A human head hair is best characterized by: a. The absence of a cortex. b. Its scale pattern. c. A medulla that is more than 1/2 the overall diameter of the hair shaft. d. A medulla that is absent or is less than 1/3 the overall diameter of the hair shaft.

d. A medulla that is absent or is less than 1/3 the overall diameter of the hair shaft is the correct answer.

Explanation:

A human head hair is best characterized by a medulla that is absent or is less than 1/3 the overall diameter of the hair shaft. Hair is a protein thread that develops from the follicles located within the dermis. Hair present on the head acts as a source of insulation, protect from the ultraviolet radiation and dust.

Hair consists of two different parts

Follicle Hair shaft

hair shaft consists:

cortex: located between hair cuticle and medulla cuticle cells: are the outermost portion of the hair shaft. medulla: is the inner layer of the hair.