Electron microscope study of the Grandry and Herbst corpuscles in the palatine mucosa, gingival mucosa and beak skin of the duck.

Grandry and Herbst corpuscles of the palatine mucosa, gingival mucosa and beak skin were studied with the electron microscope. Typical Grandry corpuscles are surrounded by thick bundles of collagen fibers and composed of a terminal axon sandwiched between Grandry cells. Occasionally, two or three nerve endings are found within one corpuscle. The Grandry cell contains numerous electron-dense granules similar to those of a Merkel cell. The cell extends protrusions at the poles and the opposing faces. Desmosome-like attachments are noted between interdigitated protrusions, and between the axon and Grandry cell. Herbst corpuscles are composed of an outer capsule, inner core and central nerve ending. The outer capsule consists of 15 to 20 concentric lamellae, while the inner core possesses 60 to 70 sheets of cytoplasmic extensions. Under the scanning electron microscope, the corpuscles appeared as an elongated oval form surrounded by dense fibrous connective tissue, and each lamella of the outer capsule was composed of a dense network of thick and thin fibrils. These were seen under the transmission electron microscope as thick fibrils about 50 nm in diameter and peripheral thin fibrils about 10 nm in diameter. In some portions, a periodic increase of cytoplasmic density about 20 nm in width located in neighboring sheets was noted. The terminal axons of both corpuscles contain numerous neurofilaments, slender mitochondria, neurotubules, smooth endoplasmic reticulum and vesicles. Both corpuscles are limited by several flat cells which are arranged in parallel and probably correspond to the perineural cells of the peripheral nerve. Tight junctions were observed between these cells.