If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

What is chlamydia?

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Raja Narayan.

Want to join the conversation?

Video transcript

- [Voiceover] Chlamydia is the most common sexually transmitted infection in the world. Sexually transmitted infection. And you might recall from our conversation about gonorrhea, chlamydia often co-infects with gonorrhea, or they tend to occur together. Now there are several species of chlamydia that exist, but when we talk about the most common STI that's responsible for the disease chlamydia, we're talking about chlamydia trachomotuis, trachomotuis. And the way it gets this name, trachoma is the term for the eye infection that occurs with chlamydia, as we'll talk about in a minute. Now with any sexually transmitted infection we have to consider the mechanism by which the infection spreads from one person to another. And that process is called transmission, and there are several ways that chlamydia is transmitted from one person to another. Sex is the most common way and that can include oral sex, vaginal sex and anal sex. Childbirth is another important mechanism for transmission, as we'll talk about in a few minutes. And finally one of the unique ways that we can transmit chlamydia that we can't with many other sexually transmitted infections is with direct contact. Now I want to throw a big asterisks over here. Because chlamydia can only live outside of a human host for about a few seconds to a minute. So direct contact means something like scratching an infected organ of the body, say part of the genitalia, and then directly touching another part of the body like the eye. This doesn't count for one person touching another person directly and spreading the infection. That's very rare and unlikely to occur. Direct contact means to spread from a person to another part of that same person's body. And we'll talk about that in the case of conjunctivitis or an eye infection of chlamydia. So now let's move this list off to the side, and focus on my poor friend right here, who's going to have all the different signs and symptoms you can get with chlamydia. Now as I mentioned already, chlamydia is mainly spread through sex. So why don't we start by focusing on the sexual organs right here, which I've drawn out already. And I want to label this side as the female. So right here is the urethra, right here is the entrance to the vagina, the vagina, which leads up here to the cervix, the cervix. And I won't label it here but this is the anus and this leads up to the rectum and the rest of your lower gastrointestinal tract. And on this side we have the male that starts with the penis, the testicle, the prostate, the bladder, the urethra, and I'll label the rest of this in a minute. But let's focus here on the female. Now let's say for instance that this female is infected by a male, and so here's a chlamydia trachomotuis bacterium that's making its way into the vagina. And I'll just label this as our key up here, that's what I'm going to draw chlamydia to look that. And from here the chlamydia will multiply and spread further up the genital tract on it's way to the cervix. And the same thing can occur with the urethra nearby. Perhaps we can have chlamydia spread up this way and into the urethra. And the interesting thing about chlamydia is that it's predominantly an intracellular organism, or an intracellular bacterium, which just means that it likes to live within a cell. Which in this case means, the human host cell or the epithelial cells that line the vagina, or the epithelial cells that line the urethra. Now the symptoms that we have that are associated with chlamydia are due to the white blood cells that come and attack the bacterium. What they do is that they'll notice that there are chlamydia inside of these epithelial cells, and they will target the cells that are infected to cause a process that's called apoptosis, apoptosis; which is the very neat and organized killing of a specifically selected cell. So I'll write here cell death. So it's cell death that is programmed by the white blood cell. Now as I've drawn here, we usually don't have a single chlamydia bacterium that comes to infect the genital tract or the urinary tract. You're going to have many of these guys that are inoculated or spread into the tract. So there's going to be, as a result, a lot of white blood cells that come from the blood stream to the genital or the urinary tract to attack the infected epithelial cells or any chlamydia they can eat up that's outside of the cells at the time. And when all these white blood cells show up from the blood stream and go to the genital or the urinary tract where they're not suppose to usually be, we get this process of inflammation. Inflammation, and that's what causes us the swelling, the burning, and the general pain that's associated with a chlamydia infection. That means that at the urethra when it gets infected, you have urethritis, urethritis. And the burning sensation you have when you pee is called is dysuria, dysuria, which just means uria referring to the urinary tract and dys meaning some complication or something that's out of whack, or has a disorder, dysuria. The same can be said for an infection of the epithelial cells that line the vagina, resulting in vaginitis or if they go further up here to the cervix, you get cervicitis, cervicitis. And just like there's a term for painful urination, there's a term for painful sex or intercourse. And that's called dys, which means disorder again pareunia, dyspareunia. Where pareunia just means the act of intercourse or sex. Now there are a lot of similarities that you can draw here in the case of the male. So say if we have some of the chlamydia bacteria spreading up the urethra, the urethra. That'll cause urethritis. Or if it spreads up here to the prostate, this pink guy over here that's the prostate, you can get prostatitis, prostatitis. Now the one thing I should mention that's different in the case of the female versus the male is that there's an opening from the uterus into the abdominal cavity through the fallopian tubes. And so if the chlamydia spreads so far up through the cervix in to the uterus and out the fallopian tubes, they can actually seed or spread into the abdominal cavity. And this happens as well with gonorrhea and the term we use for this type of infection is called pelvic inflammatory, pelvic inflammatory disease. Pelvic inflammatory disease or PID. And there are several other complications that can occur because of having PID, and we'll talk about that in a separate video. And I've run out of space to show it here but another very telltale sign of a sexually transmitted infection, especially when white blood cells are coming from the blood stream to attack the infected epithelial cells and the bacteria, you're going to have that apoptosis or that cell death that occurs along the way. And so, the dead epithelial cells, the dead white blood cells and even the bacteria will come out of the tip of the penis from the urethra or from the urethra in the female. And what you'll actually see is pus. So you're going to have, what can also be referred to as a creamy, purulent discharge or just pus that represents the dead white blood cells, epithelial cells and bacteria that are being essentially peed away. Now from the genitals, chlamydia can spread into the blood stream to go elsewhere in the body. And there are a couple of very classic places it shows up. One place it can spread from the blood stream, right here is the eye. So I've drawn this gentleman's eye down over here and he's looking downward. And remember, as I mentioned just now, in addition to spreading from the blood stream, chlamydia can also spread from direct contact into the eye. Let's say if there's some pus that's discharged and a person is confused about why that's coming out and they touch it with their finger and then rub their eye, you can directly spread chlamydia into the eye. And it starts by affecting this reddish portion right here, and that's called the conjunctiva, the conjunctiva; which is just a fancy name for the inside of the eyelid. Now if the chlamydia spreads here, what you're going to start seeing are these bumps that occur on the conjunctiva, on the inside of the eyelid. And these bumps will accumulate and start scratching on the eye. And when they scratch on the eye they're going to start causing irritation here as well. And so, the conjunctiva which is infected can be referred to as conjunctivitis. But once you start irritating the white of the eye over here you may actually even spread the infection over the pupil here, to cause what's called an opacity. Which just means this whitening over the pupil that makes it difficult for you to see. And this is what is referred to as trachoma, trachoma; which is the most common cause of blindness in the developing world. Another site that can be affected from the blood stream are your joints. So this knee right here can be infected. So we refer to this specifically as infective arthritis, infective arthritis. I'll write arthritis here a little more in the middle, infective arthritis. Which is exactly what you would imagine the chlamydia spreads from the blood stream into your joint capsule right here. This white layer is bone, here's bone as well. And this grey portion is the articular cartilage, or the cartilage that separates the bones from each other. And in between in the joint capsule or this synovial cavity is this fluid, it's referred to as synovial fluid, that sort of helps the bones move on top of each other smoothly. So remember as chlamydia makes it into any part of the body, not just in the joint, but also the urethra, you're going to have white blood cells that come right after it. And these guys are chasing it with a vengeance. and so you're going to have those telltale signs of inflammation occurring here in the joint as well. And I'm sure you can imagine that having a ton of white blood cells here within the joint makes it very difficult for you to have smooth movement if, in addition to the fluid, you've got these white blood cells and now you've got some chlamydia that's here. You're going to have a lot of pain and difficulty moving. And the term for painful joints is dysarthria, dysarthria; which dys again means some type of disorder and arthria refers to the joint, dysarthria. Now a unique thing about chlamydia is that in addition to infective arthritis, you can also have something that's referred to as reactive arthritis, reactive arthritis. And this is a very distinct beast from infective arthritis, in that reactive arthritis is the result of the antibodies that you make. So I'll just write AB for antibodies. The antibodies that you're suppose to make against the chlamydia; which for some reason in this case will attack both the chlamydia trachomotuis as well as the joint for some reason. So reactive arthritis is the result of antibodies that are suppose to attack the chlamydia, for some reason mistaking proteins in the joint for the same proteins that are on the chlamydia and traveling to the joint to attack it as well. And when antibodies flow into some space, the similar thing happens as what we saw here with infective arthritis. White blood cells will also rush to the site to help the antibodies attack whatever it is they're attacking. And unfortunately in this case, those include proteins that are naturally found in the joint capsule. This is a really unusual phenomenon that occurs and it's sometimes associated with chlamydia. And in fact has its own name or syndrome, this is called Reiter's Syndrome, Reiter's Syndrome. And it can be best remembered by this popular mnemonic, where if you have Reiter's Syndrome, you can't see because you've got trachoma like you do here. You can't pee, because you have urethritis. And then on top of that you can't even climb a tree, because you've got reactive arthritis. Now in addition to Reiter's Syndrome if you have an infected mother, she can spread chlamydia to her newborn child. And have something like this occur, and this is referred to as neonatal chlamydia, neonatal chlamydia. And first off you might notice here the crusting of the eye; which is similar to something we already talked about, this is conjunctivitis. But you can also see pneumonia in an infected newborn. And depending on how much the chlamydia will multiply and spread to the baby in the uterus, you may also have premature labor. So the baby will be delivered earlier than they should be, or even death. Which is why it's important for pregnant women to be checked for chlamydia. Because this disorder can be completely preventable.