2:28:12 - CHE113 Nicolas Canel 2/28/12 Hair Morphology Each...

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CHE113 Nicolas Canel 2/28/12 Hair Morphology Each individual hair fiber, has a muscle that can cause the hair to stand up when cold, and lay down when hot. The outside is the cuticle Look at hair fibers in terms of physical structure Best ways to identify hair medulla and cuticle Cortex – inner part Cuticle- protective outer part Medulla - Cuticle - scales on exterior of hair shaft (keratinized). Cortex - main body of shaft, contains pigment granules, shape. Medulla - either absent or ca. 1/3 the diameter of the shaft (continuous, interrupted, segmented or absent). Other animals have different properties - Cuticle and Medulla are best used to distinguish if the sample is human or animal. Medulla vary from person to person AND even among hairs from one person. Three main Medulla types: continuous, interrupted and fragmented. Growth Phases: –Anagen - initial phase where hair actively grows. –Catagen - transition between active and loss stage - slowed growth. –Telogen - final phase resulting in hair loss. In humans these phases are randomly happening. Anagen - up to 6 years (or as short as 3 mo. for eyelashes or arms). Length of anagen determine max. hair length. Have about 100,000 head hairs. Catagen - usually up to several weeks. Telogen - up to 6 months. Animals that shed sychronize the telogen phases. Hair grows fairly uniformly at 0.5 mm/day (ca. 6 in./year). 75% of adult females say they color their hair (7% in 1950). Most popular current color is red. Permanent coloring requires chemicals to reach into the cortex (through the cuticle). There they react with the cuticle, changing the color and becoming too large to be washed from the hair. Hair color
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This note was uploaded on 03/02/2012 for the course CHE 113 taught by Professor Spencer during the Spring '08 term at Syracuse.

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2:28:12 - CHE113 Nicolas Canel 2/28/12 Hair Morphology Each...

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