Muscles of Facial Expression
Directions
- Print this PDF worksheet for a hardcopy guide as you work through this lesson.
- Within the lesson click the red linked headings to bring up the desired starting point within the cadaver for your work.
- Use the provided images on the worksheet to annotate and identify specific anatomical structures.
Welcome back! Begin this investigation with the muscles of the scalp. Identify the following in your specimen:
- frontal belly of occipitofrontalis - This muscle covers the forehead and dome of the skull but it has no attachments directly to any bone. Rather, it originates at a membranous sheet that connects muscle to bone called an aponeurosis. The insertion for the frontalis is the skin of the eyebrows and root of the nose. When contracted, the frontalis raises the eyebrows causing horizontal wrinkles across the forehead. Go ahead and send a contraction message to your frontalis. You will need to use your facial nerve, cranial nerve VII, to get the message there from your brain. Pull your eyebrows up and feel the wrinkles across your forehead.
- galea aponeurotica - This aponeurosis is NOT muscular tissue. This explains why you can't move much around on the top of your head.
- occipital belly of occipitofrontalis - Rotate your specimen 180° to the posterior perspective. The origin of this muscle is the occipital bone and its insertion is the galea aponeurotica. The occipitalis pulls the scalp posteriorly and fixes, or holds, the origin of the frontal belly.
The frontalis is one of three structures that comprise the epicranius. The epicranius is frequently referred to as a muscle but the frontal and occipital bellies of the occipitofrontalis are the muscular portions. The galea aponeurotica is the third part.
Locate each of the following in your specimen:
- orbicularis oculi - This thin, flat sphincter muscle (circular) enables you to squint, blink, and draw the eyebrows downward.
- zygomaticus muscles (major & minor) - The origin of these muscles is the zygomatic bone (hence the name zygomaticus) and insertion is the skin and muscle at the corner of the mouth. The muscles raise the lateral corners of the mouth upward. Smile if you're having a good time; good use of the zygomaticus.
- levator labii superioris - This name translates to "raise lip above or over". Its origin is the zygomatic bone and infraorbital margin of the maxilla. Its insertion is the skin and muscle of the upper lip. You use the levator labii superioris to open your lips, and raise and furrow your upper lip. Show your front teeth like your disgusted and say, "yuuuuk." That's your levator labii superioris.
- orbicularis oris - This translates to "around the mouth." This is a very complicated muscle with fibers running in many directions but most run circularly. Its indirect origin is the maxilla and mandible with fibers blending with other facial muscles fibers associated with the lips. The insertion is into muscle and skin at the angles of the mouth. The orbicularis oris closes and purses, and protrudes the lips. Exercise this muscle by giving someone a kiss, but do not confuse kinetic internalization of new learning with an undue interruption of your studies! :-)
- risorius - When you tense your lips by drawing the corner laterally, you are exercising your risorius. Risorius translates to "laughter." The origin of the risorius is the lateral fascia associated with the masseter muscle (you'll look at it soon). The insertion is the skin at the corner of the mouth.
- corrugator supercilli - This name translates to "wrinkle the eyebrow." Its origin is the arch of the frontal bone and its insertion is the skin of the eyebrow. This little muscle draws your eyebrows together wrinkling the skin of your forehead vertically. This is exercised with the eye and brow posture that accompanies a frown.
- buccinator - First, dissect away the left and right depressor anguli oris and the orbicularis oris. Now, locate the left and right buccinators. Buccinator means "cheek or trumpeter." The origin is the molar region of the maxilla and mandible. The insertion is the orbicularis oris. The buccinator draws the corner of the mouth laterally and compresses the cheek (as when whistling and sucking). To gain a better perspective, rotate your specimen to 45°.
Locate the following in your specimen:
- depressor labii inferioris - The name means "depresses below the lip." Its origin is the body of the mandible and its insertion is the skin and muscle of the lower lip. Its function is to draw the lower lip downward. Make a pouty face; that's your mentalis (the next muscle you'll find) and depressor labii inferioris working together.
- mentalis - Dissect away the right and left depressor labii inferioris to gain a better view of the mentalis. (Remember, you do this clicking once to select the muscle then clicking again to remove it.) "Ment" is Latin for "chin." Realize that this is superficial to your previous dissection level. The origin of the mentalis is the mandible below the incisors. The insertion is the skin of the chin. The mentalis protrudes the lower lip and wrinkles the chin.
- depressor anguli oris - We'll continue laterally to the depressor anguli oris muscle. This name translates to "depresses the corner of the mouth." It's origin is also the mandible and its insertion is the skin and muscle at the angles of the mouth below the zygomaticus insertion. The depressor anguli oris is antagonistic (opposite action) of the zygomaticus. The depressor anguli oris pulls the corners of the mouth downward and laterally. Imagine you just got some really bad news and grimace. That's it!
- platysma (pla-TEEZ-ma) - (I just like the sound of it!) Platysma means "broad and flat." Although not specifically a head muscle, the platysma plays a role in facial expression. It helps depress the mandible and pull the lower lip back and down. Men exercise this muscle when shaving their neck. Not trying to be sexist, women would exercise this muscle when shaving their necks, too. :-0 The origin is the fascia of the chest over the pectorals and deltoids (you'll learn these shortly). The insertion is the lower margin of the mandible, as well as the skin and muscle at the corner of the mouth.
Go get a snack. You'll soon learn muscles used for chewing and tongue movement so why not do a little applied learning!
Self-test Labeling Exercises