Human vs. Animal Hair

HUMAN MEDULLA A human medulla is different from an animal medulla. The medulla is the center part of the hair shaft.

The human medulla may be fragmented, absent or continuous.

Medullary Index The index is calculated by measuring the diameter of the medulla and dividing it by the diameter of the hair. The Medullary Index for animal hair is usually greater than 1/2. The Medullary Index for human hair is generally less than 1/3.

Animal hairs are classified into three basic types. Guard hairs: form the outer coat of an animal and provide protection Fur or wool hairs: form the inner coat of an animal and provide insulation Tactile hairs: (whiskers) found on the head of animals and provide sensory functions http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research02.htm

Comparison Human Animal Consistent in color and pigmentation throughout the length of the hair shaft. May exhibit radical color changes in a short distance called banding. Evenly distributed, or slightly more dense toward the cuticle. More centrally distributed, more dense toward the medulla. The medulla is generally less than one-third the overall diameter of the hair shaft. The medulla is generally more than one-half the overall diameter of the hair shaft. The root is commonly club-shaped. The roots are highly variable between animals. The scale pattern of the cuticle in human hairs is most commonly imbricate. The scale pattern is highly variable between animals. The shape of the hair shaft is most often cylindrical. The shape of the hair shaft is also more variable in animal hairs.

Human Hair

Cat Hair

Bat Hair

Rat Hair

Dog Hair

Horse Hair Human Hair Horse Hair

Rabbit Medulla uni-serial ladder (in guard hair) multi-serial Medullas are different depending on the type (location) of hair.