The intrinsic changes are best seen in places where there has been minimum light exposure. The upper inner arm and covered buttocks are good examples. Here the top layer of the skin (epidermis) is thinned only slightly. Its cells do not adhere as well as in younger skin, and there is comparatively increased architectural irregularity. The number of pigmentary cells (melanocytes) is reduced, and the junction with the dermis (underlayer of the skin) shows some degree of flattening.
The dermis itself shows a thinning (atrophy) in which its major fibrous and cellular components are diminished. The number of sweat glands is reduced. Hair is grayer, and its individual diameters are narrower. In addition, the hair roots (follicles) on the scalp and face are fewer but the associated ‘‘grease’’ (sebaceous) glands are larger. Nails become fragile and develop longitudinal lines. The subcutaneous tissue under the dermis is thinner about the face, hands, shins, and feet but thicker on the waists of men and the thighs of women.
Coarse skin folds emphasize expression lines. They follow the contour of the larger muscles of the face.
The physiological activity of the various skin elements is generally reduced. This applies particularly to the immune response, the response to injury, cellular replacement, glandular activity, heat regulation, and sense of touch.
The effect on the individual can be summed up as the minor nuisances of old age and but mainly harmless. It is the external influence that is potentially harmful.