The mechanism of coiling of the human intra-epidermal eccrine sweat duct (acrosyringium) was investigated by trtiated thymidine autoradiography, planimetry, three-dimensional reconstruction, and observation of migrating cells labeled with tritiated thymidine or india ink.
Significantly lower proliferation of cells in the acrosyringium as compared to adjacent epidermis was found to be compensated by a high labeling index in the upper segment of the dermal eccrine sweat duct. Ductal cells were observed migrating into the acrosyringium, leading to a surplus of keratinizing cells. This probably induces coiling of the duct. Increased epidermal cell proliferation is incompatible with the formation of a spiraled duct.
Christophers E, Plewig G. Formation of the Acrosyringium. Arch Dermatol. 1973;107(3):378-382. doi:10.1001/archderm.1973.01620180032009