Mucosa-associated Lymphoid Tissue (MALT) (Nursing)

00:01 Now let's talk about a very diffuse type of immune tissue called Mucosa-associated Lymphoid Tissue, or MALT for short.

00:11 Now, mucosa is this epithelial lining for things that are basically continuous with the outside world, things that are either taken in by mouth or breathed in and therefore need an extra layer of immune defense.

00:26 We'll start with the tonsils.

00:29 Now, when you hear about the tonsils, you're probably thinking about this type of tonsil called the Palatine tonsil.

00:36 The Palatine tonsil here sitting just below the soft palate, and just behind the back of the teeth.

00:44 That's the typical area when people think of tonsils and they think of tonsillitis.

00:48 But there are other tonsils as well.

00:51 For example, a pharyngeal tonsil, more superiorly just behind the nasal cavity and something called the nasal pharynx.

01:00 There's also small tunable tonsils in this same nasal pharynx area.

01:06 And that has to do with the area of the Eustachian tube which when we talked about the ear is a little tube that connects to the middle ear cavity.

01:16 There are also little tonsils on the tongue, hence the name lingual tonsil because lingual is another term for the tongue.

01:25 And so collectively, these tonsils and collections of lymphoid tissue, whether they palatine or nasal pharyngeal, tubal or lingual sort of form a ring around this initial orifice into the body, and serve as sort of a line of defense before getting too far deep into the body.

01:44 And it's called a Waldeyer's Ring of tonsillar tissue.

01:51 Now, that said, as we get further and further down into the GI tract, there's still going to be the potential for a lot of, you know, potentially infectious things that have been ingested, that we don't necessarily want to be absorbed into the bloodstream.

02:08 And so the rest of the GI tract has other sorts of MALT as well.

02:12 And especially by the time we get to the ileum, we have some really prominent collections that we call Payer's Patches.

02:20 Now, they're scattered throughout the small intestine, but more common in the ileum.

02:25 And at a certain point, they can be so prominent that via endoscope, you might even be able to see little bumps with the naked eye to indicate where Payer's patches are going to be.

02:36 As we move into the large intestine, we have that tiny little thing coming off the cecum that we called the Appendix.

02:44 And the real existence of the appendix is a bit of a debate and some people think there really is no reason for it to exist.

02:52 Others think it's a little potential reservoir of intestinal flora to reseed the intestine after a diarrheal illness.

03:00 And then histologically there's a lot of MALT, so a lot of people think it's, you know, essentially therefore, immune defense.

03:07 And so if you were to look at a cross section of the wall of the intestine, it's really dominated by very prominent patches of lymphoid tissue.

03:18 And so these are all lymphoid follicles in the wall of the appendix.

03:23 And so whether or not the appendix truly does serve a function, at least microscopically, it is a major component of the mucosa-associated lymphoid tissue system.