Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.
Muscles of the Face
Did you know that it takes more muscles to frown than it does to smile? Maybe that's why laughing is so easy! Or that your tongue is actually a muscle? And that the tongue of a blue whale is the size of an elephant? And that, all in all, your face has about 43 muscles in it? All of these muscles are used for things like:
- facial expressions
Of all these muscles, the largest group is associated with the mouth. They are the ones that allow you to open and close your mouth, move your lips and the corners of your mouth and all the movements needed to do things like whistle, smile, talk and eat. Some of the major muscles used in chewing are the buccinator and masseter muscles. These muscles help move food from the front of the mouth back to the throat. The masseter is the strongest jaw muscle - it helps move the jaw bone up and down as you chew. Think of it like this: the masseter is massive, and massive things are strong.
But they don't work alone. The movement of chewing is also aided by smaller muscles called the temporalis and pterygoid muscles. They help move your bottom jaw back and forth and from side to side. If you put your hand on the side of your cheek, then move your jaw like you are grinding your teeth, you can feel the temporalis muscles. And, both temporalis and teeth start with a 'T,' so that might make it easier to remember.
Now, if you move your jaw from left to right, you can feel the pterygoid muscles. They are located behind your teeth and underneath some of the more superficial muscles of your face. If you're a dinosaur fan, you know that pterodactyls have large jaws. And the pterygoid kind of sounds like something a pterodactyl might have to help it move those jaws back and forth.
Muscles of the Neck
Moving below the many muscles of the face and head, you have the muscles of the neck. At the front, many of the outer muscles span the length from your jawbone down to your sternum and clavicle bone. These help the muscles of the face move your jaw.
Moving around to the side and back of the neck, the outer muscles originate at the base of the skull or the vertebrae of the neck and insert down at the scapula. These muscles help support and move your head and neck. You know how when babies are first born they can't hold their head up? It's kind of a little floppy. Well, that's because they haven't developed strength in these muscles yet.
Some of them, like the sternocleidomastoid, are located on both sides of the neck. This pair of muscles flexes the neck, bends the head towards the shoulders and turns your face from side to side. That's a lot of functions for one set of muscles! Others, like the levator scapula, work with the muscles of the back to move the scapula, aiding in shoulder movements and helping you sit up straight, or maintain good posture.
If you were to cut away the outer muscles of the neck, underneath you would see more muscles. These inner muscles control your larynx (or voicebox) and help move food through your pharynx into the esophagus. Without them, you would have trouble both eating and talking.
Muscles of the Back
The back contains numerous axial muscles that run up and down the spine. Together, all these muscles can extend, flex and rotate the vertebral column. In between the longer muscles are smaller ones that help stabilize the vertebrae. Injury to these muscles can result in pressure on the nerves exiting the spinal column, resulting in pain and difficulty moving.
These are covered by the more superficial appendicular muscles of the back, such as the trapezius and the latissimus dorsi. They are considered appendicular because, even though they have origins on the vertebrae, their insertion points are on the appendicular skeleton.
Let's start up at the top. Right below the neck we have the rhomboid muscles. They originate on the cervical and thoracic vertebrae, and insert on the back of the scapula, making it an appendicular muscle. And, just as the name suggests, these muscles are kind of shaped like a rhombus, a stretched-out diamond shape.
Now, take a moment to sit up straight. Part of that movement includes moving your shoulders back toward your spine. This movement of the scapula is the function of the rhomboid muscles. They, along with the serratus muscles on the other side and the levator scapula muscle up top, adduct the scapula, moving it backward toward the spine. You may remember from previous lessons that adduction moves a part towards the body, while abduction moves it away.
And that big large diamond shaped muscle in the middle of the upper back? Well, that is the trapezius. If you have seen our lesson on the shoulder muscles, you may recall that the trapezius, a trapezoid-shaped muscle, helps stabilize and move the shoulder blade.
Moving down to the mid and lower back, we come across this large muscle; that's the latissimus dorsi. The term 'dorsi' can be used to remind you that it is located on the dorsal side, or back, of the body. Its origin points are along the thoracic and lumbar vertebrae, and it inserts along the humerus. Even though this muscle covers most of the back, its main function is extension and rotation of the shoulder. It also adducts the shoulder, pulling it back toward the spine.
So, as you may have already picked up, the back is made up of both axial and appendicular muscles. Which group a muscle belongs to depends on the insertion point and the function of the muscle. If the muscle inserts on and moves the vertebral column, it is an axial muscle, but if it inserts on the appendicular skeleton, it is an appendicular muscle.
All of the muscles of your face are axial muscles because they originate and insert on bones of the head. These muscles are important for actions like seeing, facial expressions, talking and eating. The main muscles involved in eating and moving your mouth are those that move your jaw bone. These include the buccinator, masseter, temporalis and pterygoid muscles.
Below the muscles of your face are neck muscles that help support and move your head. These include the sternocleidomastoid muscles, which flex your neck, move your head from shoulder to shoulder and turn your face from side to side.
Moving around to the back, we have axial muscles of the spinal column. These muscles are attached to the vertebrae and run up and down the spinal column, helping to flex, extend and support the vertebrae.
On top of the spinal muscles are appendicular muscles of the back that move parts of the appendicular skeleton. The rhomboid, serratus and levator scapula muscles adduct the scapula, moving it backward toward the spine. In the middle of your back is the trapezius, which moves and stabilizes the shoulder. Below these are the latissimus dorsi muscles. These large muscles of the back insert on the humerus and extend, rotate and adduct the shoulder.
And remember, these are just some of the main muscles of your face, neck and back, and, unlike your arms and legs, which are all appendicular muscles, the muscles of the back include both axial and appendicular muscles.
As a result of viewing this video lesson, you could be able to:
- Reference the muscles of the face and explain their use
- Recognize the part of the face that includes the largest group of muscles
- Name the muscles of the neck and discuss how they work
- Recognize the muscles of the back and assess their functions
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