Anatomy and Physiology Series: Inhalation Anatomy

I've been reading up in my handy-dandy textbook from the previous post to try to figure out just what is the most important stuff to include for students and teachers of singing, as well as anyone making public speeches. However, I have encountered the issue of an abundance of riches: There's so much information that I think it'll be too hard to include it in just one post on inhalation and one post on exhalation as I planned. So, I'm going to split up some of these posts, where I see fit, and do inhalation anatomy as one post and some key inhalation physiology as another post before moving on to exhalation. I feel there is so much contradictory "theory" of breath support in the singing world out there that an effort to explain more scientific detail than what is usually gone over will be worth it...if I pull it off.

Inhalation can be an over-looked issue with some singers out there. I work a lot with inhalation when I get students who need the work. This is due to the ways in which a person can inhale, i.e. the many different coordinations of the musculature of the torso, thorax, and neck, and the biological function of those different coordinations.  We'll get into those functions in the next post, but for now, on to the inhalation musculature!

We have all heard, in one way or another, of the primary muscle of inhalation, the diaphragm.  This is the bowl-shaped muscle that rests under the lungs.  It flattens downward upon contraction (inhalation), and returns to it's resting bowl-shape on exhalation thanks to muscular elasticity.  It is innervated by the phrenic nerve, which originates in the cervical plexus.  It is bilaterally innervated, meaning there is nerve routes to the diaphragm on both sides of the body.  This is mainly a protective measure so that if there's damage on one side, the nerves on the other side will keep it working (a sign that it's a pretty important muscle for the body.)  It is attached to the lungs via pleural lining and the central tendon, which is the big white area on the picture below.  When you're at rest, this is the main muscle controlling inhalation.  (note, this is an inferior view, basically looking up through the abdomen.  The central tendon, however, is on the superior (top) of the diaphragm, so they have it here just to show it.  In fact, the heart is above the central tendon.)

These other muscles of inspiration are considered accessory muscles.  They are considered such because if you're knocked unconscious, this muscles aren't really used for inspiration at rest.  (Physics and elasticity from the last post does the work there.)  So these guys help mostly in what we call "forced inspiration," like what we do when we speak, sing, exercise, etc.  The external intercostals are included in this category (although they do play a role in resting inhalation as well, we could breathe at rest just fine without them...so they're considered accessory as well.)  These guys run between the ribs, are "external" to the internal intercostals (expiration muscles) and do not attach all the way around the ribs, stopping short of the sternum because attaching there would not do any good in elevating the ribcage, which is what they do.  You can see them labeled between the first and second rib show in this picture.  (That large, flat muscle shown here is one of the internal oblique abdominals...we'll get too on expiration.)

The other accessory muscles of inspiration, like the intercostals above, have to do with elevating and expanding the ribcage in some way.  These include the levator costarum, located at the back of the ribs near the spine.  There are 12 pairs of these muscles for each of the 12 ribs.  (They're the little red guys in the image below.)

The serratus posterior superior are paired muscles that originate from the spinous process (part of the vertebrae that sticks out) and inserts into the upper borders of the 2nd through the 5th ribs.  I'm having a heck of a time finding a good image that I trust won't carry some virus or something (been burned by that before!), so I'll just link to an image I like here:  They're the group labeled #1.  

There are other accessory muscles I have deemed less important for the singing/teacher/speaker to know, but I'll list them along with a link if you want to know more:  erector spinae, lateral bundle, and intermediate bundle.  These guys are more involved in spinal and rib cage stabilization than respiration directly.  (The last two in that list are on the first link.)

But, we're not done yet!  If you're not totally asleep by now, (and if you are, I don't blame you, anatomy without good physiology to back it up is pretty darn dry!), I'm gonna add in some of the accessory neck muscles to respiration.  These are primarily the sternocleitomastoid and the scalenes.  (If you've taken a pedagogy class before, you've probably heard of at least one of those, huh?)

The sternocleitomastoid is a strong muscle of the neck.  It originates from the mastoid process (the bump you feel right behind your ear) and has two points of insertion, the sternum and the clavicle (put all three together, and you've got it's name).  If just one side of this muscle is contracted, it results in rotating your neck towards the contracted side.  If both sides are contracted, it results in the sternum and clavicle (and by association the upper rib cage) being elevated.  But I like to think this muscle is the most happy when it's busy rotating your neck instead of aiding in respiration.

The scalenes (anterior, middle, and posterior) is a group of three muscles that, biologically speaking, help to stabilize the head and help out in neck rotation as well.  But, since they also insert into the 1st (for the anterior and middle scalenes) and 2nd (for the posterior) ribs, they can also elevate the upper rib cage.  (In the image below, you can see the anterior and middle scalene under the sternocleitomastoid.  The posterior one is being "hidden" by some muscles that go over it.)

Are we done yet?  (That's what I'm thinking right now, but no, I'm not done yet...I suppose you could be, though, since this is a blog entry after all.)  There are muscles of the arm and shoulder that aid in forced inhalation as well.  I think I'm just going to link to some of them, cause some are known pretty well in pop culture thanks to some hollywood hotties out there.  Pectoralis major and minor both elevate the sternum, which ends up increasing the rib cage in transverse (or side-ways) motion.  Serratus anterior help to elevate ribs 1-9.  Levator scapulae, which is actually what's hiding the posterior scalene in the image above, is a neck stabilizer, but it can elevate the rib cage as well.  

I'm going to include these next guys here because I feel they are key players in proper breathing posture for operatic singing (but, keeping this entry strictly dry, boring, and all about the anatomy).  Rhomboideus major and minor are often included in inspiration since their main function is to stabilize the shoulder girdle.  The trapezius is also often included.  This guy is a pretty big, strong muscle.  It supports arm movements, moves (and can stabilize) the scapulae (i.e. shoulder blade), elongates the neck, and helps to control head movement.  (You might have found yourself working this one out in the gym, along with pectoralis major.)  

So what do you have to look forward to with inhalation physiology?  The difference between diaphragmatic breathing and clavicular breathing, biological functions of both of these, and which of these muscles we just went over are our friends and which ones are our enemies when it comes to singing...duh, duh, duuuuuuuhhhh!!  (That's my poor attempt at suspenseful-sting music there...yeah, it's time to go.)




*Citation: Seikel, J. A., King, D. W., & Drumright, D. G. (2010). Anatomy and physiology for speech, language, and hearing. Clifton Park, NY: Delmar.