Anatomy & SciencesQuestion 461 of 484

Which list correctly orders the three layers of the hair shaft from the OUTSIDE in?

a.Medulla, cortex, cuticle
b.Cortex, medulla, cuticle
c.Cuticle (outer overlapping scales), cortex (middle, with pigment and keratin fibers; the strongest layer that gives hair color and elasticity), medulla (innermost core, often absent in very fine hair)
d.Cuticle, medulla, cortex

Explanation

From outside to inside the hair shaft is: CUTICLE (overlapping translucent keratin scales that protect the strand and reflect light when smooth), CORTEX (the bulky middle layer containing the keratin fiber bundles, melanin pigment, and most of the side bonds; responsible for strength, elasticity, and color), and MEDULLA (the innermost honeycomb-like core, sometimes fragmentary or absent, especially in fine or blonde hair). Chemical services target the cortex but must first pass through the cuticle. Cosmetologists rely on this anatomy daily under the general competence duties at Bus. & Prof. Code §7320. Options A, B, and D scramble the order in ways the exam tests directly.

Law Reference: Bus. & Prof. Code §7320

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