Lavker R M, Zheng P S, Dong G
Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia.
Clin Geriatr Med. 1989 Feb;5(1):53-67.
Despite an overall thinning of the epidermis and focal areas of cytologic atypia, there was no morphologic evidence that the protective function of this tissue was compromised by age. The characteristic morphologic markers associated with the keratinization process were not altered either in appearance or in amounts. A well-formed stratum corneum was present, suggestive that barrier ability is not compromised in senile skin. Whereas alterations in the aged epidermis are slight, the dermal-epidermal changes are marked and have greater physiologic consequences. The major change is a relatively flat dermal-epidermal junction because of retraction of the epidermal papillae as well as the microprojections of basal cells into the dermis. This flattening results in a more fragile tissue that is less resistant to shearing forces. Retraction of the epidermal downgrowths may also explain the loss in proliferative capacity associated with the aged epidermis. The major alterations in the aged dermis concern the architecture of the collagen and elastin networks. Both fibrous components appear more compact because of a decrease in the voids or spaces between the fibers; the spaces resulted from a loss of ground substance. Collagen bundles appear to unravel, and the individual elastic fibers show signs of elastolysis. The net effect of these fibrous rearrangements and alterations is a dermis that is less stretchable, less resilient, more lax, and prone to wrinkling.
尽管表皮整体变薄且存在局灶性细胞异型性区域，但没有形态学证据表明该组织的保护功能因年龄而受损。与角质化过程相关的特征性形态学标志物在外观或数量上均未改变。存在结构良好的角质层，提示老年皮肤的屏障能力未受损。虽然老年表皮的改变轻微，但真皮 - 表皮变化明显且具有更大的生理后果。主要变化是真皮 - 表皮连接相对平坦，这是由于表皮乳头回缩以及基底细胞向真皮内的微突起减少所致。这种扁平化导致组织更脆弱，对剪切力的抵抗力降低。表皮向下生长的回缩也可能解释了与老年表皮相关的增殖能力丧失。老年真皮的主要改变涉及胶原蛋白和弹性蛋白网络的结构。由于纤维之间的空隙或间隙减少（空隙是由基质丧失导致的），两种纤维成分看起来更紧密；胶原束似乎散开，单个弹性纤维显示出弹性溶解的迹象。这些纤维重排和改变的最终结果是真皮的伸展性降低、弹性降低、更松弛且易于起皱。
