Hutchinson P E, Thompson J R
Department of Dermatology, Leicester Royal Infirmary, Leicester LE1 5WW, UK.
Br J Dermatol. 1999 Mar;140(3):438-45. doi: 10.1046/j.1365-2133.1999.02706.x.
Hairs were sampled from long-haired Caucasian females, and cross-sectional measurements were performed using a rotating profile method at fixed humidity (100%). The effect of the hair cycle on medullation was investigated by examining medulla size and form along the lengths of anagen and telogen terminal hairs and also from a composite model of the entire medulla, as produced from a full cycle's growth, by amalgamating the results from the anagen and telogen hairs. The effect of hair shaft cross-sectional size on medullation has been investigated by controlling any effect of the hair cycle on terminal hairs and by use of the maximal medulla size in short, fine (vellous) hairs from the same subjects. All terminal hairs were medullated for the majority of their lengths. The presence and size of the medulla, in terminal hairs, was profoundly affected by the hair cycle. It was largest early in anagen, where the medulla minor axis, major axis and cross-sectional area represented about 26%, 23% and 7% of the corresponding whole hair shaft parameters (at 100% humidity). The medulla was virtually absent towards the end of anagen. The shape of the medulla cross-section was less elliptical than that of the whole hair shaft and was close to circular. There was no significant change in medulla shape through anagen. The form of the medulla was also affected by the hair cycle; approximately, it was continuous for the first 50% of anagen, discontinuous for the next 25% and virtually absent or absent for the final 25%. The maximal size of the medulla, as occurred in early anagen, was markedly associated with the cross-sectional size of the whole hair shaft, both within terminal hairs and between all scalp hairs. The medulla was large in terminal hairs and small or absent in very small hairs. The proportion of the whole hair shaft occupied by the medulla increased with increase in hair size and reached a maximum in terminal hairs, in which the medulla minor axis represented about 30% of the whole hair shaft minor axis. Furthermore, this proportion was constant in the terminal hairs and was not related to whole hair shaft size. Such maximal proportional medullation might represent a defining feature of terminal hairs. Variation in size of the medulla is not the cause of the previously reported cycle-dependent change in cross-sectional size of the whole hair shaft of terminal hairs.
从长发白人女性中采集毛发样本，在固定湿度（100%）下采用旋转轮廓法进行横截面测量。通过检查生长期和休止期终毛长度上的髓质大小和形态，以及通过合并生长期和休止期毛发的结果构建的整个髓质的复合模型（来自一个完整周期的生长），研究毛发周期对髓质形成的影响。通过控制毛发周期对终毛的任何影响，并使用来自同一受试者的短而细（毳毛）毛发中的最大髓质大小，研究毛干横截面大小对髓质形成的影响。所有终毛在其大部分长度上都有髓质。终毛中髓质的存在和大小受到毛发周期的深刻影响。在生长期早期髓质最大，此时髓质短轴、长轴和横截面积分别约占相应整个毛干参数的26%、23%和7%（在100%湿度下）。在生长期接近结束时髓质几乎不存在。髓质横截面的形状比整个毛干的形状椭圆度小，接近圆形。在生长期内髓质形状没有显著变化。髓质的形态也受到毛发周期的影响；大致来说，在生长期的前50%是连续的，接下来的25%是不连续的，在最后25%几乎不存在或不存在。在生长期早期出现的髓质最大尺寸，与整个毛干的横截面大小显著相关，无论是在终毛内部还是在所有头皮毛发之间。终毛中的髓质大，非常小的毛发中的髓质小或不存在。髓质占整个毛干的比例随着毛发大小的增加而增加，在终毛中达到最大值，其中髓质短轴约占整个毛干短轴的30%。此外，这个比例在终毛中是恒定的，与整个毛干大小无关。这种最大比例的髓质形成可能代表终毛的一个决定性特征。髓质大小的变化不是先前报道的终毛整个毛干横截面大小的周期依赖性变化的原因。
