Food for Not

So I was eating cake for lunch today, as per usual, and I noticed something in my neck moved upwards every time I swallowed! To make sure it wasn't just me, I watched other people's throat as they ate (a little creepy but I had to get to the bottom of this anomaly!). And I noticed the same thing, something in their throat moved up when they gulped down their food or took a drink. It was most apparent in males; I saw their entire adam's apple move up, and then back down again!  Since the adam's apple is a quintessential landmark for the larynx, I had a sneaking suspicion that the larynx was involved in this process. And being the larynx fanatic that I am, I had no choice but to delve deeper into how this all worked. Here is what I found:

The pharynx is a common passage way for both food and air, but at a certain point (i.e. at the larynx) their fates diverge. Air passes through the larynx into the trachea, and food slides posteriorly over the larynx (via the epiglottis) and into the esophagus. There are three main "guards" to prevent the aspiration of food into the airway, and they are: the epiglottis, the vestibular folds, and the true vocal folds. 

The epiglottis itself, as mentioned in the jewelry post regarding the laryngeal cartilages, is a piece of leaf shaped elastic cartilage that is amply situated to cover the glottis during swallowing. When we swallow, there are a set of extrinsic muscles attached to the hyoid bone that first move the hyoid up, and then out anteriorly (1). These are known as the "elevator" muscles, some of which include the thyrohyoid, digastric, stylohyoid, and mylohyoid muscles. Since the larynx is inadvertently attached to the hyoid bone via the thyrohyoid membrane, the whole larynx follows the motion of the hyoid bone. During laryngeal elevation, the epiglottis folds posteriorly and down over the glottis, protecting the vocal folds. Once the food has slid past the larynx on the epiglottal "food slide" into the esophagus, a set of "depressor" muscles move the hyoid bone posteriorly and inferiorly back to it's resting position. Some of the muscles involved are the sternothyroid, omohyoid, and sternohyoid muscles. 

Okay so the epiglottis is the first "guard" preventing food aspiration, the second guard involves the vestibular folds (aka the false vocal folds). If you missed our post about the difference between the false and true vocal folds, catch up on this cheeky imposter here. The vestibular folds are adducted (brought closer together) so that food is prevented from getting past to the more delicate vocal folds. And interestingly enough the vocal folds themselves are the third, and last "guard" that prevents food from getting into the trachea. The adductor muscles bring the vocal folds together to seal off the glottis yet again. But all in all, the first and main structure that ensure food bypasses the airway is the epiglottis. The adduction of the vestibular and true vocal folds are only in place as backups. 

As you can see, there are many structures that prevent the aspiration of food into trachea because it's very important to maintain an open airway or we wouldn't be able to breath! And this is the first and main function of the larynx, so remember this! Phonation, though extremely interesting and talked about here, is only a secondary function of the larynx. But even with all these mechanisms in place, food can still enter the trachea sometimes! That's where the cough reflex comes in, which interestingly enough, is turned off when we are unconscious(2)....but that's a post for another time. 

Whew, looking into all of that was tough work. Time for another piece of cake to exercise those extrinsic laryngeal muscles because you know what they say, if you don't use it, you lose it!

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References:

1. McCulloch TM, Jaffe D. Head and neck disorders affecting swallowing. GI Motility online. 2006 May;do:10.1038/gimo36
2. Marieb E, Hoehn K. Human anatomy & physiology. Boston: Pearson;2013. 

Current State of the Glottis

Dear Larry,

I've been a long-time reader of your blog, and I just wanted you to know that I'm thankful for you, and The Larynx and You! It was such a relief to find a larynx sanctuary online, because no one I know gets quite as excited as I do... Anyways, I just wanted to ask if you could impart some more information on the pronunciation component of vocalization. I'm really curious to know your thoughts!

Sincerely,

A pharynx in need is a pharynx indeed

Hi Pharynx! First off, thank you for your kind words. It's getting feedback from readers like you that really make this blog worth it. I know exactly how you feel about not being able to find a larynx appreciation community offline, and I feel so blessed that I was able to come into contact with folks such as yourself with the press of a few buttons! Secondly, I would be glad to go into a little bit more detail regarding the way we articulate words! I went into it very briefly in my post "How to be a Prima Glottis" (which is perhaps what sparked your interest), and hopefully this post will shed more light on how we, as human beings, are able to manipulate the sounds our larynx produces in order to articulate words for language! (Warning: Things may get a little bit linguistics-y, but please bear with me!)

First, I want to talk about the position of the vocal cords in our larynx. (Remember that this is controlled by the intrinsic musculature, and the arytenoid cartilages!) These folds have the ability to be abducted, adducted, or somewhere in between, and this state of the glottis will determine whether the sound produced is "voiced" or "voiceless." An easy way to differentiate between the two is to feel your larynx for vibration when you make a sound. Try this: make a "t" sound and then a "m" sound. As you can tell, there's no vibration when you make the "t" sound (voiceless) and you can feel vibrations when you make the "m" sound (voiced)! Basically, this distinction has to do how close together the vocal cords are. For a voiceless sound, they are abducted, meaning that there airflow won't cause much, if any, vibration. For a voiced sound, the folds are much closer together (although they may not be completely adducted), which means that the air flowing through them will cause vibrations! Consonants can be both voiced and voiceless, while vowels tend to be voiced.

After our larynx produces a sound, the sound has no choice but to travel through the vocal tract where it can be moulded to the individual's needs. As humans, no matter what country or culture you may originate from, we usually morph these vocalizations to form words for communication.

All these different structures in the vocal tract are different places of articulation. This simply means that by changing the orientation of one or more of them, we can change the shape that a sound takes. For example, a "bilabial" is a sound that can be made by bringing the lips together, such as "p," "b," and "m." Another example is an "interdental" sound, which are the sounds that are made by placing your tongue in between your teeth, namely "th." There are a few other classes of sound that have been grouped together for their place of articulation, and I urge you to look them up if you're interested!

And lastly, I thought I'd mention manner of articulation. This is just how the speech organs (mentioned above) interact and position themselves to form different sounds, by manipulating the airstream supplied by the lungs. Three examples are stops, fricatives, and glides. Stops are when airflow is completely stopped in the oral cavity, such is the case for sounds such as "k," and "p." Fricatives are for sounds that aren't completely stopped, but have been restricted somewhat due to a narrowing in the oral cavity. Some examples of fricatives are "s" and "f." Glides are the opposite of stops and fricatives, because they're made when there is no obstruction or restriction in the oral cavity or airway. "Y" and "w" sounds are considered glides. As with places of articulation, there are a lot more categories, but since they're just a Google search away I didn't think it was necessary to list them all here.

And there you have it! My dead Pharynx, I hope you found this little spiel useful in your pursuit of everything larynx related (although most of this was only indirectly related to the larynx). Best of luck, and if you ever want someone to chat with, you know where to find me!

#DOTD Tag: Laryngitis

I’m back with this week's #DOTD (Disease of the Day) post! Laryngitis has been a hot topic amongst our readers lately, so I thought I’d bite the bullet and write about it before there were any more brawls over “which larynx-related disease is the best” in our comments section… Read on, my fellow larynx enthusiasts!

1) What is it?

Laryngitis is simply the inflammation of the larynx, which results in pain or discomfort of the throat. Usually, people who have laryngitis will have a hoarse or croaky voice, or they might even lose their voice completely depending on the severity of the inflammation! Upon examination (possibly via a laryngoscopy), the patient might be seen to have various inflamed structures (such as their vocal cords, or even their arytenoids), or excessive secretion of mucous. (1) 

2) How do you get it?

Most people have had laryngitis at some point in their lives. If you've ever strained your voice (which is pretty easy to do if you're like me at concerts!) to the point where you feel pain in your throat, you've most likely had it! There are lots of other ways of getting laryngitis, however. Bacterial infection, environmental irritants (for example, cigarette smoke) and other health problems such as allergies may result in inflammation. It's really common to see laryngitis when you've caught a cold as well, or as a result of acid reflux which can damage the larynx.

3) What are some symptoms?

There are a variety of symptoms that come with laryngitis, and most of you have probably experienced a lot of them. Like I mentioned before, along with a plain old sore throat, you can have a hoarse voice and even lose your voice completely if it’s severe enough. You'll probably find yourself wanting to cough because of the irritation and itchy feeling in your throat, or constantly be clearing your throat if there's a lot of mucous buildup. (1)

4) How do you treat it?

If your laryngitis is mild, and you know you have it because you were out doing some loud karaoke last night, you can probably make do by just resting your voice and drinking some warm honey tea. Some people suggest gargling with warm salt water to clear out the mucous, or even breathing humidified air to ease the discomfort of an itchy, dry throat. If these don't work, it's recommended that you go see a doctor because they may be able to prescribe steroids to help with the inflammation!

5) Anything else?

There are acute and chronic types of laryngitis, and which one you have depends on the duration of the affliction. Laryngitis due to having a cold, or because you strained your voice one day will probably lead to you having the acute version, but if you smoke or suffer from reflux, your symptoms will most likely be chronic.

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References: 
1. Ulualp SO, Toohill RJ, Hoffmann R, Shaker R. Pharyngeal pH monitoring in patients with posterior laryngitis. Otolaryngol Head Neck Surg. 1999 May; 120(5):672-7.

The Nerve (of some people)!

This post may be a bit boring in comparison to some of the others I’ve written for this blog, but I feel that exploring the innervation of the larynx is an essential component to fully understanding its function. We’ll keep it fairly simple, so don’t worry about getting bogged down in the details!

In terms of innervation, it’s the vagus nerve (cranial nerve X) doing most of the work in the larynx. As you may or may not know, CNX is a mixed nerve, meaning that it has the ability to give motor, sensory and parasympathetic innervation, which is exactly what it does in the larynx! There are two branches that come off of the main nerve which go to innervate our larynges. They are the superior laryngeal nerve, and the recurrent laryngeal nerve. Take a look at the following diagram to see where they enter the larynx:

Let’s talk about the recurrent laryngeal nerve (RLN) first. You can see that it enters the larynx inferiorly, and that it splits off further into two sub-branches: the internal and external branches. The internal branch of the RLN gives the larynx some of its sensory innervation, especially to the vocal cords and the subglottic region. (1) The external branch of the RLN is important for motor innervation. It innervates all of the intrinsic laryngeal muscles (except for the cricothyroid muscle which is innervated by the superior laryngeal nerve) and will be the one sending signals to make the muscles move. (Which is essential to being able to vocalize!) (1)

Next up is the superior laryngeal nerve (SLN), and from both the name and the diagram above, I hope you all have managed to discern that it enters the larynx superiorly. The SLN gives the larynx most of its sensory innervation, especially in the area above the vocal cords. (2) When you’ve been singing and yelling with your friends at the local karaoke bar for hours on end, this is the nerve that will let you know! In the majority of people, the SLN has three branches - superior, middle, and inferior - and these simply go to different areas in the larynx.

That about sums up everything I wanted to share with you guys in regards to the innervation of the larynx. I wanted to keep it short and sweet in the hopes that you wouldn't be bored to tears. Until next time!

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References: 
1. Ardito G, Revelli L, D'Alatri L, Lerro V, Guidi ML, Ardito F. Revisited anatomy of the recurrent laryngeal nerves. Am J Surg. 2004 Feb; 187(2):249-53.
2. Sanders I, Mu L. Anatomy of the human internal superior laryngeal nerve. Anat Rec. 1998 Dec; 252(4):646-56.
3. Marieb E, Hoehn K. Human anatomy & physiology. Boston: Pearson; 2013.

Cartilage Décollage

So a couple weeks back I came across this company called Krikoeides (greek for "ring-shaped") that specializes in making jewelry based off the nine cartilages of the larynx. How nifty is that! I've ordered everything from their catalog, and the pieces should be arriving soon. 

So far I have only received the cricoid ring, and it's actually made out of hyaline cartilage. Hyaline cartilage is the type of cartilage found in the nose, and on the ribs for reference, so it's quite durable. The cricoid, is the only fully circular cartilage of the larynx, so it's quite ingenious of the designers at Krikeoeides to make a ring based off the cricoid. 

The thickness of the ring varies, so it gives the piece some dimensionality which is an A+ in my books. Anteriorly, the ring is shorter and thicker; while posteriorly, the ring is taller and thinner. The ring looks amazing, and it makes a great statement piece that's sure to strike up a very phonetic conversation. 

I can't wait for the other pieces to arrive. The other unpaired cartilages come in single statement pieces, so there is a piece each for the epiglottis and the thyroid cartilage. As for the three paired cartilages (making up the other 6 cartilages of the larynx), they come in earring sets! Krikoeides really thought things through when coming out with this larynx collection. 

The epiglottis is a spoon shaped elastic cartilage, however other people have noted that it looks like a feather, and the main role of the epiglottis is to cover the glottis (opening into the larynx and lower airway) to prevent aspiration during swallowing. The design of the (on the)glottis pendent is striking, since there is enough slack in the chain to enable you to layer other long necklaces with this pendent. The designers took the more feather like approach to give the pendent a more whimsical look, rather than an ice cream scoop. However, I think if the Krikoeides designers were in the kitchen appliance industry, an epiglottis shaped ice cream scoop would have been the way to go. And it could be thermo-sensitive, since the epiglottis has tastebuds on it and the colour change could simulate this interesting tidbit. Anyways, that was a bit on a tangent, so let's get back to the topic of this post. Larynx cartilage based jewelry, and up next we have the last unpaired cartilage, the thyroid!

The thyroid cartilage based bracelet cuff is seriously neat stuff. The bracelet itself is pretty hefty, which makes sense since the thyroid cartilage is one of the main structural components of the larynx, and acts as an attachment point for various membranes. Via the thyrohyoid membrane, the superior aspect of the thyroid cartilage (and inadvertently the larynx) is attached to the inferior portion of the hyoid bone. Also, the thyroid is the attachment point of the larynx to the hyoid bone via the thyrohyoid membrane. Inferiorly, the thyroid cartilage is attached to the superior portion of the cricoid cartilage by the median and lateral cricothyroid ligaments. The cricothyroid muscle also spans this region, and is important in narrowing the space between the cricoid and thyroid cartilages to that the vocal folds can be tensed. My favourite thing about this bracelet is the protuberance on the front that mimics the laryngeal prominence (aka the adam's apple). This bracelet could do some serious damage so don't get on my bad side! 

Moving onto the 3 paired cartilages, we have the arytenoids, corniculates and cuneiforms. The designers decided to make two pairs of earrings based off of these cartilages. The first set utilizes the pyramidal shape of the arytenoid cartilages, and articulating on the apexes of the arytenoids are small horn like prominences to serve as the corniculate cartilages, also known as the cartilages of Santorini. These earrings definitely catch your attention because of the unique shape of the arytenoids, but I somewhat wish Krikeoides designed a pair of earrings showing the cricoarytenoid joint. 

This joint within the larynx is a highly mobile synovial joint, and the arytenoids sit at a 45 degree angle on the cricoid cartilage. Movement is permitted in three planes due to the unique placement of the arytenoids: they can slide medially and laterally, twist along their vertical axis, as well as rotate along the oblique axis in a rocking like motion. All these movements act to change the positioning and tension of the vocal folds, so if they had a pair of earrings like this I'm sure I could spend hours fiddling around with the various positions the cricoarytenoid joint allows. 

As for the pair of earings based off the cuneiform elastic cartilages, also known as the cartilages of Wrisberg. Within the larynx, the cuneiform cartilages can be found the in aryepiglottic folds, so they do not directly articulate with the other two paired cartilages  However, they still move with the arytenoid and corniculates during vocal fold adduction and abduction. These stud like earrings are wedged shaped and fairly elongated, which you don't see in many designs. I'm excited to see how these will fit, I mean will the look better as a helix stud or would they be better situated on my earlobe. Decisions, decisions, decisions... 

Well hopefully this post has entertained you, and has amped you up for this jewelry collection! I seriously can't wait to get the rest of the shipment in, but for now I will admire the cricoid ring that I have and voice my enthusiasm to anyone willing to listen.   ____________________________________________________________________________

References: 
1. Hammer, G, Windisch G, Prodinger P, Anderhuber F, Friedric G. The Cricothyroid Joint - Functional Aspects with Regard to Different Types of Its Structure. Journal of Voice. 2010;24(2):140-145. 
2. Sellars I, Sellars S. Cricoarytenoid joint structure and function. The Journal of Laryngology & Otology. 1983;97(11):1027-1034.  

How to be a Prima Glottis

1. Voice Projection and Power

So you're an amateur singer, and you're pretty good. Unfortunately the people at the back of the theatre can't hear you hit those exquisite verbrattos. So what can you do? Train your diaphragm! The more air you have at the bottom of your lungs, the more air pressure you have to force those vocal cords open to project your voice to infinity...and beyond. Inspiration occurs when the thoracic cavity expands, and the main muscles involved are the external intercostal muscles and the interchondral portions of the inner and innermost intercostal muscles. But if we recruit the diaphragm, forcing it to contract, the chest cavity will further expand since the abdominal viscera is being compressed by the flattened diaphragm. If you only fill the upper portions of your lungs, then there is less pressure available to rush past the vocal cords through the rima glottis. The result will be a breather and quite voice. However, if the entire chest cavity is filled with air, the higher pressure will allow you to project your voice louder and further! Remember, vocalization all starts with the upward flow of air out of the lungs, so you can't speak when you're breathing in!


2. Pitch and Vocal Quality

Okay hot shot, now the entire audience can hear you. But what about the quality of your voice? Like I said, you're pretty good, but you can be so much better if you trained your intrinsic laryngeal muscles, which as the ones responsible for the vocal cord manipulation to give you that vocal range. There are 5 muscles involved, and their main functions are to abduct, adduct, and tense the vocal cords. 

Okay, so first take a deep breath. As you're doing this, the glottis (opening into the larynx) is forced wide open as the posterior cricoarytenoid muscle (PCA) abducts the vocal cords. Now as you begin to hit your first note, you're laryngeal adductor muscles close the glottis by bringing the two vocal folds together. So remember to train your thyroarytenoid (TA), interarytenoid (IA), and later cricoarytenoid (CA) muscles so that the adduction is as efficient as possible! Okay, so the glottis is sealed off, and as you start to expire (releasing the stored air in your lungs) the air pressure beneath the glottis will start to rise. We will call this sub-glottal pressure. Depending on the tension applied to the vocal folds, namely by the actions of the vocals and thyrocricoid muscles, different amounts of sub-glottal pressure will be required to force apart the vocal folds so that the air can escape. 

a) Movement of the posterior cricoarytenoid muscle; b) Movement of the interarytenoid and lateral cricoarytenoid muscles; c) Movement of the thyroarytenoid muscle (medial portion is the vocalis muscle of the vocal fold)   

The tighter the vocal folds are, the greater the sub-glottal pressure needed cause the vocal folds to vibrate. So a higher pitched voice will be produced since the vibrational oscillations are shorter and faster. If we want to  apply some physics terminology, the pitched produced is higher (or of greater frequency) because the oscillating waves on the vocal folds are shorter, and wavelength is inversely proportional to frequency. Likewise, as the vocal folds are relaxed, less sub glottal pressure is required to cause the vocal folds to vbrate. And when they do vibrate, the wavelengths are longer, thus the sound produced is of a lower register. 

Movement of the cricothyroid muscle on the
cricothyroid joint leading to tension of the
vocal folds. 

The process in which the vocal fold vibrates as expired air exits through the glottis is explained by the body-cover theory (1). In this theory, the vibrational motion (wavelengths) starts in the sub-glottal portion of the vocal fold. Here the mucosal portion of the vocal fold oscillates over the stiffer ligamentous portions; or more technically stated the superficial lamina propria oscillates upon the vocal ligament composed of the intermediate and deep lamina propria. If you need a refresher on the composition of the vocal ligament click here. This mucosal wave then propagates medially towards the free edge of the vocal fold where it is carried up onto the supra glottal region as the passage of expired air forces the two vocal folds apart. The mucosal wave now moves laterally, away from the glottal opening.

The sound produced by the vibration of the vocal folds resonates through the pharynx (the portion connecting the larynx to the oral/nasal cavities) and out through the mouth. The pharynx itself, as well as the bony sinuses in the skull act as resonating chambers to amplify the sound waves. 


3. Pronunciation 

Alright, so now you're able to hit those high and low notes with ease. But unfortunately there are lyrics in the song you're going to perform! So how does the bare mechanics of pronunciation work? Well, it all has to do with the shape of your mouth/oral cavity that can be changed through the use of the tongue and lips. If you don't believe me, try speaking while holding your tongues or rolling your lips around your teeth! How difficult was that?

However, this is a very simplified explanation of the pronunciation process. Pronunciation itself involves the complex interplay between the brain and the mechanics of the various muscles involved (besides those mentioned in the mouth and larynx.)

Well, there you have it. You're going to be an astounding vocalist now! So don't be lackadaisical and go get to practicing for your debut! Till next time, cheers! 

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References:
1. Simpson C, Rosen C. Operative techniques in laryngology. Berline: Springer;2008.

Cheeky imposter

In the larynx, there are two sets of vocal folds (1). The first set of vocal folds that you come across as you enter the larynx are known as the vestibular, or false vocal folds. And one may assume these vestibular folds help in the vocalization process, but this is a false pretence! The vestibular folds only aid in protection of the  lower air passage way (1) as well as the true vocal folds found directly underneath where the real magic happens. 

The vocal folds themselves are composed of a vocal ligament and the vocalis muscle (an extension of the thyroartnoid muscle)(2). The vocal ligament itself is composed of two lamina propria layers, intermediate and deep respectively. These two layers are fairly rigid due to the presence of dense elastin and collagen matrixes. 

Coronal section through the free edge of the vocal fold, 

demonstrating the layers micro anatomical structures that 

allow vibration. (2)  

The dense vocal ligament acts as a support for the superficial lamina to vibrate upon. The superficial lamina is highly gelatinous, and is free to oscillate as air is expired through the larynx. If you think about it, this motion is similar to that seen on a water bed, with the superficial lamina propria being the water portion, and the intermediate and deep layers being the floor. 

So there you have it, the imposter and the true set of vocal cords that do all the work to help you speak! And with knowledge of the complex layers of the true vocal cords, you can spot the difference between the true and the false cords with ease. 

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References: 
1. Marieb E, Hoehn K. Human anatomy & physiology. Boston: Pearson; 2013.
2. Simpson C, Rosen C. Operative techniques in laryngology. Berlin: Springer; 2008.