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SHUMEZ. H
 Hair is a cutaneous appendage  typical of mammalian skin. It has no vital function in  humans, yet its psychological  f...
TYPES OF HAIR LANUGO (wool like)  Fine, soft, unmedullated, unpigmented VELLUS HAIR ( ≤0.03 mm )  Soft, unmedullated, pi...
DISTRIBUTION Cheek           -   830/450/sq. cm Forehead        -   765/sq. cm Scalp           -   350/sq. cm Chest & ...
ANATOMYMature hair follicle divided into UPPER SEGMENT  Infundibulum  Isthmus LOWER SEGMENT  Stem  Bulb
INFUNDIBULUM Extends from Skin surface (Ostium)  above to the entry of Sebaceous duct  below. Lining is similar to the s...
ISTHMUS Extends from entry of Sebaceous duct  above to attachment of Arrector  muscle below. Narrow part of the hair fol...
STEM Longest part of hair follicle. Extends from insertion of Arrector pili  muscle above upto the keratogenous  zone. ...
BULB Lower most part of hair follicle. Follicular papilla lies in the center of  the follicular bulb. The bulk of the f...
ADAMSON’S FRINGE Upper part of the bulb. Keratogenous zone. Divided into 6 layers:  Medulla  Cortex  Hair cuticle  Cuti...
FOLLICULAR PAPILLA Varies according to the phase of hair  cycle. Composed of specialized fibroblast like  cells embedded...
HAIR SHAFT 3 layers :  MEDULLA  CORTEX  HAIR CUTICLE Medulla is a variable structure. Maybe continuous, interrupted or ...
 Cortex forms bulk of the hair shaft. Consists of numerous layers of  flattened elongated cells packed  together. Cell ...
 Hair cuticle consists of 5 – 10 layers of  flattened cells arranged in  overlapping “roof – tile” pattern. The upwards ...
INNER ROOT SHEATH 3 layers :    Cuticle    Huxley’s layer    Henle’s layer Henle’ s layer – 2 cells thick, keratinizes  ...
OUTER ROOT SHEATH Most peripheral part of hair follicle. Single layered at lower tip of hair bulb  and 4-6 layered at th...
PERIFOLLICULAR FIBROUS SHEATH Thin layer of connective tissue which  envelopes the hair follicle througout its  length. ...
ULTRASTRUCTURE Hair is formed of hard keratin with high  sulfur content. High sulfur content responsible for its  extrao...
HAIR FOLLICLE INNERVATION A plexus of longitudinally arranged  sensory nerve fibres surrounds the  isthmus region. Other...
HAIR CYCLE Hair follicles undergo a repetitive sequence  of growth and rest known as hair cycle. Hair cycle varies betwe...
ANAGEN Period of active hair growth. Duration of this phase responible for  final length of the hair. Usually lasts for...
 Onset of mitotic activity in epithelial  cells of Dermal papilla. Lower part of follicle elongates  downwards along a p...
 Epithelial cells in the hair bulb undergo  vigorous proliferative activity. The melanocytes become active adding  colou...
CATAGEN  Short transition stage that occurs at  the end of the anagen phase. Signals the end of active growth of  hair....
 At the end of Anagen, epithelial division  declines and ceases. Proximal end of the hair shaft keratinizes to  form a c...
TELOGEN Resting phase of the hair follicle. Usually lasts for about 3 months. About 10 – 15% of all hairs are in this p...
 Quiscient period between  completion of follicular regression  and onset of next anagen phase. Resting club hair lies w...
EXOGEN / TELOPTOSIS Active process of shedding of club  hair. Defective Exogen gives rise to  Trichostasis spinulosa.
KENOGEN / LAG PHASE Latent phase in the hair cycle where  hair follicle is empty after hair  shedding and persists in thi...
 Approx. 100000 follicles are present  on the average scalp. About 70 – 100 hairs in telogen are  shed daily. Hair on t...
FUNCTIONS OF HAIR Tactile perception Protection of scalp from sunlight and  trauma. Protection of eyes from foreign bod...
ANDROGENS Follicles that respond to androgen are  grouped as androgen dependent hair. Converts axillary and pubic follic...
 However, Scalp hair respond in a  regressive manner to androgens. Pubertal recession of frontal hair in boys  and are r...
 Growth Hormone - synergistic effect  on androgen dependent hair. Estrogen - retains club hair in follicle. Prolactin -...
 IGF – I : promotes hair growth and  proliferation. Insulin - acts through IGF – I and  promotes hair growth. Cortisol ...
DURING PREGNANCY Increase in proportion of follicles in  anagen. Reduction in hair density. Post partum - large number ...
MOLECULAR CONTROL OF HAIRCYCLING         ANAGEN Activation of various mediators - IGF –  1, HGF, SHH, Whn, beta catenin ...
CATAGEN It is marked by down regulation of IGF –  1 receptors and HGF expression in hair  bulb. TGF – β, IL – α1, TNF – ...
TELOGEN Bone morphogenetic protein – 4 plays an important role in suppressing follicular growth and differentiation. BMP...
COMMON CAUSES OF HAIRFALL Androgenetic Alopecia Alopecia areata Infection Postpartum Hypothyroidism Hyperthyroidism...
 Inadequate diet Low serum iron Major surgery / chronic illness Fungal infection of scalp Trichotillomania Oral cont...
CAUSES OF HYERTRICHOSIS Hypertrichosis lanuginosa Naevoid hypertrichosis Hypo/hyperthyroidism Anorexia nervosa Dermat...
CAUSES OF HIRSUTISM Polycystic Ovarian Disease Ovarian tumours SAHA syndrome Congenital Adrenal Hyperplasia Hyperprol...
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
Structure  of  hair
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Structure of hair

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Transcript of "Structure of hair"

  1. 1. SHUMEZ. H
  2. 2.  Hair is a cutaneous appendage typical of mammalian skin. It has no vital function in humans, yet its psychological functions are extremely important.
  3. 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. 4. DISTRIBUTION Cheek - 830/450/sq. cm Forehead - 765/sq. cm Scalp - 350/sq. cm Chest & limbs - 50 – 100/sq. cm
  5. 5. ANATOMYMature hair follicle divided into UPPER SEGMENT Infundibulum Isthmus LOWER SEGMENT Stem Bulb
  6. 6. INFUNDIBULUM Extends from Skin surface (Ostium) above to the entry of Sebaceous duct below. Lining is similar to the surface epidermis.
  7. 7. ISTHMUS Extends from entry of Sebaceous duct above to attachment of Arrector muscle below. Narrow part of the hair follicle. Hair shaft is fully keratinized. Inner root sheath begins to disintegrate.
  8. 8. STEM Longest part of hair follicle. Extends from insertion of Arrector pili muscle above upto the keratogenous zone. Consists of 3 layers : Outer root sheath Inner root sheath Hair shaft
  9. 9. BULB Lower most part of hair follicle. Follicular papilla lies in the center of the follicular bulb. The bulk of the follicular bulb is formed of Epithelial matrix ( matrical cells ). Few melanocytes are interspersed.
  10. 10. ADAMSON’S FRINGE Upper part of the bulb. Keratogenous zone. Divided into 6 layers: Medulla Cortex Hair cuticle Cuticle of inner sheath Huxley’s layer Henle’s layer
  11. 11. FOLLICULAR PAPILLA Varies according to the phase of hair cycle. Composed of specialized fibroblast like cells embedded in extracellular matrix. Often contains a loop of capillary blood vessels. Volume of dermal papilla maybe responsible for controlling size of hair follicle.
  12. 12. HAIR SHAFT 3 layers : MEDULLA CORTEX HAIR CUTICLE Medulla is a variable structure. Maybe continuous, interrupted or absent. Contains few layers of rounded cells containing glycogen.
  13. 13.  Cortex forms bulk of the hair shaft. Consists of numerous layers of flattened elongated cells packed together. Cell organelles and nuclei disappear as the cells keratinize.
  14. 14.  Hair cuticle consists of 5 – 10 layers of flattened cells arranged in overlapping “roof – tile” pattern. The upwards pointing edges of the hair cuticle interlock with the downwards pointing edges of cuticle of inner sheath.
  15. 15. INNER ROOT SHEATH 3 layers : Cuticle Huxley’s layer Henle’s layer Henle’ s layer – 2 cells thick, keratinizes first Huxley’s layer – 4-6 cells thick At the Isthmus the IRS disintegrates .
  16. 16. OUTER ROOT SHEATH Most peripheral part of hair follicle. Single layered at lower tip of hair bulb and 4-6 layered at the isthmus. Keratinize at the level of Isthmus. Trichilemmal keratinization. Occasionally “companion layer” maybe seen in between IRS and ORS.
  17. 17. PERIFOLLICULAR FIBROUS SHEATH Thin layer of connective tissue which envelopes the hair follicle througout its length. PFS is variable: Early Anagen : Thin, containing collagen and fibroblasts Anagen : Thickened and trilayered Catagen : Hyalinization of PFS Telogen : Thinning of PFS
  18. 18. ULTRASTRUCTURE Hair is formed of hard keratin with high sulfur content. High sulfur content responsible for its extraordinary tensile strength. Fibrillar component consists of macrofibrils, 7 nm thick arranged in longitudinal lamellated form. S-H linkages of cysteine at the bulb are converted to S-S linkages of cysteine higher up.
  19. 19. HAIR FOLLICLE INNERVATION A plexus of longitudinally arranged sensory nerve fibres surrounds the isthmus region. Other nerve endings found are : Free nerve endings Pilo – Ruffini nerve endings Merkel nerve endings
  20. 20. HAIR CYCLE Hair follicles undergo a repetitive sequence of growth and rest known as hair cycle. Hair cycle varies between follicles in different regions of the skin in the same species . Hair growth occurs in 3 stages : Anagen Catagen Telogen
  21. 21. ANAGEN Period of active hair growth. Duration of this phase responible for final length of the hair. Usually lasts for 2 – 3 years. Duration of Anagen genetically determined. About 85% of all hairs are in this phase at any time.
  22. 22.  Onset of mitotic activity in epithelial cells of Dermal papilla. Lower part of follicle elongates downwards along a preformed dermal tract ( stele ). Dermal papilla expands from a tightly packed ball of cells into a flask shaped structure. A network of capillary blood vessels develop around the lengthening follicle.
  23. 23.  Epithelial cells in the hair bulb undergo vigorous proliferative activity. The melanocytes become active adding colour to this newly forming hair. Anagen consists of 6 substages. Differences in the length of hair is due to variable duration of the last stage ( VI ).
  24. 24. CATAGEN Short transition stage that occurs at the end of the anagen phase. Signals the end of active growth of hair. Usually lasts about 2 – 3 weeks.
  25. 25.  At the end of Anagen, epithelial division declines and ceases. Proximal end of the hair shaft keratinizes to form a club shaped structure. Lower part of the follicle involutes by apoptosis. Basement membrane surrounding the follicle becomes thickened to form “glassy membrane”. Base of the follicle along with dermal papilla moves upwards to lie below the level of Arrector muscle attachment.
  26. 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. 27.  Quiscient period between completion of follicular regression and onset of next anagen phase. Resting club hair lies within an epithelial sac. Streak of fibrous tissue extends from base of follicle to quiscient papilla beneath – fibrous tract
  28. 28. EXOGEN / TELOPTOSIS Active process of shedding of club hair. Defective Exogen gives rise to Trichostasis spinulosa.
  29. 29. KENOGEN / LAG PHASE Latent phase in the hair cycle where hair follicle is empty after hair shedding and persists in this stage for a variable duration. Seen in patients with AGA and prepubertal children.
  30. 30.  Approx. 100000 follicles are present on the average scalp. About 70 – 100 hairs in telogen are shed daily. Hair on the scalp grows at an average rate of 0.45 mm daily. It grows faster on the crown > vertex > temple.
  31. 31. FUNCTIONS OF HAIR Tactile perception Protection of scalp from sunlight and trauma. Protection of eyes from foreign bodies. Screening nasal passages. Reduce friction in intertriginous areas.
  32. 32. ANDROGENS Follicles that respond to androgen are grouped as androgen dependent hair. Converts axillary and pubic follicles into terminal follicles. Similar course in beard, moustache, abdomen, chest area in men. Increases the duration of anagen hence thickness of hair shaft. Increases size of hair follicle.
  33. 33.  However, Scalp hair respond in a regressive manner to androgens. Pubertal recession of frontal hair in boys and are resposible for AGA. Enzyme 5α reductase is responsible for conversion of weaker androgens into more potent form. Finasteride inhibits 5α reductase type 2 and prevents AGA.
  34. 34.  Growth Hormone - synergistic effect on androgen dependent hair. Estrogen - retains club hair in follicle. Prolactin - androgen like effect. Throid hormone - Both hypo and hypersecretion can cause alopecia. Retards the rate of hair growth. Retains club hair in the follicle.
  35. 35.  IGF – I : promotes hair growth and proliferation. Insulin - acts through IGF – I and promotes hair growth. Cortisol - enhances proliferative actions of IGF – I Shaving has no effect on the rate of hair growth.
  36. 36. DURING PREGNANCY Increase in proportion of follicles in anagen. Reduction in hair density. Post partum - large number of follicles enter into telogen, leading to increased shedding - Postpartum telogen effluvium
  37. 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 dermal papilla and ORS. Insulin acts through IGF – 1 and promote hair growth.
  38. 38. CATAGEN It is marked by down regulation of IGF – 1 receptors and HGF expression in hair bulb. TGF – β, IL – α1, TNF – α are the mediators of catagen activation. Stress, trauma, dexamethasone, ACTH, es tradiol also initiate catagen phase.
  39. 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. 40. COMMON CAUSES OF HAIRFALL Androgenetic Alopecia Alopecia areata Infection Postpartum Hypothyroidism Hyperthyroidism Stress
  41. 41.  Inadequate diet Low serum iron Major surgery / chronic illness Fungal infection of scalp Trichotillomania Oral contraceptives Chemotherapy Other drugs – Vit. A, β blockers, Antidepressants, Anticoagulants, etc.
  42. 42. CAUSES OF HYERTRICHOSIS Hypertrichosis lanuginosa Naevoid hypertrichosis Hypo/hyperthyroidism Anorexia nervosa Dermatomyositis Epidermolysis bullosa Porphyria Drugs – Systemic steroid, minoxidil, psoralen, diazoxide, cyclo
  43. 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.
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