A world at your fingertips: sources & model

Slide a texture beneath a finger. See the contact change, compare a moving touch with a steady one, and zoom from skin to a real sensing protein. Discover how touch differs from pain.

What supports the explanation?

What this model assumes

1. The finger and enlarged cutaway are original teaching geometry, not a scan, patient anatomy or a biomechanical contact solver. Layer thicknesses, receptor size and skin indentation are illustrative.
2. Only regular ridge motion has quantitative timing: f = |v| / λ. Playback is slowed fivefold. The ridge counter counts travel in complete ridge intervals from trial start, not neural spikes.
3. Press–hold–release signals are qualitative authored response envelopes. Heights and playback times are not measured firing rates or physiological thresholds.
4. The mouse PIEZO2 model uses PDB 6KG7 assembly 1. Nonprotein carbohydrate atoms and alternate B atom locations are omitted. Its inspection separation is not a molecular motion or a working partial channel.
5. The microscopy is a static, licensed image of human skin. Optical brightness is not electrical activity. The study included ten participants; this lesson does not infer personal receptor density.
6. This lesson introduces nociception and pain; it does not model pain intensity, diagnose sensation, or reproduce all sensory pathways. Independent subject and learner review of the finished lesson is pending.
7. A spatial pattern becomes a temporal pattern: If successive ridges are λ millimeters apart and pass at speed v millimeters per second, one cycle takes T = λ / |v| seconds. Therefore f = |v| / λ cycles per second, or hertz. At 20 mm/s and 4 mm spacing, f = 5 Hz. At 40 mm/s and 8 mm spacing, it is also 5 Hz. The equation counts the external stimulus, not action potentials.
8. Which skin are we looking at?: This is an authored illustration of glabrous, or hairless, fingertip skin. Its outer epidermis includes the stratum corneum. Beneath it is the dermis; deeper tissue includes subcutaneous fat. Meissner corpuscles sit in dermal papillae near the surface. Merkel cell–neurite complexes are associated with the basal epidermis. These structures differ in arrangement and response; our enlarged cutaway shows one Meissner-like corpuscle, not a complete receptor atlas.
9. What did human recordings show?: Johansson and Vallbo’s 1979 study recorded 334 low-threshold mechanoreceptive units in awake humans. Response types and receptive-field properties differed across units and hand regions. Their measurements do not support labeling every touch as one universal sensor or assigning one response rate to everyone.
10. From genes to selective human evidence: Chesler and colleagues studied two people with biallelic loss-of-function PIEZO2 variants in 2016. Their selective sensory and movement findings help establish PIEZO2’s role in humans. A small, unusual genetic study is not a population-wide sensitivity test, and the 3D structure here is separately sourced from mouse PIEZO2.
11. What the three-part structure establishes: Wang and colleagues’ 2019 cryo-electron microscopy study determined a mouse PIEZO2 assembly, deposited as PDB 6KG7. We preserve the three protein chains and their common coordinate frame. The smoothed envelope is a rendering of deposited atom positions; it is not a density map, observed channel opening, or a propeller spinning in skin.
12. Temperature involves different molecular routes: The discovery of heat/capsaicin-sensitive TRPV1 and cold/menthol-sensitive TRPM8 helped identify molecular contributions to temperature sensing. Neither establishes one exact sensation temperature for everyone or makes the channel the sole detector of all hot or cold experiences.

What has been checked

Analytical reference cases, conservation or transition invariants, finite drawing commands, bounded setup parsing, discovery and route integrity are checked automatically. These checks do not establish anatomical fidelity, learner outcomes or browser/device compatibility. Independent subject review, learner trials, comprehensive accessibility review and browser video encoding checks remain pending.

Each source supports the associated claim. Sources do not certify this implementation or its visuals.

About the cover illustration

Original rendering of the lesson’s authored fingertip and periodic ridged surface. It is not a skin scan or calibrated deformation. The real human microscopy and source-derived mouse PIEZO2 assembly have their own credited evidence views.