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Representation Check

Biopratiq Anatomical Series  ·  Plate 4 of 6

Fitzpatrick IV

5 of every 12 photons complete the round trip. The rest are absorbed in the epidermis on the way in, or on the way back out.

Fitzpatrick is a phototype scale describing how skin responds to ultraviolet light, in this case rarely burns, tans easily. It is not an ethnic or racial classification, and this plate describes light and tissue rather than any person.

Schematic A teaching schematic, not a measurement. The photon counts illustrate a double pass absorption model with illustrative melanin volume fractions. The anatomy and the mechanism are real and well established; the numbers are there to make it legible.
Anatomical plate: light through the epidermis at Fitzpatrick IV A hand drawn cross section of the epidermis and dermis showing the stratum corneum, granular layer, spinous layer with melanosome caps above each nucleus, basal layer with dendritic melanocytes, and the dermis with collagen and fibroblasts. Light enters, crosses the epidermis, reflects off a lesion in the dermis and crosses back out to a camera. As melanin rises, fewer photons complete the round trip. lightgoes in cameragets what is left stratum corneum dead flattened cells granular layer spinous layer melanin caps sit over each nucleus, shielding it basal layer melanocytes live here dermis collagen and fibroblasts the thing you want to see a lesion, a rash, a change melanocyte one cell feeds many keratinocytes above it 5 of every 12 photons complete the round trip. Two things about melanin Everyone has roughly the same number of melanocytes. What differs between skin tones is not how many pigment cells you have, but how much pigment they make, and how it is packaged. Melanin is not a colour. It is a parasol. Cells park it over the nucleus, on the side facing the light, to shield the DNA. If you photograph a skin concern for a clinician 01 Even indirect light, never flash. 02 Put something in frame for scale. 03 Take one wide and one close. 04 Note the date. Fitzpatrick is a phototype scale describing how skin responds to ultraviolet light. It is not an ethnic or racial classification. Fitzpatrick IV · Plate 4 of 6 · Biopratiq Anatomical Series 1 September 2026 biopratiq.com Schematic. A teaching figure, not a measurement. Melanocyte density: Szabó G, Br Med J, 1954. Packaging: Thong H-Y et al., Br J Dermatol, 2003;149(3):498. Supranuclear caps and DNA shielding: Kobayashi N et al., J Invest Dermatol, 1998;110(5):806.

The Representation Check

How often does the literature report on skin like yours?

This plate is one of six. The Check asks a single question, reports on a published literature rather than on you, and hands back the plate for the band you pick. No account, and no address before the result.

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