BIO210Y5 Lecture Notes - Lecture 3: Red Color, Psoriasis, Mast Cell
17 Jan 2016
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Document Summary
Hair structure: medulla or core of hair contains flexible soft keratin, cortex contains hard layer of keratin( gives hair its stiffness, cuticle thin, very tough, contains hard keratin. A hair in scalp grows 2-5 years. Variations in growth rate & in duration of hair growth cycle account for individual dofferences in the length of uncut hair. Variations in hair color reflect differences in structure + variations in pigment produced by melanocytes. Different forms of melanin give a dark brown, yellow-brown or red color to hair. As pigment production decreases with age hair color lightens. White hair combination of lack of pigment + presence of air bubbles in the medulla of hair shaft. Discharge an oily lipid secretion into hair follicles. The glands that communicate with single hair follicle share a single duct. Lipids released from gland cells enter lumen. Arrector pilli contracts, squeezing the sebaceous gland & forcing its secretory product into the hair follicle.
