This is a tutorial on the hyoid bone and the extrinsic muscles of the tongue. The hyoid bone is this u-shaped bone here which lies between the larynx and the mandible. It’s an important bone because loads of muscles attach to it and it connects the floor of the oral cavity to the pharynx and the larynx below it. You can see all these muscles attaching to this little bone here. I’ll just switch over to an isolated view of the hyoid bone so you can get a better look at it.
There’s three parts to the hyoid bone. You’ve got the body, which is this anterior part and then you’ve got the greater and lesser horn. The greater horn extends posteriorly. It’s this big bit here. The lesser horn is this little bit here. You’ve got the body, the lesser horn and the greater horn of the hyoid bone.
I’m now going to talk about the muscles of the tongue, the extrinsic muscles. The tongue has intrinsic and extrinsic muscles. The intrinsic muscles as the name suggests, they’re muscles within the tongue itself. The extrinsic muscles lie outside the tongue and control the movements of the tongue.
You’ve got four major extrinsic muscles on either side. You’ve got the genioglossus, the hyoglossus, the styloglossus and the palatoglossus. I’ll just dissect away the mandible and deflect some of these facial muscles so we can get a good look at the tongue. I’m getting rid of these suprahyoid muscles as well. The mylohyoid, geniohyoid and all of those. We’re just looking at the tongue muscles now.
Now looking at the muscles of the tongue, you can see through the tongue muscle here. I’m going to start off with this big muscle here, which is called the genioglossus muscle. Remember the prefix genio- refers to the chin. Remember, the geniohyoid muscle connected to the inside surface of the mandible where the chin is to the hyoid bone. This, if I just put the mandible back, you can see it originates on the inside surface of the chin, so that gives it the genio- prefix.
The geniohyoid originates on the inside surface of the mandible on the superior mental tubercles and it inserts along the entire length of the time. You can see the tongue here. Obviously, you know what the tongue is. It inserts along the entire length of the tongue and also onto the body of the hyoid. If we look anteriorly, you can see the insertion of the genioglossus onto the body of the hyoid. This muscle can depress the center of the tongue and it can protrude the tongue.
The next muscle along is this muscle here, this quadrilateral-shaped muscle, the hyoglossus. This muscle originates on the greater horn of the hyoid bone and then it inserts onto the lateral surface of the tongue. What this muscle does is it depresses the tongue. Because it’s got its inferior attachment on the hyoid bone, you can see if it contracts, it will bring the tongue downwards. That’s the hyoglossus muscle.
And then the next muscle along is this one, the styloglossus. As the name suggests, the styloglossus originates on the styloid process. This model is a little bit inaccurate because it’s shown attaching here, but it actually attaches on the styloid process. And then it passes inferiorly and medially to attach along the lateral surface of the tongue. And also, you could see this bit here. The styloglossus also blends with the upper border of the hyoglossus muscle.
And again, looking at the position of the muscle, you can see if it contracts, it will elevate the tongue and it will also (because it lies along the entire lateral surface), it will retract the tongue backwards.
The final muscle of the tongue, extrinsic muscle of the tongue is the palatoglossus muscle. I can’t really show you on this model the palatoglossus muscle because it lies inside the mouth. Basically, you’ve got an aponeurosis between the hard palate and soft palate. It originates from the inferior surface of this palatine aponeurosis and it arches around to attach to the lateral margin of the tongue. What this does, it can depress the palate and it also elevates the back of the tongue. That’s the palatoglossus muscle.
And then you’ve got the other three, which I’ve showed you, the genioglossus, the hyoglossus and the styloglossus. –glossus obviously is Latin or Greek for tongue. And then if you just remember the points from which they originate, it’s easy to remember the name.
Genio-, remember, is the prefix for ‘chin’, so genioglossus originates from the inside of the chin, the mental tubercles and inserts into the tongue.
Hyoglossus, so hyo- referring to the hyoid bone. The hyoglossus originates on the greater horn of the hyoid bone and inserts onto the tongue.
And the styloglossus originates on the styloid process and inserts onto the tongue.
Those are the extrinsic muscles of the tongue.