Two Shelves Become One Roof: Adhesion, the Medial Edge Epithelium, and the Seam
Take the reading one piece at a time. For each piece: read it once, underline the sentence that says what happens, then look up any word in the list. Tap a word to see its definition.
Piece 1 of 2
Zoom in on the medial (midline-facing) edge of one elevated shelf. From inside out you see mesenchyme in the core (the growing inner tissue), a surface epithelium covering the edge whose midline-facing part is the medial edge epithelium (MEE), and capping the very outside a thin layer of flat protective cells called the periderm. Think of the periderm as a non-stick wrapper that keeps embryonic surfaces from sticking to whatever they brush against.
Piece 2 of 2
Here is the puzzle. For the two shelves to join, their edges must STICK together, but the periderm is a non-stick wrapper whose job is to keep surfaces from sticking. So before the shelves can adhere, the periderm over the MEE must be cleared at exactly the right moment. Just before the shelves touch, the periderm cells over the MEE round up and are shed; then the two bare MEE layers press together and adhere, intercalating into a single shared layer down the midline, the midline epithelial seam (MES). The genes that build a proper periderm (including the IRF6 program) control whether this clearing happens on cue, and if periderm is faulty, surfaces stick in the wrong places or will not adhere where they should, and fusion fails.
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.
Now put it together: In one or two sentences, say what this whole reading is telling you about Mateo. Then go back to the lesson and fill in the guided notes.