健康儿童发育过程中头发超微结构的初步研究

目的 对不同年龄儿童头发表面和横断面的形态结构进行检测分析，从超微结构方面了解出生后小儿头发的发育成熟过程和状况。 方法 健康儿童按年龄分为婴儿期组（< 1岁）、幼儿期组（1 ~ 2岁）和学龄前期组（3 ~ 5岁），每组各30例。在顶部、颞部和枕部三个解剖部位收集样本后，使用场发射扫描电子显微镜检测，以获得毛发表面以及横截面形态学数据，包括头发横截面短径与长径、毛发指数（头发横截面短径与长径的比值）、毛小皮厚度（于毛发横截面测得，每根毛发大约包绕5 ～ 10层毛小皮）和数目（毛干表面每单位长度100 μm内包含的毛小皮游离缘数目）以及毛小皮形态（扁平波形和不规则形）。以方差分析、t检验以及卡方检验对所获得的数据进行统计学分析。 结果 方差分析显示，在相同解剖部位，3个年龄组儿童毛发短径及长径差异有统计学意义（顶部：F = 39.67、28.32，均P ＜ 0.01；颞部：F = 13.12、11.91，均P ＜ 0.01；枕部：F = 18.41、16.43，均P ＜ 0.01），数值随着年龄增长而增大，而毛发指数没有改变。顶部头发毛小皮厚度在3个年龄组差异有统计学意义（F = 6.15，P < 0.01），顶、颞、枕3个部位头发的毛小皮数目在3个年龄组的差异均有统计学意义（F值分别为3.29、3.36、3.48，均P ＜ 0.05）。多重比较（LSD方法）分析表明，在婴儿期组与幼儿期组、婴儿期组与学龄前期组间，儿童毛发的短径及长径差异均有统计学意义（均P ＜ 0.001），学龄前期组儿童顶部毛小皮厚度（0.59 ± 0.09 μm）较婴儿期组（0.49 ± 0.08 μm）增加（P = 0.003），顶、颞、枕3个部位毛发的毛小皮数目在学龄前期组均较婴儿期组减少（均P ＜ 0.05）。在相同部位男女性别之间所测毛发短径及长径、毛发指数、毛小皮厚度和数目差异均无统计学意义。两种鳞片形态在3个年龄组间的分布差异无统计学意义。 结论 毛发直径随着儿童的生长发育而增大，毛小皮厚度存在上升趋势，而鳞片数目则具有下降的趋势。

Ultrastructure of hairs in healthy children during development: a preliminary study

Feng Hua*, Liu Tiebing, Hu Yahong, Wang Tinglin, Xu Hongjun, Wang Jianlei, Lin Qiulan, Wang Qi. *Department of Dermatology, Civil Aviation General Hospital, Beijing 100123, China. Corresponding author: Feng Hua, Email: 13311063416@189.cn 【Abstract】 Objective To characterize the morphology and structure of hair surfaces and cross sections in children of different ages, and to understand the development and maturation processes and status of hairs in terms of ultrastructure in healthy children after birth. Methods Ninety healthy child volunteers were equally classified into 3 groups: infancy group （aged less than 1 year）, toddler group （aged 1 - 2 years）, and preschool-age group （aged 3 - 5 years）. Hair samples were collected from the vertex, tempus, and occiput of each child. Field emission scanning electron microscopy was performed to obtain morphological data on surfaces and cross sections of hairs, including minimal and maximal hair diameters, hair index （the ratio of minimal to maximal diameter of hairs）, hair cuticle thickness （measured on hair cross sections, each hair has 5 - 10 layers of cuticles）, hair cuticle count （the number of cuticles per 100 μm length of hair shaft） and pattern （flat waveform or irregular shape）. Statistical analysis was carried out by using analysis of variance, t test, chi-square test, and least significant difference （LSD） test with SPSS19.0 software. Results The minimal and maximal cross-sectional diameters of hairs significantly differed between the three age groups at the same anatomic site （vertex: F = 39.67, 28.32, respectively, both P < 0.01; tempus: F = 13.12, 11.91, respectively, both P < 0.01; occiput: F = 18.41, 16.43, respectively, both P < 0.01）, and increased with age, while no significant changes occurred in hair index with age. Meanwhile, significant differences were observed between the three age groups in the thickness of hair cuticles on the vertex （F = 6.15, P < 0.01）, and in the number of hair cuticles on the vertex, tempus, and occiput （F = 3.29, 3.36 and 3.48 respectively, all P < 0.05）. LSD test showed a significant difference in minimal and maximal hair diameters between the infancy group and toddler group and between the infancy group and preschool-age group （all P < 0.001）, an elevation in the thickness of hair cuticles on the vertex in the preschool-age group compared with the infancy group （0.59 ± 0.09 vs. 0.49 ± 0.08 μm, P = 0.003）, but a decrease in the number of hair cuticles on the vertex, tempus and occiput in the preschool-age group compared with the infancy group （all P < 0.05）. No significant differences were observed between male and female volunteers in minimal and maximal hair diameters, hair index or hair cuticle thickness and number at the same anatomic site. In addition, there were no significant differences in the distribution of the two hair cuticle patterns between the three age groups. Conclusions Hair diameter and cuticle thickness both increase, while hair cuticle number decreases, with the development of children.