trichoblasts

Trichoblasts are specialized cells with relevance in both human biology and plant botany. In animals, a trichoblast is a precursor cell in the hair follicle lineage. During skin development, a subset of basal epidermal cells forms a placode that invaginates to become a hair germ. The cells of the hair germ, termed trichoblasts, proliferate and organize into the hair matrix, which produces the hair shaft and inner root sheath. The surrounding outer root sheath and signals from the dermal papilla guide follicle growth, cycling, and differentiation. Trichoblasts thus play a central role in establishing and maintaining hair follicles, influencing characteristics such as density, texture, and cycle duration.

In botany, trichoblasts are epidermal cells that differentiate into root hairs or foliar trichomes. In roots they develop into root hair cells that extend tubular extensions, increasing surface area for water and nutrient uptake. In aerial tissues, trichoblasts can form leaf or stem trichomes that serve protective, reflective, or secretory functions. Trichoblasts arise from the epidermal layer in a position-dependent manner and often undergo asymmetric cell division to generate a hair-forming lineage.

In pathology, neoplasms known as trichoblastomas arise from follicle-differentiated trichoblasts and are characterized by structural resemblance to developing hair follicles; they are distinguished from malignant basal cell carcinomas by patterns of differentiation and stromal features.

See also: hair follicle, root hair, trichome, trichoblastoma.