian
  • 00:26:38
    and the other one is called desmocolon
  • 00:26:43
    so you have desmoglian and desmocolon
  • 00:26:46
    these are two types of cadherins that
  • 00:26:49
    are interlocking with one another in the
  • 00:26:51
    extracellular space now remember what i
  • 00:26:53
    told you
  • 00:26:55
    cad hearings
  • 00:26:56
    what does that mean they're calcium
  • 00:26:58
    dependent proteins so what are you gonna
  • 00:27:00
    have interlocking
  • 00:27:02
    these proteins together you're gonna
  • 00:27:04
    have calcium out here interlocking these
  • 00:27:06
    proteins together it's a very important
  • 00:27:08
    thing so from the extracellular side
  • 00:27:11
    spanning through the cell membrane into
  • 00:27:13
    the extracellular space you have
  • 00:27:14
    cadherins called desmoglian and
  • 00:27:16
    desmocolin and their calcium dependent
  • 00:27:18
    connection
  • 00:27:20
    then you have this big fat plaque
  • 00:27:23
    that actually is going to be anchoring
  • 00:27:24
    these down to the cytosolic part of the
  • 00:27:26
    cell membrane and this is called desmo
  • 00:27:31
    plaquen
  • 00:27:33
    so this is pretty much what's called the
  • 00:27:34
    plaque protein and the main component of
  • 00:27:36
    that is called the desmoplaquen
  • 00:27:39
    okay so this is kind of anchoring the
  • 00:27:41
    actual desmoglean and desmocolon to that
  • 00:27:44
    structure which is going to be again
  • 00:27:45
    more towards the actual in part like the
  • 00:27:47
    cytosolic membrane of that component
  • 00:27:50
    right so you have the cytosolic
  • 00:27:51
    component of the cell membrane that's
  • 00:27:52
    where the desmoplacken is primarily
  • 00:27:54
    anchored and then coming from that out
  • 00:27:57
    into the extracellular space is the
  • 00:27:58
    desmoclean and desmocolon proteins which
  • 00:28:01
    are calcium dependent connection
  • 00:28:03
    okay the next part which is actually
  • 00:28:06
    going to be on the inner side here which
  • 00:28:07
    really helps to hold these cells tightly
  • 00:28:09
    together this purple component here is
  • 00:28:12
    called your intermediate
  • 00:28:14
    intermediate filaments
  • 00:28:17
    and the main component here that's
  • 00:28:20
    really really important is called
  • 00:28:22
    keratin
  • 00:28:24
    so it's keratin that's the main
  • 00:28:25
    intermediate filament
  • 00:28:26
    so
  • 00:28:28
    if i were to ask you again
  • 00:28:30
    the components of the desmosomes from
  • 00:28:32
    the extracellular space you have the
  • 00:28:34
    cadherins desmoglia and desmocol which
  • 00:28:36
    are calcium dependent then on the inner
  • 00:28:39
    cytosolic component of the cell membrane
  • 00:28:40
    of cell one cell two is the plaque
  • 00:28:43
    protein which is mainly desmoplacan and
  • 00:28:45
    then all the way in the cytosol spanning
  • 00:28:47
    into it is the intermediate filaments
  • 00:28:49
    which is primarily keratin
  • 00:28:52
    now we already said a little bit here is
  • 00:28:54
    that these particular desmosomes are
  • 00:28:57
    really good for
  • 00:28:58
    high
  • 00:29:00
    tensile
  • 00:29:02
    stress and stretch right so anything
  • 00:29:04
    that's going to be involving a lot of
  • 00:29:05
    stretch
  • 00:29:06
    anything for a lot of your abrasive
  • 00:29:10
    anything with high abrasive and kind of
  • 00:29:13
    shearing forces is what these things are
  • 00:29:15
    really good at so any abrasive
  • 00:29:18
    shearing forces
  • 00:29:20
    these are extremely extremely good at
  • 00:29:23
    okay
  • 00:29:24
    now
  • 00:29:25
    there's
  • 00:29:26
    two particular types of tissues that i
  • 00:29:27
    want you to remember okay there's a lot
  • 00:29:30
    of them but there's two particular types
  • 00:29:32
    that i really don't want you guys to
  • 00:29:33
    forget
  • 00:29:34
    desmosomes are highly populated within
  • 00:29:37
    your cardiac tissue
  • 00:29:39
    so they're highly populated within the
  • 00:29:41
    cardiac tissue
  • 00:29:42
    and there is a special name for these
  • 00:29:45
    desmosomes that are located in the
  • 00:29:47
    cardiac tissue
  • 00:29:48
    and we'll talk about them
  • 00:29:50
    when you have these cardiac myocytes and
  • 00:29:52
    they're connecting from one another
  • 00:29:54
    we you know heart tissue has to be able
  • 00:29:56
    to stretch accommodate blood coming into
  • 00:29:58
    it
  • 00:29:59
    so what you want is you don't want those
  • 00:30:01
    cardiac myocytes to separate from one
  • 00:30:02
    another so they have to be able to
  • 00:30:04
    accommodate a decent amount of stretch
  • 00:30:06
    so what happens is there is a very
  • 00:30:07
    specific name
  • 00:30:10
    for this thing
  • 00:30:11
    and when we have these they're called
  • 00:30:14
    inter
  • 00:30:16
    collated
  • 00:30:19
    disks
  • 00:30:20
    and basically what these things are is
  • 00:30:22
    there are two components there's the
  • 00:30:24
    desmosomes which is what we're talking
  • 00:30:26
    about now and there's one more thing and
  • 00:30:29
    that is called
  • 00:30:31
    gap junctions and we're going to talk
  • 00:30:32
    about that in a little bit
  • 00:30:34
    but these are the two components that
  • 00:30:36
    make them up in the cardiac tissue and
  • 00:30:39
    again very very high yield don't forget
  • 00:30:40
    this intercalated discs
  • 00:30:43
    so we have cardiac tissue the other one
  • 00:30:45
    is the skin very very important
  • 00:30:47
    especially for the clinical significance
  • 00:30:49
    so i don't want you guys that it's also
  • 00:30:50
    know that it's important for your skin
  • 00:30:52
    tissue especially the epidermis so it
  • 00:30:54
    helps to connect the epidermal cells to
  • 00:30:56
    one another
  • 00:30:57
    why is this important well you know
  • 00:30:59
    there's a disease
  • 00:31:01
    it's a very interesting one it's called
  • 00:31:02
    pemphigus vulgaris you're like what
  • 00:31:05
    pemphigus
  • 00:31:07
    vulgaris
  • 00:31:08
    this is an autoimmune disease
  • 00:31:11
    and
  • 00:31:12
    what happens is your actual immune
  • 00:31:13
    system cells your plasma cells they make
  • 00:31:15
    auto antibodies
  • 00:31:17
    against their own tissues but guess what
  • 00:31:19
    those proteins are that it's attacking
  • 00:31:21
    these antibodies love to attack the
  • 00:31:23
    desmosomes specifically the desmoglian
  • 00:31:28
    and when you actually separate the
  • 00:31:30
    desmoglin when you destroy that then
  • 00:31:32
    these two cells aren't able to connect
  • 00:31:34
    well with one another
  • 00:31:35
    and they start separating and when the
  • 00:31:38
    epidermal cells start separating from
  • 00:31:40
    one another guess what you get
  • 00:31:42
    you get a nasty blistering ulcerative
  • 00:31:44
    type of disease and that's what this
  • 00:31:47
    disease is it's an autoimmune kind of
  • 00:31:49
    skin condition it's a blistering disease
  • 00:31:51
    that's due to the destruction of the
  • 00:31:54
    desmoglin proteins which is basically
  • 00:31:57
    the desmosomes and these can cause nasty
  • 00:32:00
    blisters
  • 00:32:02
    and ulcers
  • 00:32:04
    and one of the biggest things that
  • 00:32:05
    differentiate from the other one we're
  • 00:32:06
    going to talk about is this usually
  • 00:32:08
    involves the oral mucosa whereas the
  • 00:32:10
    other one does not involve the oral
  • 00:32:11
    mucosa
  • 00:32:13
    okay that's the desmosomes now let's
  • 00:32:15
    talk about hemidesmosomes all right
  • 00:32:17
    let's talk about the next type of cell
  • 00:32:18
    junction now this one's actually kind of
  • 00:32:19
    a tricky one because it's not
  • 00:32:20
    technically a cell to cell junction it's
  • 00:32:22
    actually a cell to extracellular matrix
  • 00:32:25
    junction or cell to basal lamina
  • 00:32:27
    junction but that's actually nice
  • 00:32:29
    because it's an easy one to remember
  • 00:32:30
    because it's not a cell true cell to
  • 00:32:32
    cell junction
  • 00:32:33
    so what are the components of the
  • 00:32:35
    hemidesmosomes all right there's a
  • 00:32:37
    couple different proteins so remember
  • 00:32:40
    this is not a cell to sell so let's call
  • 00:32:42
    let's let's actually label this this is
  • 00:32:44
    cell right we can sell one doesn't
  • 00:32:46
    really matter but it's a cell and then
  • 00:32:48
    this blue component here is what's
  • 00:32:49
    called the basal
  • 00:32:51
    lamina and there's a bunch of different
  • 00:32:53
    proteins of the basal lamina right if
  • 00:32:55
    you were to list some of them you'll
  • 00:32:56
    have things like fibronectin
  • 00:32:59
    i'll list a couple of them fibronectin
  • 00:33:01
    is a good one
  • 00:33:02
    can't go wrong with laminin
  • 00:33:05
    and another one that's always a big one
  • 00:33:08
    is collagen so these are some of the
  • 00:33:10
    proteins that are involved in the
  • 00:33:12
    extracellular matrix of the basal lamina
  • 00:33:14
    right
  • 00:33:16
    this is the connection the
  • 00:33:17
    hemidesmondosome is the connection to
  • 00:33:20
    the basal lamina made up of these
  • 00:33:21
    different types of proteins
  • 00:33:23
    to the actual cell membrane okay
  • 00:33:26
    now what are the components of it all
  • 00:33:29
    right so
  • 00:33:30
    the basal lamina i'm just having these
  • 00:33:32
    blue things the proteins like the
  • 00:33:33
    fibronectin the lamina and the collagen
  • 00:33:35
    it's coming up and connecting to this
  • 00:33:36
    purple component that is connected to
  • 00:33:38
    this cell what is this purple component
  • 00:33:41
    here that's really the big thing and
  • 00:33:43
    this purple component here is called
  • 00:33:45
    integrins
  • 00:33:46
    they're called integrins
  • 00:33:48
    okay that's really the biggest thing
  • 00:33:50
    that you guys need to remember out of
  • 00:33:51
    the hemi now is desmond is that the
  • 00:33:53
    integrins are the protein that spans
  • 00:33:57
    through the entire cell membrane of this
  • 00:33:59
    cell and
  • 00:34:00
    connects the cell here to the
  • 00:34:03
    extracellular matrix
  • 00:34:05
    which is the basal lamina consisting of
  • 00:34:07
    fibronectin laminin collagen all of
  • 00:34:10
    these different types of extracellular
  • 00:34:12
    proteins
  • 00:34:13
    what's the proteins
  • 00:34:15
    on the inner cytosolic side of the cell
  • 00:34:18
    membrane that is helping to anchor that
  • 00:34:20
    actual transmembrane protein or the
  • 00:34:22
    integrins down
  • 00:34:24
    this orange proteins are basically the
  • 00:34:26
    same thing as the desmosomes they're
  • 00:34:29
    intermediate
  • 00:34:32
    filaments and this could include
  • 00:34:36
    keratin
  • 00:34:38
    okay so this would include keratin
  • 00:34:41
    that is the basic thing of this
  • 00:34:43
    structure so when we're talking about
  • 00:34:45
    the components of the hemidesmosomes the
  • 00:34:48
    basal lamina which has fibronectin
  • 00:34:50
    lamina and collagen it's connected to
  • 00:34:52
    the integrins which are the protein that
  • 00:34:54
    is actually spanning through the cell
  • 00:34:56
    membrane coming out and connecting to
  • 00:34:58
    the basal lamina and on the inner
  • 00:35:00
    cytosolic side of that cell membrane
  • 00:35:03
    there's the intermediate filaments are
  • 00:35:04
    keratin proteins okay
  • 00:35:07
    what is the different
  • 00:35:10
    basic functions really it's super simple
  • 00:35:13
    because when we talk about these
  • 00:35:14
    hemidesmosomes they're basically helping
  • 00:35:17
    to form
  • 00:35:19
    what's called your basement membrane
  • 00:35:23
    okay it's basically helping to form the
  • 00:35:25
    basement membrane which is just this
  • 00:35:27
    connection of the basal lamina to the
  • 00:35:30
    epithelial cells of different tissues
  • 00:35:32
    that's all it is it maintains that
  • 00:35:35
    connection between the basal lamina and
  • 00:35:37
    the epithelial tissue above it that
  • 00:35:39
    forms the basement membrane that's it
  • 00:35:41
    nothing crazy so
  • 00:35:43
    could you imagine there's a nasty
  • 00:35:45
    disease because really the big places
  • 00:35:48
    that i really want you guys to think
  • 00:35:49
    about this is the skin it's the easiest
  • 00:35:51
    one that makes the most clinical
  • 00:35:52
    relevance so the skin is a big one right
  • 00:35:56
    but any other type of epithelial tissue
  • 00:35:58
    your epithelial tissue the respiratory
  • 00:36:00
    tract epithelial tissue of the gi tract
  • 00:36:01
    epithelial tissue the urogenital tract
  • 00:36:03
    any of those epithelial tissues are
  • 00:36:04
    going to have this i think the skin is
  • 00:36:06
    the easiest one to remember though
  • 00:36:08
    but again remember it's any of the
  • 00:36:09
    epithelial tissues that are lining your
  • 00:36:11
    gi tract respiratory tract and
  • 00:36:12
    neurogenital tract
  • 00:36:14
    with the skin there's a very interesting
  • 00:36:17
    part process here so you know here this
  • 00:36:19
    is the epithelial tissue we call that
  • 00:36:20
    like the stratum basale
  • 00:36:23
    and then that anchors it down to the
  • 00:36:24
    dermis below it right well the anchoring
  • 00:36:27
    connection here if i were to really draw
  • 00:36:28
    it in this kind of like bluish color
  • 00:36:30
    right here this is really where
  • 00:36:33
    your basal lamina is
  • 00:36:35
    so
  • 00:36:36
    what if i had a disease
  • 00:36:38
    where my body has these plasma cells and
  • 00:36:41
    they make these auto antibodies that are
  • 00:36:44
    directed against the proteins the
  • 00:36:46
    entegrins
  • 00:36:48
    that connect the basal lamina to the
  • 00:36:50
    epithelial cells and my antibodies go
  • 00:36:53
    and destroy that connection so what
  • 00:36:55
    would the antibodies do they would
  • 00:36:57
    destroy this connection right here i
  • 00:36:59
    would no longer have integrins anchoring
  • 00:37:01
    the cells to the base membrane and these
  • 00:37:03
    cells would separate so imagine me
  • 00:37:05
    forming a separation between those two
  • 00:37:07
    that's going to form blisters and nasty
  • 00:37:10
    ulcers okay what is that disease called
  • 00:37:13
    it's called bolus
  • 00:37:16
    pemphigoid
  • 00:37:20
    bolus pemphigus so these are basically
  • 00:37:22
    what's called sub
  • 00:37:24
    epidermal
  • 00:37:26
    blisters
  • 00:37:27
    that can actually ulcerate whenever you
  • 00:37:29
    kind of rub them they call it the
  • 00:37:30
    positive nikolsky sign we'll talk about
  • 00:37:33
    it more with derm but these usually
  • 00:37:35
    spare the oral mucosa and they involve
  • 00:37:38
    like the axilla they involve like the
  • 00:37:39
    anal genital area and the different
  • 00:37:42
    inguinal areas and sometimes even the
  • 00:37:44
    trunk as well
  • 00:37:45
    but
  • 00:37:46
    this is the clinical significance is
  • 00:37:47
    that these anchor the actual epithelial
  • 00:37:50
    cells to the basement or to the basal
  • 00:37:51
    lamina forming the basement membrane if
  • 00:37:53
    you have an auto antibodies that are
  • 00:37:55
    destroying that it can separate them
  • 00:37:56
    from these sub-epidermal blisters and
  • 00:37:58
    the condition is called bolus pemphigoid
  • 00:38:01
    we finished talking about the
  • 00:38:02
    hemidesmosomes let's hit it home with
  • 00:38:04
    the gap junctions all right instead of
  • 00:38:05
    the last cell junction that we got to
  • 00:38:07
    talk about here is gap junctions these
  • 00:38:09
    are really cool junctions now the
  • 00:38:11
    biggest thing to remember is that these
  • 00:38:13
    aren't really for
  • 00:38:14
    blocking the movement they're not really
  • 00:38:15
    a diffusion barrier like tight junctions
  • 00:38:17
    they're not really designed to be able
  • 00:38:19
    to resist kind of abrasive and shearing
  • 00:38:21
    forces like the adherence junctions and
  • 00:38:23
    like the desmosomes and they're not
  • 00:38:25
    really anything that's connecting
  • 00:38:27
    another cell to a connective tissue
  • 00:38:29
    these are primarily allowing for cell to
  • 00:38:31
    cell communication which is so cool now
  • 00:38:33
    what are the different components in the
  • 00:38:34
    structures and proteins involved here so
  • 00:38:37
    this whole thing here is called a gap
  • 00:38:38
    junction but a gap junction is actually
  • 00:38:41
    made up of two particular types of
  • 00:38:43
    proteins so when we take a gap junction
  • 00:38:46
    it's actually made up of what's called
  • 00:38:48
    conexons
  • 00:38:51
    connexons and there's two of them
  • 00:38:53
    basically so two connexons make up a gap
  • 00:38:57
    junction so imagine here this whole
  • 00:38:59
    thing here
  • 00:39:01
    this whole component so here's cell one
  • 00:39:04
    and here's cell two if you look right
  • 00:39:06
    here this right here
  • 00:39:08
    is one connexon
  • 00:39:11
    so this is one connexon and then right
  • 00:39:14
    here to this component right here this
  • 00:39:16
    is a another connexon
  • 00:39:19
    these two together are what make up a
  • 00:39:23
    gap
  • 00:39:24
    junction
  • 00:39:25
    now what's really interesting about this
  • 00:39:29
    is that when you actually zoom in on a
  • 00:39:30
    connexon
  • 00:39:32
    a connexon just one of these connexons
  • 00:39:35
    is made up of six this is so annoying
  • 00:39:37
    right two three four five six connexins
  • 00:39:43
    so when we talk about what a connexin is
  • 00:39:46
    so here we have what's called a connexin
  • 00:39:50
    it's made up of what's called connects
  • 00:39:54
    ends and how many six of them so let's
  • 00:39:57
    kind of recap this
  • 00:39:58
    a gap junction is connexons two of them
  • 00:40:03
    and a connexon
  • 00:40:05
    is actually what six connexins together
  • 00:40:08
    that make this big protein
  • 00:40:10
    so if you want to think about how many
  • 00:40:12
    total connections would make up a gap
  • 00:40:14
    junction 12 right because you need one
  • 00:40:16
    connexon another connexon and each one
  • 00:40:18
    of them is six
  • 00:40:20
    so what is the whole purpose to know out
  • 00:40:23
    of this
  • 00:40:24
    well these gap junctions which are made
  • 00:40:26
    up of two connexons and one connexon is
  • 00:40:28
    made of six connexins
  • 00:40:30
    is allowing for cell
  • 00:40:33
    to cell communication
  • 00:40:35
    and that is what's so cool about these
  • 00:40:38
    so if you have for example you have a
  • 00:40:41
    cation like sodium
  • 00:40:42
    or calcium these ions can move from this
  • 00:40:46
    cell to the next cell
  • 00:40:48
    and allow for that ion
  • 00:40:50
    transfer and that can be important in
  • 00:40:52
    certain types of cells that are
  • 00:40:53
    excitable so what kind of cells would
  • 00:40:55
    this be really really important in where
  • 00:40:58
    it's going to be cells where i want them
  • 00:40:59
    to be really excitable right and i want
  • 00:41:01
    them to be able to propagate those
  • 00:41:03
    electrical potentials onto other cells
  • 00:41:05
    nearby
  • 00:41:06
    so that would be a big deal in cardiac
  • 00:41:08
    tissue
  • 00:41:09
    in smooth muscle tissue or even in
  • 00:41:11
    certain types of neurons those are
  • 00:41:13
    excitable cells and we need that
  • 00:41:15
    propagation of electrical activity which
  • 00:41:17
    can be made via these gap junctions or
  • 00:41:20
    cell to cell communications so tissues
  • 00:41:22
    where this can be important in
  • 00:41:24
    is going to be your cardiac tissue
  • 00:41:28
    lots of gap junctions there but again
  • 00:41:30
    what do we call those because remember
  • 00:41:32
    cardiac tissue actually has what's
  • 00:41:33
    called intercollated discs which are
  • 00:41:36
    desmosomes and gap junctions
  • 00:41:39
    the other tissue would be your smooth
  • 00:41:41
    muscle tissue
  • 00:41:44
    so you know smooth muscle tissue
  • 00:41:45
    obviously a good example of this is your
  • 00:41:47
    gastrointestinal tract but you also have
  • 00:41:49
    smooth muscle within the respiratory
  • 00:41:51
    tract
  • 00:41:53
    and you also have smooth muscle within
  • 00:41:54
    the euro genital tract
  • 00:41:57
    so any type of smooth muscle even in
  • 00:41:59
    your blood vessels you actually have
  • 00:42:00
    again smooth muscle
  • 00:42:02
    so again all of these would be
  • 00:42:03
    particular is cardiac muscle smooth
  • 00:42:05
    muscle what else
  • 00:42:06
    neurons
  • 00:42:07
    certain types of neurons is also going
  • 00:42:09
    to be a big one so some specific types
  • 00:42:12
    of neurons actually do communicate via
  • 00:42:16
    gap junctions now
  • 00:42:19
    not only does it allow for ions to move
  • 00:42:22
    from cell to cell but it can also allow
  • 00:42:24
    for certain types of proteins or second
  • 00:42:26
    messenger molecules to move from cell to
  • 00:42:28
    cell you notice uh there's other things
  • 00:42:30
    you know it's called cyclic amp you guys
  • 00:42:33
    have heard that right cyclic amp it
  • 00:42:35
    activates things like protein kinase a
  • 00:42:37
    there's another molecule called ip3
  • 00:42:41
    all of these different types of
  • 00:42:42
    molecules these are like cell signaling
  • 00:42:44
    molecules right and basically if they're
  • 00:42:46
    let's say that you have some type of
  • 00:42:48
    stimulus let's say here's some type of
  • 00:42:49
    molecule
  • 00:42:50
    and it acts on a receptor on this cell
  • 00:42:53
    so here's a receptor on this cell
  • 00:42:56
    when this molecule stimulates this it
  • 00:42:58
    can activate these particular molecules
  • 00:43:00
    exciting this cell
  • 00:43:02
    well maybe this cell would want to let
  • 00:43:04
    the other cell know and so not only can
  • 00:43:07
    ions move from cell to cell but we can
  • 00:43:09
    also have certain types of
  • 00:43:11
    signaling molecules like cyclic amp ip3
  • 00:43:13
    other types of cytokines
  • 00:43:15
    which can alert the cells nearby
  • 00:43:18
    why would that be important let's say
  • 00:43:20
    for example
  • 00:43:22
    let's say you had a cell here and let's
  • 00:43:23
    say here's a
  • 00:43:24
    pathogen here's a pathogen
  • 00:43:27
    and this actual cell gets infected by
  • 00:43:29
    this pathogen alright so now this cell
  • 00:43:32
    is infected
  • 00:43:33
    what this cell could do
  • 00:43:35
    is it could do a couple things it could
  • 00:43:37
    tell the cell nearby hey go ahead and
  • 00:43:39
    make some specific anti-microbial
  • 00:43:41
    proteins against this pathogen and it
  • 00:43:44
    very well could do that
  • 00:43:46
    but it also could say to the nearby cell
  • 00:43:47
    hey man there's a virus nearby there's a
  • 00:43:49
    pathogen nearby you just need to go
  • 00:43:51
    ahead and kill yourself
  • 00:43:53
    and it may actually trigger that cell to
  • 00:43:55
    undergo a programmed cell death to
  • 00:43:57
    prevent it from being infected by that
  • 00:43:59
    pathogen
  • 00:44:00
    and so what it can do is it can signal
  • 00:44:02
    certain types of molecules nearby
  • 00:44:05
    maybe certain types of cytokines and
  • 00:44:07
    tell them hey
  • 00:44:08
    time to trigger
  • 00:44:10
    what's called
  • 00:44:12
    apoptosis
  • 00:44:15
    which is that programmed cell death
  • 00:44:17
    process to be able to protect that cell
  • 00:44:20
    and say hey we don't want this cell to
  • 00:44:21
    have another reservoir for this virus to
  • 00:44:24
    continue to keep populating and making
  • 00:44:25
    more and more viruses just go ahead and
  • 00:44:27
    die so that we can prevent that actual
  • 00:44:29
    virus from being able to have cells as a
  • 00:44:31
    reservoir to continue to keep making
  • 00:44:33
    viruses
  • 00:44:34
    and that may be a process that occurs
  • 00:44:36
    and that can happen not only
  • 00:44:38
    by certain types of molecules being
  • 00:44:40
    released extracellularly
  • 00:44:42
    things like interferons and letting
  • 00:44:44
    these cells know but it can happen via
  • 00:44:46
    these gap junctions communicating with
  • 00:44:48
    the nearby cells saying hey some stuff's
  • 00:44:50
    going on go ahead and prepare yourself
  • 00:44:51
    for that
  • 00:44:52
    and so not only is the function of gap
  • 00:44:54
    junctions allowing for ions to move from
  • 00:44:56
    cell to cell allowing for electrical
  • 00:44:57
    communication
  • 00:44:59
    but also it's important for being able
  • 00:45:01
    to allow for cell to cell communication
  • 00:45:02
    to trigger apoptosis to trigger maybe
  • 00:45:04
    certain cellular adaptive processes to
  • 00:45:07
    undergo hypertrophy atrophy maybe
  • 00:45:10
    whatever it may be but allows for that
  • 00:45:11
    cell to cell communication and it's a
  • 00:45:13
    very cool protective response and that
  • 00:45:15
    my friends finishes our lecture on cell
  • 00:45:18
    junctions i hope it made sense i hope
  • 00:45:19
    that you guys enjoyed it and as always
  • 00:45:21
    ninja nerds until next time
  • 00:45:27
    [Music]
  • 00:45:43
    you
الوسوم
  • jonctions cellulaires
  • barrière de diffusion
  • cadhérines
  • desmosomes
  • communication cellulaire
  • hémidesmosomes
  • implications cliniques
  • pemphigus
  • métastase
  • connexines