Hair 1 Biology of Hair Hair is composed

Hair 1

Biology of Hair • Hair is composed of the protein keratin • Hair is produced from the hair follicle – Hair follicles are developed during fetal development and no new follicles are produced after birth 2

Hair Follicles • A follicle is a deep pit where hair grows. • The shaft of a hair is above the skin surface • The root is below the skin surface. 3

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Hair Structure • Cuticle: outermost layer of the hair • Cortext: hard core that gives hair its stiffness • Medula: soft inner core of hair 5

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Hair structure continued… • Arrector Pili: muscle attached to hair • Raises hairs • Response to fright or cold • Sebaceous Glands: • connected to hair follicles • secretes an oil called sebum 7

Senses in the Hair • Hairs are sensory organs with nerve endings located around the roots • hairs act as tiny triggers to indicate when an object is in close contact with the body 8

Hair Growth • Your hair grows at an average rate of 0. 3 mm per day 9

Reasons for Hair • Hair can have different jobs: – Warmth: hair on your head keeps it warm, – Protection: eye lashes and eyebrows protect your eyes 10

Location of Hair • Your lips, palms of hands and soles of feet don’t have any hair – the rest of the body does, but it is not always easily visible 11

Hair Facts • You have more than 100 000 hairs on your head • about 50 -100 fall out each day from brushing, washing etc 12

Different Hair Types • Hair follicles determine whether you will have straight or curly hair, and whether you will have coarse, thick hair, or thin and fine – Someone with ‘thick’ hair literally has thicker strands of hair than someone with thin hair • Hair is coloured by melanin (lighter hair = less melanin) 13

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Hair Loss • Permanent hair loss or baldness is more common in men • Hair loss progresses with age 15

Hair Loss • Hair loss may be affected by the hormone testosterone • Can b also be caused by – illness – poor circulation to the hair follicles – infections of the scalp – some types of shampoo 16

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