Basic Skin Structure

Basic Skin Structure
Prepared By
RASHIDUL HASAN ROBEL
B. PHARM (RU), M. PHARM (RU)
REG. NO. A4968
PGD-HRM (BIM)
EMBA (ULAB)

1. BASIC SKIN STRUCTURE PREPARED BY RASHIDUL HASAN ROBEL B. PHARM ( RU ) , M. PHARM ( RU ) REG. NO. A4968 PGD-HRM ( BIM ) EMBA ( ULAB )

2. INTEGUMENTARY SYSTEM In biology, integument is the natural covering of an organism or an organ, such as its skin, husk or shell. It derives from integumentum , which means ‘a covering’ in Latin and is an alternative name of skin. The integumentary system is an organ system consisting of the skin , hair , nails , and exocrine glands . Dermatology is the branch of medicine dealing with the skin, nails, hair and its diseases.

3. SKIN Largest organ of the body Completely covers the body Average thickness: 1-2 mm. ( 0.5mm eyelids, 6mm palms and soles) pH: 4 - 5.6 Renewal of skin takes place in 28-50 days by shedding of the outer layer . The thin layer of tissue forming the natural outer covering of the body of a person or animal . Skin is an organ because it consists of different tissues that are joined to perform a specific function.

4. FUNCTIONS OF SKIN 1. Protection - Physical barrier that protects underlying tissues from injury, UV light and bacterial invasion. - Mechanical barrier is part non specific immunity (skin, tears and saliva). 2. Regulation of Body T emperature - H igh temperature or strenuous exercise; sweat is evaporated from the skin surface to cool it down . - vasodilation (increases blood flow) and vasoconstriction (decrease in blood flow) regulates body temperature.

5. 3. Sensation - N erve endings and receptor cells that detect stimuli to temperature, pain, pressure and touch . 4. Excretion - S weat removes water and small amounts of salt, uric acid and ammonia from the body surface 5. Blood Reservoir - D ermis houses an extensive network of blood vessels carrying 8-10% of total blood flow in a resting adult. 6. Synthesis of Vitamin D ( cholecalciferol ) - UV rays in sunlight stimulate the production of Vit -D . Enzymes in the kidney and liver modify and convert to final form; calcitriol (most active form of Vit -D .) Calcitriol aids in absorption of calcium from foods and is considered a hormone .

6. SKIN STRUCTURE 3 layers of skin structure Epidermis Epithelial tissue Dermis Dense connective tissue proper ( irregular) Hypodermis Subcutaneous tissue (loose connective tissue proper and adipose tissue)

7. 3 LAYERS OF SKIN

8. EPIDERMIS Epidermis It i s avascular stratified squamous epithelium  N utrients and oxygen diffuse from capillaries in the dermis Cells of Epidermis Keratinocytes (90 %) : W aterproofs & protects skin, nails, hair, stratum corneum and also provides rigidity by producing tough, triple-helix-shaped protein strand called Keratin . Melanocytes (8 %) : Produce melanin that gives skin color Merkel Cells : Slowly adapting mechanoreceptors that mediate the senses of touch and hair movement . Langerhans ’ Cells : I mmunological defense

9. EPIDERMIS The structural relationship and interface between the epidermis and underlying dermis. The proportions of the various layers differ with the location sampled. Dermis Epidermis Epidermal ridge Dermal papilla

10. SKIN STRUCTURE: EPIDERMIS Thin Skin  Covers most of the body  Has four layers of keratinocytes Thick Skin  Covers the palms of the hands and soles of the feet  Has five layers of keratinocytes

11. SKIN STRUCTURE: EPIDERMIS  The five strata of keratinocytes in thick skin  From basal lamina to free surface Stratum Basale Stratum Spinosum Stratum Granulosum Stratum L ucidum (absent in thin skin) Stratum Corneum

12. Thick skin EPIDERMIS LAYER

13. SKIN STRUCTURE: EPIDERMIS Stratum Basale  It i s attached to basement membrane by hemidesmosomes  Forms a strong bond between epidermis and dermis  Forms epidermal ridges (e.g., fingerprints )  Dermal papillae (tiny mounds) Increase the area of basement membrane Strengthen attachment between epidermis and dermis  Has many basal cells or germinative cells .

14. Thick skin SEM  25 Epidermal ridge Pores of sweat gland ducts Epidermal ridges

15. SKIN STRUCTURE: EPIDERMIS Stratum Spinosum the ‘spiny layer’ Produced by division of stratum basale  8-10 layers of keratinocytes bound by desmosomes  Cells shrink until cytoskeletons stick out (spiny)  Continue to divide, increasing thickness of epithelium  Contain dendritic (Langerhans) cells , active in immune response

16. SKIN STRUCTURE: EPIDERMIS Stratum Granulosum The ‘ grainular layer’ Stops dividing, starts producing keratin & keratohyalin Keratin A tough, fibrous protein Makes up hair and nails Keratohyalin Dense granules Cross-link keratin fibers

17. SKIN STRUCTURE: EPIDERMIS Stratum Lucidum The ‘clear layer’ Found only in thick skin Covers stratum granulosum Stratum Corneum The ‘horn layer’ Exposed surface of skin 15 to 30 layers of keratinized cells Water resistant Shed and replaced every 2 weeks

18. Located between epidermis and subcutaneous layer Anchors epidermal accessory structures (hair follicles, sweat glands) Two components Outer papillary layer Deep reticular layer SKIN STRUCTURE: DERMIS DERMIS

19. SKIN STRUCTURE: DERMIS Papillary Layer  Consists of areolar tissue  Contains smaller capillaries, lymphatics, and sensory neurons  Has dermal papillae projecting between epidermal ridges Reticular Layer  Consists of dense irregular connective tissue  Contains larger blood vessels, lymphatic vessels, and nerve fibers  Contains collagen and elastic fibers

20. Hair Papillary layer Reticular layer Cutaneous plexus Papillary plexus Epidermal ridges Dermal papillae Capillary loop of papillary plexus DERMIS LAYER

21. SKIN STRUCTURE: HYPODERMIS Hypodermis (Subcutaneous Layer)  Lies below the integument  Stabilizes the skin  Allows separate movement  Made of elastic areolar and adipose tissues  Connected to the reticular layer of integument by connective tissue fibers Deposits of Subcutaneous Fat  Distribution patterns determined by hormones  Reduced by cosmetic liposuction ( lipoplasty )

22. SKIN STRUCTURE: HYPODERMIS

23. SKIN APPENDAGES ● HAIR ● NAILS ● GLANDS

24. HAIR Mainly composed of keratin. Dead keratinocytes fuse together to form the hair. At the base of the follicle is the bulb, which contains cells that give rise to the keratinocytes that make up the hair, as well as blood vessels that nourish the growing hair. Each hair follicle also contains arrector pili , a muscle that contracts in response to cold, fright, and other emotions. When the muscle contracts, it pulls the hair in the follicle into a vertical position. Dermis Hypodermis

25. This response may help some mammals keep warm or look bigger to frighten or intimidate their enemies. But in humans, because of our sparse coat of body hair, it merely produces ‘goose bumps’.

26. STRUCTURE OF HAIR Hair Follicle  Hair follicles are the organs that form the hairs  Located deep in dermis  Produces nonliving hairs  Wrapped in a dense connective tissue sheath  Base is surrounded by sensory nerves ( root hair plexus )  Control bacteria

27. Exposed shaft of hair Sebaceous gland Arrector pili muscle Connective tissue sheath Root hair plexus Arrector pili Involuntary smooth muscle Causes hairs to stand up Produces ‘goose bumps’ Sebaceous glands Lubricate the hair STRUCTURE OF HAIR

28. Regions of Hair Hair root Lower part of the hair Attached to the integument Hair shaft Upper part of the hair Not attached to the integument Boundary between hair shaft and hair root Hair shaft Sebaceous gland Arrector pili muscle Hair root Connective tissue sheath Hair bulb Hair matrix Hair papilla STRUCTURE OF HAIR

29. Hair Shaft Structure Medulla Core, dead cells contain soft keratin and air to provide flexibility Cortex Middle layer, dead cells contain hard keratin to provide stiffness Cuticle Outermost, overlapping dead keratinized cells form shiny surface STRUCTURE OF HAIR

30. Hair on Head UV protection Cushion from trauma Insulation Nostrils, Ear canals, Eyelashes Prevent entry of foreign material Body Hair S ensory detection Root H air P lexus Sensory nerves at base of hair follicle that detect slight movement of hair Arrector Pili M uscle Attached to every hair follicle Contract to stand hair perpendicular to skin surface FUNCTIONS OF HAIR

31. STRUCTURE & FUNCTION OF NAIL Nails Protect fingers and toes Made of dead cells packed with keratin Metabolic disorders can change nail structure Nail Production Occurs in a deep epidermal fold near the bone called the nail root Free edge of Nail Body of Nail Laternal Nail fold Lunula Eponychium (cuticle)

32. STRUCTURE & FUNCTION OF NAIL Nail Structure Nail body The visible portion of the nail Covers the nail bed Lunula The pale crescent at the base of the nail Nails Sides Lie in lateral nail grooves Surrounded by lateral nail folds

33. NAIL STRUCTURE C ross-sectional view Lateral nail fold Nail body Lateral nail groove Nail bed Phalanx (bone of fingertip)

34. NAIL STRUCTURE L ongitudinal section Eponychium Proximal nail fold Nail root Lunula Nail body Epidermis Dermis Phalanx Hyponychium

35. SKIN GLANDS An adult human has between 1.6 to 4 million sudoriferous glands, or sweat glands. Most common type called E ccrine S weat G lands , which are found almost all over the surface of the body and are most numerous on the palms and soles. These glands begin deep in the dermis and connect to the surface of the skin by a coiled duct. In addition, nerve fibers that encircle the sweat glands stimulate the glands in response to fear, excitement, or anxiety. Sweat Glands

36. Other sweat glands, known as A pocrine S weat G lands , are much less numerous than eccrine sweat glands. They are also anchored deep in the dermis, but open into hair follicles rather than onto the surface of the skin . Apocrine sweat glands are located mainly in the armpit, genital area, and around the nipples of the breasts.

37. Oil or sebaceous glands are found all over the body except on the palms, the soles, and the top of the feet. These are most numerous on the face and scalp. Most sebaceous glands open into hair follicles. B ut the glands also occur in some hairless areas, such as the lips and inside the mouth. It produces an oily substance called Sebum , which keeps the skin and hair from drying out and inhibits the growth of certain harmful bacteria. Oil Glands

38. Wax or ceruminous glands are located in the ear canal. They secrete a waxy substance that helps prevent foreign particles from entering the ear. These glands are modified sweat glands . Wax Glands

39. SKIN COLOR (Sub-Saharan African, Indian, Southern European, and Northwest European) Skin Color Reason: Melanin, Carotene & Hemoglobin Melanin Pigments Eumelanin Pheomelanin High Eumelanin & Low Pheomelanin - D arker skin and hair color Low Eumelanin & High Pheomelanin - Lighter skin and hair color

40. YOUNG SKIN VS AGED SKIN The deepest layer of the epidermis ‘stratum basale ’ is mostly comprised of keratinocytes and is responsible for renewing the skin every month during young. The movement of skin cells from the basale layer up to top stratum corneum layer takes about 28 days, so your skin cells replace themselves monthly. As you age, skin cell turnover slows. As a result, dead skin cells build up on the skin’s surface, making skin look duller.

41. When you age, collagen production decreases and your skin’s ability to repair collagen and elastin decreases, resulting in wrinkles and loss of elasticity. Young skin has thick bundles of tightly packed collagen while older skin has thin, loose bundles of collagen. YOUNG SKIN VS AGED SKIN

42. As you get older, there’s decreased blood flow through the dermal capillaries. Fewer nutrients reach the epidermis, leading to thinning of the epidermis, slower cell turnover rate and a reduction in the barrier function of the epidermis. These changes lead to increased water loss and dry skin. Skin cells have 30 percent less natural moisture. YOUNG SKIN VS AGED SKIN

43. Hydration Elasticity Firmness Smoothness Healthy Skin Color Dehydration Wrinkles Lack of Collagen Age Spot Pale Skin Color YOUNG SKIN VS AGED SKIN