Scanning Electron Microscopic Study on Collagen Fibrils in the Mink Dermis during the Hair Cycle and Growth

The study used scanning electron microscopy to observe changes in the three-dimensional structure of collagen fibrils in the mink dermis during the hair cycle and growth. It found that during the resting phase, the collagen fibril bundles were dense with small gaps, resulting in a thinner dermal layer, while in the active phase, the bundles were looser with larger gaps, leading to a thicker dermal layer. The size of the connective tissue hair follicle openings increased with mink growth and was larger in the active phase compared to the resting phase, while the density of these openings decreased with growth. Collagen fibrils thickened and their density increased as minks grew. Most collagen fibril bundles in the dermis were oriented perpendicular to the body axis, and the subcutaneous fat layer's collagen fibrils were felt-like, with a unique inner longitudinal and outer circular structure in the connective tissue hair follicles.