When the Outside World Reaches the Embryo
Can the outside world change how the face forms, and if so, how strongly?
💡 Environmental exposures such as low , smoking, and valproate raise or lower the probability that succeeds during the window; they are risk-modifiers, not single causes.
Prerequisite check
- The lip closes (medial nasal plus maxillary ) during human weeks 4 to 6.
- The secondary grows, elevates, and fuses during human weeks 6 to 12, with complete by about week 12.
What you will learn
Goal: Explain how environmental exposures ( status, smoking, valproate) change the probability that lip and succeeds, and rank them as risk-modifiers rather than single causes.
- A teratogen is an environmental agent that can disturb normal development, but only if it acts during the structure's critical window.
- Low maternal is studied as a modifiable ; the protective size for clefts is debated and weaker than for neural-tube defects.
- Maternal smoking is a repeatedly reported association for orofacial clefts, with the mechanism still being worked out.
- Most exposures raise or lower the probability of a rather than guaranteeing one, which is why we say not cause.
Model: Three exposures, three kinds of evidence
What the developmental and epidemiology literature actually says about three common prenatal exposures (SYNTHESIS.md Section 4.4; PMID:28550290).
Low maternal (a B-vitamin that supplies methyl groups): periconceptional folic acid is studied as a modifiable factor that may lower risk; biologically plausible and recommended, but the protective size for clefts is debated and less settled than for neural-tube defects.
Maternal smoking (tobacco smoke in pregnancy): repeatedly associated with higher risk across many studies; an established statistical association whose exact mechanism is still being worked out.
Valproate (an anti-seizure or mood medication): listed among anti-epileptic-drug exposures studied as and birth-defect risk factors; a recognized teratogen class where dose and timing matter.
Timing matters too: an exposure at week 6 to 9 overlaps the growing, elevating, fusing ; an exposure at week 20 arrives long after the palate has fused (PMID:26589921).
Explore (work the model before reading on)
- Which exposure has the strongest, most settled link to clefting, and which is most debated?
- Between an exposure at week 6 to 9 and one at week 20, which one could actually change ?
- adds something the needs, while smoking and valproate add something harmful. Why might both missing a helper and adding a harm raise risk?
- Why do scientists use the word or associated with instead of causes for smoking and clefts?
- Mateo has a complete left lip and and no other birth defects. If a teratogen were the whole story, what else might you expect to see in his body, and what does its absence suggest?
Guided notes
What a teratogen is
- supplies methyl groups used to build and regulate DNA; low maternal folate is studied as a ____ (modifiable) , with a debated protective size for clefts.
- Maternal smoking is a repeatedly reported ____ (association) for orofacial clefts.
Risk, not destiny
- Valproate belongs to a drug class studied as a teratogenic ____ (risk) factor for birth defects including clefts.
- Most exposures ____ (raise or lower) the probability of a rather than guaranteeing one, which is why we say , not cause.
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.
Vetted readings for this lesson
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: Write a one-paragraph teratology note for Mateo's chart. State: (1) which of the three exposures, if present, could plausibly have acted during his fusion window, (2) why you would still NOT call any single exposure the cause, and (3) one prevention message for a future pregnancy. Flag every uncertainty honestly, the way the sources do.
- Wrote my Claim, Evidence, and Reasoning exit ticket.
Exit ticket (Claim, Evidence, Reasoning)
- Claim: The outside world (can / cannot) change whether Mateo's lip and fuse.
- Evidence: One exposure and what the literature says about its strength.
- Reasoning: Why timing within the critical window decides whether an exposure matters, and why we say not cause.
| 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 "Write a one-paragraph teratology note for Mateo's chart. State: (1) which of the three exposures, if present, could plausibly have acted during his fusion window, (2) why you would still NOT call any single exposure the cause, and (3) one prevention message for a future pregnancy. Flag every uncertainty honestly, the way the sources do.".
- 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: Yes, the environment can tip the odds during the window. But here is the puzzle: the same exposure can reach two embryos with the same DNA and only one of them clefts. How can identical DNA give different results?