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SKIN AND ITS APPENDAGES.pptx
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- 2. SKIN Skin is theouter covering of the body which is in contact with the external environment Functions • Protection of underlying structures • Excretion of salts & metabolites like urea • Sensation • Secretion of sweat & sebum • Regulation of body temperature • Synthesis of Vitamin D by action of UV rays of sun
- 4. Epidermis It is themost superficial layer of the skin, composed of stratified epithelium. There is no blood vessels or nerve endings in the epidermis. Colour of skin is affected by 3 main factors: • Melanin, dark pigment secreted by melanocytes. It protects the skin from harmful effects of sunlight. • Level of oxygenation of hemoglobin • Bile pigments in blood & carotene in subcutaneous fat which give skin the yellow colour.
- 6. 5 l ay e r s o f e p i d e r m i s 1. Stratum basale (deep) 2. Stratum spinosum (Malpighian layer) 3. Stratum Granulosum m 4. Stratum Lucidum 5. Stratum Corneum (Superficial)
- 7. S t ra t u m Basale • Deepest • Double layered arrangement of cells • Cells multiply in this layer also known as Germinal layer/ Stratum Germinativum • This layer is rich in melanin pigments
- 8. Stratum spinosum • Severallayers of polygonal keratinocytes • Cells are attached to one another by numerous Desmosomes • Germinative zone
- 9. Stratum Granulosum • Few(1-5) layers of flattened cells • Cytoplasm contain granular material
- 10. Stratum Lucidum • Lucidmeans Clear. Here the cytoplasm of the cells is clear and contain few nuclei in them
- 11. Stratum Corneum • Superficiallayer • Made up of flattened scale like cells which are constantly replaced. Containing a protein called KERATIN • Resistant to permeability • The thickness of this layer is greatest where the skin is exposed to maximal friction Eg:- Soles and palms • The superficial layer constantly sheds off & replaced by proliferation of cells in deeper layers
- 12. • Dermis istough & elastic. It is the inner layer forms true skin. Composed of collagen fibres interlaced with elastic fibres . • The structures in dermis are • Blood vessels • Lymph vessels • Sensory nerve endings • Sweat glands & their ducts • Hair roots, hair follicles & erector pili muscles • Sebaceous glands Two secretions of skin are Sweat & Sebum DERMIS
- 13. • Hairs • Nails •Sebaceous Glands • Sweat Glands Appendages of the skin
- 15. • Present onthe skin covering almost all parts of the whole body. • Not present : Palms, Soles, Ventral surface & sides of the digits & some parts of the male & female external genitalia
- 16. Hair • Hairs areformed by a down growth of epidermal cells into the dermis or subcutaneous tissue called hair follicles. • At the base of follicle is the hair bulb, the hair is formed by the multiplication of cells of the bulb, and pushed upwards away from source of nutrition, cells die & become keratinised. • Colour of hair is genetically determined & depends on the amount of melanin present.
- 17. Parts of Hair •The visible part – shaft • Embedded part – root • Expanded lower end of the root – bulb • The bulb is generated invaginated from below by part of the dermis – hair papilla • Root is surrounded by a tubular sheath – hair follicle • Hair roots are attached obliquely to the skin.
- 19. Structure of hairshaft Hair – Modified part of stratum corneum Has outer cortex and inner medulla in large hairs, no medulla in thin hairs
- 20. Both in medulla& cortex minute air bubbles are present
- 21. Arrector Pili Muscles •These are bands of smooth muscles attached at one end to the dermis, just below the dermal papilla & at the other end to the connective tissue sheath of the hair follicle
- 22. • Contraction ofarector pilorum muscle results in erection of hair shaft
- 24. • Seen inrelation to the hair follicles. • Found in dermis of the skin. • Gland consists of a number of alveoli which is connected to the ducts, & the Ducts open into the hair follicle • Is a holocrine gland • Sebaceous gland is situated between the hair follicle and the arrector pili muscle. • Secretes sebum - Contains lipids & cholesterol Functions of sebum – Oily in nature, keep skin and hair soft – Prevents dryness of skin – Makes skin resistant to moisture
- 26. Sweat Glands • Foundin deeper parts of the dermis. • It produce sweat or perspiration. • Bodies of glands lie coiled in the subcutaneous tissue. • Some ducts open on to the skin surface & others open into the hair follicles. • Secretion of glands (sweat) has high water content. Evaporation of sweat causes cooling of the body. • Sweat glands are more numerous in the palms of hands & sole of feet.
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- 29. ECCRINE (Atypical)GLANDS • Widelydistributed • Numerous on forehead, scalp, palms & soles • Presents a highly coiled secretory portion called as body within the dermis & a narrower ductal portion, which opens on skin surface • Secretions of sweat glands are clear, colourless and hypotonic
- 30. APOCRINE (Typical)GLANDS • Foundin Axilla, Areola, Perianal region, Prepuce scrotum, Mons pubis etc. These glands secrete a protein rich, milky fluid which is initially odourless but acquires a distinct odour due to bacterial decomposition
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- 32. • Nails areplates of keratinised epithelial cells • They form a protective covering on the dorsal surface of fingers & toes. • Consists of 3 parts – Proximal part or root – it is implanted into a groove on the skin. – Exposed part or body – Free distal border • The root of nail is covered by Cuticle. • And forms the hemispherical pale area called lanula.
- 33. • The tissueon which the nail rest is the nail bed which is composed of stratum basale & stratum spinosum, highly vascular which gives nail a pink colour.
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