Anagen Phase
Definition
The actively growing phase of the hair follicle, during which the keratinocyte is in contact with the dermal papilla capillary and incorporates whatever drugs are in circulation. Around 85 to 90 percent of scalp follicles are in anagen at any given time, which is why scalp hair is the standard collection site for chronic exposure work.
Related terms
- Cut-Off Concentration
- The threshold analyte concentration, set by regulatory guidance, above which a specimen is reported as a screen-positive. Choosing the cut-off balances sensitivity...
- Decontamination Wash
- A multi-solvent surface wash (typically dichloromethane, methanol and aqueous buffer) applied before digestion to strip externally deposited drug from the cuticle. The...
- External Contamination
- The presence of a drug or substance on the outer surface of the hair shaft from environmental exposure rather than systemic ingestion....
- Hair Shaft Cortex
- The main structural layer of the hair shaft, composed of tightly packed keratin filaments. It contains the melanin granules responsible for hair...
- Melanin Binding
- The non-covalent association of basic and lipophilic drugs (cocaine, opiates, amphetamines, nicotine) with melanin granules in the hair cortex. Pigmented (black, brown)...
- Mitochondrial DNA (mtDNA)
- DNA located in mitochondria rather than the cell nucleus. Present in hundreds to thousands of copies per cell, making it recoverable from...
- Parent-to-Metabolite Ratio
- The ratio of an intact drug to its in vivo metabolite in hair, used to distinguish genuine ingestion (which produces both) from...
- Segmental Analysis
- The practice of cutting collected hair into sequential 1 cm lengths from the root end and analysing each segment separately. Each centimetre...
- Segmental Hair Analysis
- The practice of cutting a hair strand into consecutive segments (typically 1 cm each) and analysing each segment separately. Because hair grows...
- Short Tandem Repeat (STR)
- Short repetitive DNA sequences scattered throughout the genome, with the number of repeats varying between individuals at each locus. DNA profiling compares...
Explained in these topics
- Hair Analysis for Drugs and Chronic PoisoningThe actively growing phase of the hair follicle, during which the keratinocyte is in contact with the dermal papilla capillary and incorporates whatever drugs...
- Hair as a Source of DNA and Toxicological InformationThe active growth phase of the hair follicle, during which the dermal papilla produces nucleated cells that differentiate into the hair shaft. Only anagen-phas...