1. SHUMEZ. H

2. Hair is a cutaneous appendagetypical of mammalian skin. It has no vital function inhumans, yet its psychologicalfunctions are extremely important. 3. TYPES OF HAIR LANUGO (wool like)Fine, soft, unmedullated, unpigmented VELLUS HAIR ( 0.03 mm )Soft, unmedullated, pigmented TERMINAL HAIR ( 0.06 mm )Coarse, medullated, pigmented 4. DISTRIBUTION Cheek - 830/450/sq. cm Forehead- 765/sq. cm Scalp - 350/sq. cm Chest & limbs - 50 100/sq. cm 5. ANATOMYMature hair follicle divided into UPPER SEGMENTInfundibulumIsthmus LOWER SEGMENTStemBulb 6. INFUNDIBULUM Extends from Skin surface (Ostium)above to the entry of Sebaceous ductbelow. Lining is similar to the surfaceepidermis. 7. ISTHMUS Extends from entry of Sebaceous ductabove to attachment of Arrectormuscle below. Narrow part of the hair follicle. Hair shaft is fully keratinized. Inner root sheath begins todisintegrate. 8. STEM Longest part of hair follicle. Extends from insertion of Arrector pilimuscle above upto the keratogenouszone. Consists of 3 layers :Outer root sheathInner root sheathHair shaft 9. BULB Lower most part of hair follicle. Follicular papilla lies in the center ofthe follicular bulb. The bulk of the follicular bulb isformed of Epithelial matrix ( matricalcells ). Few melanocytes are interspersed. 10. ADAMSONS FRINGE Upper part of the bulb. Keratogenous zone. Divided into 6 layers:MedullaCortexHair cuticleCuticle of inner sheathHuxleys layerHenles layer 11. FOLLICULAR PAPILLA Varies according to the phase of haircycle. Composed of specialized fibroblast likecells embedded in extracellular matrix. Often contains a loop of capillary bloodvessels. Volume of dermal papilla mayberesponsible for controlling size of hairfollicle. 12. HAIR SHAFT 3 layers :MEDULLACORTEXHAIR CUTICLE Medulla is a variable structure. Maybe continuous, interrupted or absent. Contains few layers of rounded cells containing glycogen. 13. Cortex forms bulk of the hair shaft. Consists of numerous layers offlattened elongated cells packedtogether. Cell organelles and nuclei disappearas the cells keratinize. 14. Hair cuticle consists of 5 10 layers offlattened cells arranged inoverlapping roof tile pattern. The upwards pointing edges of thehair cuticle interlock with thedownwards pointing edges of cuticleof inner sheath. 15. INNER ROOT SHEATH 3 layers :CuticleHuxleys layerHenles layer Henle s layer 2 cells thick, keratinizesfirst Huxleys layer 4-6 cells thick At the Isthmus the IRS disintegrates . 16. OUTER ROOT SHEATH Most peripheral part of hair follicle. Single layered at lower tip of hair bulband 4-6 layered at the isthmus. Keratinize at the level of Isthmus. Trichilemmal keratinization. Occasionally companion layer maybeseen in between IRS and ORS. 17. PERIFOLLICULAR FIBROUS SHEATH Thin layer of connective tissue whichenvelopes the hair follicle througout itslength. PFS is variable: Early Anagen : Thin, containing collagenand fibroblasts Anagen : Thickened and trilayered Catagen : Hyalinization of PFS Telogen : Thinning of PFS 18. ULTRASTRUCTURE Hair is formed of hard keratin with highsulfur content. High sulfur content responsible for itsextraordinary tensile strength. Fibrillar component consists ofmacrofibrils, 7 nm thick arranged inlongitudinal lamellated form. S-H linkages of cysteine at the bulb areconverted to S-S linkages of cysteinehigher up. 19. HAIR FOLLICLE INNERVATION A plexus of longitudinally arrangedsensory nerve fibres surrounds theisthmus region. Other nerve endings found are :Free nerve endingsPilo Ruffini nerve endingsMerkel nerve endings 20. HAIR CYCLE Hair follicles undergo a repetitive sequenceof growth and rest known as hair cycle. Hair cycle varies between follicles indifferent regions of the skin in the samespecies . Hair growth occurs in 3 stages : Anagen Catagen Telogen 21. ANAGEN Period of active hair growth. Duration of this phase responible forfinal length of the hair. Usually lasts for 2 3 years. Duration of Anagen geneticallydetermined. About 85% of all hairs are in this phaseat any time. 22. Onset of mitotic activity in epithelialcells of Dermal papilla. Lower part of follicle elongatesdownwards along a preformed dermaltract ( stele ). Dermal papilla expands from a tightlypacked ball of cells into a flask shapedstructure. A network of capillary blood vesselsdevelop around the lengthening follicle. 23. Epithelial cells in the hair bulb undergovigorous proliferative activity. The melanocytes become active addingcolour to this newly forming hair. Anagen consists of 6 substages. Differences in the length of hair is dueto variable duration of the last stage ( VI). 24. CATAGENShort transition stage that occurs atthe end of the anagen phase. Signals the end of active growth ofhair. Usually lasts about 2 3 weeks. 25. At the end of Anagen, epithelial divisiondeclines and ceases. Proximal end of the hair shaft keratinizes toform a club shaped structure. Lower part of the follicle involutes byapoptosis. Basement membrane surrounding the folliclebecomes thickened to form glassymembrane. Base of the follicle along with dermal papillamoves upwards to lie below the level ofArrector muscle attachment. 26. TELOGEN Resting phase of the hair follicle. Usually lasts for about 3 months. About 10 15% of all hairs are in this phase at any time. 27. Quiscient period betweencompletion of follicular regressionand onset of next anagen phase. Resting club hair lies within anepithelial sac. Streak of fibrous tissue extends frombase of follicle to quiscient papillabeneath fibrous tract 28. EXOGEN / TELOPTOSIS Active process of shedding of clubhair. Defective Exogen gives rise toTrichostasis spinulosa. 29. KENOGEN / LAG PHASE Latent phase in the hair cycle wherehair follicle is empty after hairshedding and persists in this stagefor a variable duration. Seen in patients with AGA andprepubertal children. 30. Approx. 100000 follicles are presenton the average scalp. About 70 100 hairs in telogen areshed daily. Hair on the scalp grows at anaverage rate of 0.45 mm daily. It grows faster on the crown > vertex> temple. 31. FUNCTIONS OF HAIR Tactile perception Protection of scalp from sunlight andtrauma. Protection of eyes from foreign bodies. Screening nasal passages. Reduce friction in intertriginous areas. 32. ANDROGENS Follicles that respond to androgen aregrouped as androgen dependent hair. Converts axillary and pubic folliclesinto terminal follicles. Similar course in beard, moustache,abdomen, chest area in men. Increases the duration of anagen hencethickness of hair shaft. Increases size of hair follicle. 33. However, Scalp hair respond in aregressive manner to androgens. Pubertal recession of frontal hair in boysand are resposible for AGA. Enzyme 5 reductase is responsible forconversion of weaker androgens intomore potent form. Finasteride inhibits 5 reductase type 2and prevents AGA. 34. Growth Hormone - synergistic effecton androgen dependent hair. Estrogen - retains club hair in follicle. Prolactin - androgen like effect. Throid hormone - Both hypo andhypersecretion can cause alopecia.Retards the rate of hair growth.Retains club hair in the follicle. 35. IGF I : promotes hair growth andproliferation. Insulin - acts through IGF I andpromotes hair growth. Cortisol - enhances proliferative actionsof IGF I Shaving has no effect on the rate of hair growth. 36. DURING PREGNANCY Increase in proportion of follicles inanagen. Reduction in hair density. Post partum - large number of follicles enter into telogen, leading to increased shedding - Postpartum telogen effluvium 37. MOLECULAR CONTROL OF HAIRCYCLING ANAGEN Activation of various mediators - IGF 1, HGF, SHH, Whn, beta catenin IGF 1 plays an important role. It promotes hair growth and proliferation. IGF 1 receptors are located in dermalpapilla and ORS. Insulin acts through IGF 1 and promotehair growth. 38. CATAGEN It is marked by down regulation of IGF 1 receptors and HGF expression in hairbulb. TGF , IL 1, TNF are themediators of catagen activation. Stress, trauma, dexamethasone, ACTH, estradiol also initiate catagen phase. 39. TELOGEN Bone morphogenetic protein 4 plays an important role in suppressing follicular growth and differentiation. BMP 4 acts on BMPR IA expressed by keratinocytes. BMP 4 antagonist Noggin accelerates the onset of anagen. 40. COMMON CAUSES OF HAIRFALL Androgenetic Alopecia Alopecia areata Infection Postpartum Hypothyroidism Hyperthyroidism Stress 41. Inadequate diet Low serum iron Major surgery / chronic illness Fungal infection of scalp Trichotillomania Oral contraceptives Chemotherapy Other drugs Vit. A, blockers, Antidepressants, Anticoagulants, etc. 42. CAUSES OF HYERTRICHOSIS Hypertrichosis lanuginosa Naevoid hypertrichosis Hypo/hyperthyroidism Anorexia nervosa Dermatomyositis Epidermolysis bullosa Porphyria Drugs Systemic steroid, minoxidil, psoralen, diazoxide, cyclo 43. CAUSES OF HIRSUTISM Polycystic Ovarian Disease Ovarian tumours SAHA syndrome Congenital Adrenal Hyperplasia Hyperprolactinaemia Adrenocortical disease Idiopathic hirsutism Drugs phenytoin, androgens, OCPs, diazoxide, minoxidil.