The document provides information about human skin anatomy, organization, histology, function and diagnosis. It discusses the key components and layers of the skin including the epidermis, dermis and skin appendages. The epidermis is composed of the basal, spinous, granular and stratum corneum layers. The dermis contains collagen, elastic and ground substance fibers. The skin has important protective, sensory and temperature regulating functions. Common skin lesions and their characteristics are also defined.

1. Anatomy, Organization, Histology, Function of Human Skin and Diagnosis By: Dr. Kazhan Ali Taufiq Kadir October 2010

2. The skin: is theinterface (surface)between human & environment is one of the largest organs in the body Its surface area is of 1.8 - 2 m2 & makes up approximately 16% of our body weight ≈ 4kg is a window through which the physician can "see" the entire body

3. Normal Human Skin

4. Normal Skin Low Power with Labels

6. No blood vessels

7. Keratinocytes make 85% of it, other cells are melanocytes, langerhans cells, merkel cells

11. Functions of the Skin barrier to physical agents protects against mechanical injury prevents dehydration of body through fluid loss reduces the penetration of UV Radiation helps to regulate body temperature provides a surface for grip acts as a sensory organ acts as an outpost for immune surveillance plays a role in Vitamin D production has a cosmetic association

12. Functions of the skin 1. Protection against: chemicals, particles horny layer UV radiation melanocytes Antigens, haptens langerhans cells Microbes langerhans cells 2. Preservation of horny layer balanced internal Environment 3. Prevents loss of horny layer water, electrolytes, macromolecules

13. 4. Shock absorber, dermis & subcut. fat Strong, elastic, compliant 5. Tempratureblood vessels Regulation eccrine sweat glands 6. Insulation subcutaneous fat 7. Sensation specialized nerve endings 8. Lubrication sebaceous glands 9. Protection & prisingnails 10. Calorie reserve subcut. Fat 11. Vitamine D synthesis keratinocytes 12. Body odor & apocrinesweat glands pheromones: (chemicals for communication) 13. psychological: skin, lip, hair & nails display

14. Based on the thickness of the epidermis, skin can also be classified as thick or thin: 1) Thick skin - covers palms and soles, - has sweat glands, but lacks hair follicles, arrectorpili muscles, and sebaceous glands 2) Thin skin - covers most of the rest of the body - contains sweat glands & hair follicles, arrectorpili muscles, and sebaceous glands.

16. single layer of columnar layer

17. Keratinocytes have hemidesmosomes attached them to underlying lamina densa

19. 7-9 layers of cells

20. Keratinocytes firmly attached by cytoplasmic process (desmosomes) & intercellular glycoprotein cement

21. Tonofilaments are small fibers running from cytoplasm to desmosomes

22. Tonofilaments packed into bundles called tonofibrils, more numerous in this layer

23. 3. Granular layer: 2-3 layers Cells flatter than spinous layer, No nucleus No intracytoplasmic organelles More tonofibrils Contain irregular basophilic granules of keratohyalin.

27. Lamina Densa Fine anchoring filaments cross lamina lucida & connect lamina densa to plasma membrane of basal cell layer.

29. Function of DEJ:Provide mechanical support Encouraging adhesion, growth, differentiation & migration of overlying basal cells Act as semipermeable filter that regulate transfer of nutrients & cells between dermis & epidermis

30. Dermis: DermalLayers: 1. Papillary layer 2. Reticular layer Dermal Fibers: 1. Collagen Fibers 2. Elastic (Elastin) Fibers

32. Support epidermis structurally & nutritionally

33. Thickness greatest in palm & soles & least in eyelids & penis

36. elastin is made up of polypeptides rich in glycine, desmosine, valine

38. Functions:

39. Ground substance binds water, allowing nutrients, hormones & waste products to pass through dermis

40. Acts as lubricants between fibers

44. Nerves One million nerve fibers mostly in the face & extremities Cell bodies are in dorsal root ganglia Both mylinated & unmyelinated fibers exist Itch is follow stimulation of free nerve endings close to dermo-epidermal junction

45. Skin appendages (Adnexa): SHANS: 1. Sweat glands 2. Hair 3. Arrector pilli muscle 4. Nails 5. Sebaceous glands

47. Asthmus: between entrance of seb. g to attachment of arrectorpili muscle

48. Hair Matrix: is the inferior portion including the hair bulb

49. Free of hair areas: Lip, glans penis, labia minora, palms, soles

50. Hair cycle:anagen, catagen & telogen

51. Typesof hair: 1- Lanugo hair 2- Vellus hair 3- Terminal hair

52. Nails Hard keratin of nail plate formed in nail matrix which lies in an invagination of epidermis on back of terminal phalanx of digits toes It provide strength & protection for terminal phalanx & allow handling of fine objects Finger nail growth is 0.5-1.2 mm per week Slower in toe nails Faster growth in summer

53. Skin Emberiology: Origins of the Integumentary System: (The Skin) The skin basically consists of two layers that are derived from two germ layers: ectoderm and mesoderm. The epidermis is from surface ectoderm. The dermis is derived from mesoderm. Mesenchyme: is the embryonic meshwork of connective tissue (CT).

54. Hair: A hair follicle develops as a proliferation of the epidermal stratum germinativum and extends into the underlying mesenchyme. Nails:develop from thickened areas of epidermis at the tips of each digit called nail fields. Later these nail fields migrate onto the dorsal surface surrounded laterally and proximally by folds of epidermis called nail folds

55. Both the sebaceous glands and sweat glands (+ mammary glands) are derived from the epidermis and grow downwards into the dermis. The majority of sebaceous glands originate as buds from developing hair follicle root sheath. Sebaceous glands in the glans penis and labia minora (independent of hair follicles) develop similarly, but as buds from the epidermis.

56. Sweat glands: - Eccrine sweat glands located throughout the body originate as downgrowths from the epidermis into the underlying mesenchyme. As a result, these eccrine ducts open onto the surface of the skin. - Apocrine sweat glands are located in the axilla, pubic region, perineal region, and areolae of the nipples. originate instead as downgrowths from the epidermal stratum germinativum (which also gives rise to hair follicles). As a result, these apocrine ducts open into the upper part of hair follicles above sebaceous gland openings.

57. The Physiology of Skin The skin is a metabolically active organ with vital functions such as protection and homeostasis. When discussing the physiology of the skin and its derivatives, the following topics are important:

58. Keratinocyte Maturation: The aging of basal cells into the corneocytes (dead cells) is crucial. The stratum corneum is important in preventing all manner of agents from entering the skin, including micro-organisms, water and particulate matter. It's the epidermis that also prevents loss of vital body fluids. The dividing basal cell on average replicates every 200 to 400 hours, and the resulting cell takes 14 days to differentiate and 14 days to be shed.

59. Hair Growth Unlike most mammals, humans are considered "nude“ رووت ; thus, hair does not play the same vital role of heat conservation. However, the hair on the scalp does protect us from UV radiation and minor injury. Today, hair is of cosmetic value. Hair growth is cyclical and has three phases. The 3 phases are:

61. 1) Anagen is the growing phase. Its duration depends on the location of the hair. For eyebrow hair, this phase only lasts 4 months, but for scalp hair it lasts from 3-7 years. At any moment, 80-90% of scalp hairs are in anagen; daily, approximately 50-100 scalp follicles switch to the catagen phase. 2) Catagen is the resting phase and lasts 3-4 weeks. There is a stop to hair protein synthesis as the hair follicle retreats towards the surface. At any moment, less than 1% of hairs are in the catagen phase. 3) Telogen is the shedding phase and is characterized by hairs with a short club root. Daily, approximately 50-100 scalp hairs are shed. At any moment, 10-20% of scalp hairs are in telogen.

62. Dermatological General & Specific Terms: Dermatologists have some universal terms that are used when describing skin conditions: Lesion: Eruption (or rash): 2 Types of Skin Lesions: 1- Primary Skin Lesions 2- Secondary Skin Lesions

63. 1- Primary Lesions: are the first to appear and are due to the disease or abnormal state. Must be distinguished from secondary or induced lesions Macule Papule Nodule Vesicle Bulla Pustule Cyst Plaque Wheal, Erythema, abscess, Angiodema, Tumor, Petechiae, Purpura, Ecchymosis, Haematoma, Burrow, Comedo, Telangiectasia & Poikiloderma

64. Macule:small,flat, nonpalpable circumscribed area of change in color or texture of the skin. are < 0.5 cm in size, more than 0.5 called patches 1. Macules (individual) may be the result of (A) hyperpigmentation: e.g. brown as inlentigos) (B) depigmentation (e.g. vitiligo), (C) vascular dilation (e.g. erythema) 2. Multiple well-defined macules of various shapes and sizes. In this case, the macules blanch upon pressure(diascopy) and thus are due to inflammatory vasodilation.

65. Papule: small solid elevation of skin < 5 mm in diameter. Projects above the plane of the surrounding skin Flat-topped (in lichen planus) or Dome shaped (in xanthomas) or Spicular (if related to hair follicles)

66. Nodule:palpable, solid, round, or ellipsoidal lesion Its depth of involvement and/or palpability differentiate it from a papule rather than its diameter Larger than papules: > 5 mm diameter (in both depth & width) Any layer of the skin Edematous or solid. 5 types of nodules: epidermal, epidermal-dermal, dermal, dermal-subdermal, and subcutaneous

67. Vesicle (blister):circumscribed, elevated lesion is < 5 mm in diameter containing serous (clear) fluid. A vesicle/bulla is the technical term for blisters Vesicle walls can be so thin that the contained serum, lymph, blood, or extracellular fluid is easily seen. Fluid can be accumulated within or below the epidermis Pustule: Vesicle contains pus Bulla: Vesicle more than 0.5 cm

68. Bulla: A vesicle with a diameter > 5 mm. Subcorneal 2. Epidermal Subepidermal vesicles

69. Pustule:superficial, elevated lesion that contains pus (pus in a blister). may vary in size and shape. The color may appear white, yellow, or greenish-yellow depending on the color of the pus. Pus is composed of leukocytes with or without cellular debris may also contain bacteria or may be sterile 1. A pustule is basically a papule containing pus 2. Superficial, subcorneal pustules ( e.g. pustularpsoriasis) `

71. Wheal: elevated, transitory, compressible papule or plaque produced by dermal edema The papule or plaque is usually rounded or flat-toped, and evanescent, disappearing within hours. The borders of a wheal are sharp, but not stable and can move from involved to adjacent uninvolved areas over hours. The epidermisis not affected. can be pale red or white (especially in the center) if edema is sufficient to compress superficial vessels.

72. Erythema: is redness caused by vascular dilatation

73. Abscess: localized collection of puss more than 1 cm in diameter

74. Angiodema: is diffuse swelling caused by subcutaneous oedema

75. Tumor: is an enlargement of the tissue by normal or pathological material or cell greater than 1 cm in diameter

76. Petechiae: pinhead sized macules of blood

77. Purpura: larger macule or papule of blood

78. Ecchymosis: a collection of blood greater than 1 cm in size outside the vascular tree (extravasation of blood), in the skin and within tissue

79. Haematoma: is swelling from gross bleeding

80. Burrow: is linear or curvilinearpapuleas in scabies

81. Comedo: is a plug of greasy keratin wedged in a dilated pilosebaceous orifice

82. 2- Secondary Lesions From the natural evolution of primary lesions a. From Eroded area left by bursting vesicle or b. From the patient's manipulation of the primary lesion (scratching):- ScaleUlcerCrustErosionExcoriationLichenificationAtrophyScar, fissure, Sinus, Keratosis, Striae& Pigmentation

83. Scale: is a flake is accumulation or abnormal shedding arising from horny layer keratin: (SC) may be primary or secondary. usually indicates inflammatory change and thickening of the epidermis

84. Erosion, Fissure (fish Your), and Ulcer

85. Erosion: moist, circumscribed, usually depressed lesion due to loss of all or part of the epidermis, heals without scardue to: 1. Herpes viruses (vesicles) 2. Pemphigus (bullae) 3. Toxic epidermal necrosis :TEN

86. Ulcer: a "hole in the skin" circumscribed area of skin loss extending through the epidermis and at papillary dermis heals with scarring results from the impairment of vascular and nutrient supply to the skin

89. Lichenification: chronic thickening of the skin along with increased skin markings. Results from scratching or rubbing

90. Atrophy: Thinning of skin caused by diminution of epidermis, dermis or subcut. tissue paper-thin, wrinkled skin with easily visible vessels. Results from loss of epidermis, dermis or both. Seen in: - aged, - some burns, - long-term use of highly potent topical corticosteroids (Cs).

91. Scar:is a pattern of healing where normal structures replaced by fibrousCT at a site of injury to the dermis. 1- HypertrophicScar 2- AtrophicScar 3- Sclerotic or hard Scar due to collagen proliferation

92. 1- Hypertrophic or 2- atrophic scar. 3-Sclerotic or hard Scar

93. Fissure: is a skin slit Heel fissure

94. Sinus: is a cavity or channel permits escape of fluid or pus

95. Keratosis: is a horn like thickening of stratum corneum(SC)

96. Striae:is a streak like linear atrophic pink purple or white lesions (or called stretch marks).

97. Pigmentation:more or less darker than surrounding skin

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