Schematic overview of equine hoof lamellar tissue anatomy.

Left panel: cut away view of the midsagittal section of an equine foot outlining position of lamellar tissue (red) relative to hoof wall (grey) and distal phalanx (DP), middle phalanx, and distal sesamoid bones (blue). The transverse section plane used for tissue collection is shown in yellow. Center panel: a portion of the transverse section plane diagrammed schematically. The interdigitating primary epidermal lamellae (PEL) and primary dermal lamellae (PDL) are highlighted. Positions relative to the skeletal axis are denoted as axial (closest to DP), middle, and abaxial (farthest from DP and closest to the hoof wall). Right panel: higher magnification illustration of lamellar tissue organization. Colors are overlaid on a tissue section stained to highlight cell membranes and extracellular matrix (rhodamine-tagged wheat germ agglutinin, see Methods). Darker blue overlays mark basal epidermal cells, yellow overlays mark suprabasal epidermal cells, light blue overlay highlights the keratinized axis (KA) of each PEL. The PEL consists of combined secondary epidermal lamellae (SEL) and KA. Dermal tissues are shown in red overlays, with light red highlighting PDL and darker red marking the secondary dermal lamellae (SDL).