Rough draft.This research track is under review with Dr. Atit's lab. Content and sequence may still change.
The Baby Mateo Case
Developmental domainPrinciples of Biomedical Science (PBS)Lesson 6 of 20Your seat: Embryologist
How the Palate Begins: Secondary Palatal Shelf Outgrowth
Discovery question
Where does the back of the come from, and what makes it grow?
💡 A must actively grow to the right size on schedule, driven by signals that tell cells to divide, or the two shelves may never have enough to meet.
The plan
Prerequisite check
Before this page, you should know
- The two medial nasal processes merge into the , which becomes the , the four upper incisors, and the primary .
- The upper lip closes at about human weeks 4 to 6 when each fuses with the medial nasal block beside it.
If not, review
Today's new idea is only
A must actively grow to the right size on schedule, driven by signals that tell cells to divide, or the two shelves may never have enough to meet.
Learn first
What you will learn
Goal: Explain that the secondary begins as two shelves that grow downward from the maxillary processes, and that their growth depends on cell driven by signals in the .
Know by the end
- The roof of the mouth behind the lip is the secondary ; it begins as two palatal shelves that bud from the maxillary processes at about human week 6.
- The shelves first grow vertically (downward), one on each side of the tongue, and are made mostly of neural-crest-derived .
- A shelf reaches full size by (cells dividing), and this growth is driven by signals in the , not automatic.
- If a shelf grows too little, the two shelves may never have enough to meet, and a can result; this is one possibility, not a verdict for Mateo.
Learn first
Model: The timeline strip and a growth experiment in mice
Pull the craniofacial timeline. The primary (front triangle) forms at human weeks 5 to 6 (mouse about E11.5). At about week 6 (mouse about E11.5 to E12.5) the secondary palatal shelves grow out vertically beside the tongue: two shelves bud from the maxillary processes and point downward, like two curtains hanging on each side of the tongue. Later (week 8, Lesson 7) they will elevate to .
Scientists studied a mouse missing the gene Msx1. In normal mice the front of the palatal shelves grows by adding many new cells. In the Msx1 mutant the front of the shelf had too few dividing cells, the shelf stayed too small, and the ended up . When the team added back a single growth signal (Bmp4) in the shelf, normal growth and a closed palate were rescued. So a is not just there; it is a block of that must actively grow to the right size, and growth depends on signals telling cells to divide.
Do the work
Explore (work the model before reading on)
- Where on the do the secondary palatal shelves grow out from?
- Which direction do the shelves first grow: up, down, or sideways?
- In the Msx1 mutant, what two things went wrong in the shelf (think cell number and shelf size)?
- Why would too few dividing cells lead to a shelf that is too small? Connect cell division to size.
- The rescue added a growth signal and fixed the shelf. What does that tell you about why the shelf normally reaches full size?
The plan
Guided notes
1
Where the palate begins
Model start: The roof of the mouth behind the lip is the secondary . It begins as two palatal shelves that bud out from the paired maxillary processes at about human week 6.
- At first the shelves grow ____ (vertically / downward), one on each side of the tongue.
- They are made mostly of ____, the loose inner that came from cranial .
2
Growth is driven, not automatic
- A shelf reaches full size by ____ (), which means cells dividing to make more cells.
- This growth is driven by ____ in the ; remove them and the shelf stays too small and the clefts.
3
Keep it on the table, not as a verdict
- A must grow to the right size on ____.
- For Mateo, a growth failure is one ____ to investigate, not yet something we have ruled in or out.
Explore
Reading the Research
What to read
Read the title and the abstract only, not the whole paper. Lan & Jiang 2015, Cellular and Molecular Mechanisms of Palatogenesis (Curr Top Dev Biol)
Why this source matters
This is the published evidence behind today's idea: A must actively grow to the right size on schedule, driven by signals that tell cells to divide, or the two shelves may never have enough to meet.
Words to unlock first
Reading moves
- 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.
Stop point
You do not need the methods or statistics yet. If a sentence is about lab technique or math you have not learned, mark it and skip it.
Your output
Write one claim-evidence sentence: what this source claims, and the one piece of evidence that backs it up.
Where this fits
Tested on (Ohio WebXam)
Genetics of Disease · 072130
PLTW lesson
MI · Developmental domain · Cell division and growth in secondary-palate formation
WebXam domain
Bio-Molecular Technology
Evidence to produce
Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.
Lab / skill
Principles of Biomedical Science (PBS) · Medical Interventions (MI)
Explore
Vetted readings for this lesson
- Lan & Jiang 2015, Cellular and Molecular Mechanisms of Palatogenesis (Curr Top Dev Biol)
- Bush & Jiang 2011, Palatogenesis: morphogenetic and molecular mechanisms of secondary palate development (Development)
- Zhang et al. 2002, Rescue of cleft palate in Msx1-deficient mice by transgenic Bmp4 (Development)
The plan
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.
Check off as you finish
- 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: Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.
- Wrote my Claim, Evidence, and Reasoning exit ticket.
Pick your period and code first.
Check yourself
Exit ticket (Claim, Evidence, Reasoning)
- Claim: The secondary begins as ____ that must ____ to reach full size.
- Evidence: In a mouse missing a growth signal, the shelf had ____ and the was ____.
- Reasoning: This matters for Mateo because a could begin as early as the ____ step, before the shelves ever try to meet.
How this is graded (rubric)
For: Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.
| 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. |
How the model answer scores against this rubric
- CompleteProficient: Nothing is left blank: the model fills every part of "Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.".
- 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.
Explore
Where this leads: careers
Developmental biologist Geneticist Craniofacial researcher
What's next: The begins as two shelves that grow downward beside the tongue. But those shelves point straight down, with the tongue sitting between them. How do two downward shelves end up as one flat roof above the tongue? We chase that next time.