The Muscles That Make a Lip and Palate Work
Which muscles let the lips seal and the soft lift, and why does the direction their fibers run matter?
💡 For these muscles, direction and continuity decide function; a present muscle pointed the wrong way still fails.
Prerequisite check
- The upper lip has a central bordered by philtral columns, with the where colored lip meets skin.
- The roof of the mouth has a bony in front and a movable in back.
What you will learn
Goal: Describe the as a ring that seals the lips and the as a sling that lifts the soft , and explain why fiber direction and continuity matter.
- The is a , a continuous ring of muscle around the mouth that crosses the to seal the lips.
- The is paired; the left and right fibers join in the to form a sling across the soft .
- That sling lifts the soft up and back to seal the , shutting the nose off from the mouth during speech and swallowing.
- A muscle that is interrupted or pointed the wrong way cannot do its job even if the skin looks closed.
Model: The lip ring and the palate sling
The core muscle of the lips is the . Imagine a ring of muscle that circles all the way around the mouth, like a drawstring around the opening of a bag. In a normal lip the fibers run continuously and cross the of the upper lip, so when the muscle tightens it closes and purses the lips evenly. A muscle that closes an opening by squeezing in a ring is a . Because its fibers are continuous across the midline, a baby can seal the lips to hold milk and later to make sounds like p, b, and m.
The most important muscle of the soft is the . There are two of them, one on each side. Each starts up near the base of the skull (close to the Eustachian tube, which drains the ) and sweeps down, forward, and toward the . The key detail: the fibers from the left and right muscles meet in the middle of the soft palate and join, forming a sling (a band running side to side, like a hammock). When this sling contracts it lifts the soft palate up and back to touch the back wall of the throat, sealing the . MRI studies confirm that in a normally formed palate the levator forms exactly this transverse, midline-continuous sling.
Explore (work the model before reading on)
- The is described as a ring. What opening does that ring surround?
- In a normal lip, do the orbicularis fibers stop at the or cross it?
- Do the levator fibers run side to side across the soft , or front to back?
- A closes an opening by squeezing inward. Why must the be continuous across the to seal the lips evenly?
- Predict: if a muscle's fibers ran front to back instead of side to side, could it still lift the up and back to seal the ? Explain.
Guided notes
The lip muscle
- A muscle that closes an opening by squeezing in a ring is a ____.
- To seal the lips evenly, the orbicularis fibers must be continuous across the ____.
The palate muscle
- The left and right fibers join in the middle to form a ____ (sling).
- When the sling contracts, it lifts the soft to seal the ____ (the valve to the back of the throat).
The rule
- The big idea: ____ and ____ decide function (a ring must be unbroken across the ; a sling must run side to side and join in the middle).
Reading the Research
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Vocabulary (the same words your classes use)
Track your progress today
Check these off as you work through the lesson, then submit. This tells Mr. Mendoza how you're doing so he can help the class. It does not replace turning in your producible.
Use the code Mr. Mendoza gave you, not your name. Saved on this device.
- Read the Model and answered the Explore questions.
- Filled in the guided notes in my own words.
- Defined the new vocabulary with an example.
- Built the producible: On a top-down view of the lips and a from-below view of the soft palate, draw with colored arrows the normal fiber direction of the orbicularis oris and the levator veli palatini. For each muscle, write one sentence: what job it does and what would break if it were interrupted.
- Wrote my Claim, Evidence, and Reasoning exit ticket.
Exit ticket (Claim, Evidence, Reasoning)
- Claim: For the lip and the , a muscle's ____ is just as important as the muscle being present.
- Evidence: Give the normal direction and continuity of the and of the .
- Reasoning: Explain why a muscle that is present but pointed the wrong way could still fail to do its job.
| Criterion | Proficient | Developing | Beginning |
|---|---|---|---|
| Complete | Every required part of the artifact is present and filled in. | Most parts are present, but one is missing or left blank. | Several parts are missing. |
| Accurate | The science and data are correct and match the evidence. | Mostly correct, with a small factual slip. | Key science or data is wrong. |
| Scientific reasoning (CER) | States a claim, backs it with specific evidence, and explains the reasoning. | Has a claim and evidence, but the reasoning is thin or missing. | Gives an answer with no evidence or reasoning. |
| Professional communication | Clear, organized, and labeled the way a clinician or scientist would write it. | Readable but disorganized or missing labels. | Hard to follow. |
| Submitted | Turned in the right way (Schoology for routine work) and confirmed. | Turned in, but in the wrong place or unconfirmed. | Not turned in. |
- CompleteProficient: Nothing is left blank: the model fills every part of "On a top-down view of the lips and a from-below view of the soft palate, draw with colored arrows the normal fiber direction of the orbicularis oris and the levator veli palatini. For each muscle, write one sentence: what job it does and what would break if it were interrupted.".
- AccurateProficient: Every number and claim matches the case evidence.
- Scientific reasoning (CER)Proficient: It names a claim, cites the specific evidence, and explains the reasoning, not just the answer.
- Professional communicationProficient: It is organized and labeled like a real chart note.
- SubmittedProficient: It would be turned in on Schoology and confirmed.
Where this leads: careers
What's next: We know the normal muscle plan and the rule that direction and continuity decide function. But we have not yet looked closely at Mateo. So what exactly is interrupted in his lip and , and what happens to these muscles? We chase that next time.