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Introduction to Dermatology Part 1&2 (Skin
Structure & Dermatological Language)
Course Objectives:
Below is a summary of the key objectives of the course.
- To understand the basics of skin anatomy.
- To be familiar with the language of dermatology by learning the primary and secondary skin lesions and to be able to describe various skin conditions.
- To enable medical students to recognize the most common skin diseases and to manage them.
- To be familiar with the diagnostic laboratory tests pertinent to dermatology.
- To help students to formulate decent differential diagnoses of skin diseases.
- To gain an overview of the skin manifestations of systemic diseases.
- To be able to deal very appropriately with different emergencies in dermatologic diseases
Done by team leader: عبدهللا الناص
members: ، صقر التميمي عبدالكريم المهيدلي
Revised by: مؤيد اليوسف
Before you start.. CHECK THE EDITING FILE Sources : doctor’s slides and notes + FITZPATRICK color atlas + 435 team [ Color index: Important|doctor notes|Extra]
The Skin:
● The human skin is the outer covering of the body. The skin is a complex, dynamic organ and it is the largest organ of the body. It has a body surface area of 1.5 – 2 m^2 and it contributes to 1/6 to 1/7 of body weight.
Skin function:
● Barrier to harmful exogenous substance & pathogens. ● Prevents loss of water & proteins. (metabolic & endocrine function) ● Sensory organ protects against physical injury. ● Regulates body temperature (Thermal regulation through the sweat glands, constriction or dilation of blood vessels) ● Important component of the immune system. ● Vit.D production by absorbing UVB. ● Has psychological and cosmetic importance such as hair, nails.
The Skin structure consists of:
- Epidermis
- Basement membrane
- Dermis
- Subcutaneous tissue
- Skin appendage. 1) The epidermis: Is the outermost layer of the skin. The main cell types which make up the epidermis are: 1 - Keratinocytes 90% of epidermis + produce keratin the main cell type in the skin 2 - Melanocytes produce melanin responsible for skin color and protection against UV light. 3 - Merkel cells serve a neurological function They are is essential for light touch. 4 - Langerhans cells are antigen presenting cells (immune system). Cornification (keratinization): ● It is the cytoplasmic events that occur in the cytoplasm of epidermal keratinocytes during their terminal differentiation into dead horny cell (corneocyte). The total process takes approximately 2 months ● It involves the formation of keratin polypeptides. ● Abnormalities in this process lead to roughness and scaling of the skin like PSORIASIS (In psoriasis it takes 3 days which will result in a lot of scales) The Epidermal Zones:
- Stratum corneum (cornified layer horny cell layer): is the outermost layer of the epidermis (dead cells with no organelles, the cells in this layer have No nucleus =(corneocytes). Its 25 - cell layer. The cells have a thick envelope that helps it resist external chemicals. In psoriasis you see a nucleus in the stratum corneum, this is NOT normal! (Parakeratosis)
2) Basement Membrane:
- It is a pink undulated homogenous area between the epidermis and dermis
- It consists of number of proteins.
- It is the site of attack injury in blistering diseases.
- Formed by:
- Plasma membrane of basal cells and hemidesmosomes.
- Thin clear amorphous space (lamina lucida).
- An electron dense area (lamina densa).
- **Anchoring fibrils that anchors the epidermis to dermis.
- Dermis:**
- Upper layer is called papillary dermis
- The lower part is called reticular dermis. “Bigger part” Consists of:
- Collagen fibers (strength): Thin fibers in papillary dermis but thick and coarse in the reticular dermis.
- Elastic fibers (elasticity). Protects against shearing forces collagen and elastin are reduced with age, this is why we give collagen for age related wrinkles.
- Ground substance (softness) binds water and maintains skin turgor. proteoglycans
- Fibroblasts (produce collagen)
- Blood vessels (It provides nourishment to the epidermis and interact with it during wound repair, nerves, lymphatics and muscles) So, the function of dermis is to give the skin its strength and elasticity and to provide the epidermis with nourishment The cells in the dermis include: macrophages, fibroblasts, dermal dendritic cells and mast cells (immune functions). 3) Subcutaneous fat: ● Lies below the dermis. Composed of Lipocytes. What is the fundamental unit of Subcutaneous fat? lipocytes. ● Attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. ● The main cell types are fibroblasts, macrophages and adipocytes 5) Skin appendage: are skin-associated structures that serve a particular function It includes: 1 - Eccrine/apocrine glands. 2 - Hair follicles. 3 - Sebaceous glands. 4 - Nail.
Eccrine glands:
- Tubular structures open freely on the skin, not attached to hair follicles. While apocrine is attached to hair follicles.
- Under the influence of cholinergic stimuli. parasympathetic
- Present everywhere except:
- The vermilion borders.
- Nailbeds.
- glans penis.
- Labiaminora.
- Abundant in palms and soles. Apocrine glands:
- Secrete viscous material that gives musky odor when acted upon by Bacteria.
- Presentin: The axillae, Anogenital area, Modified glands in the external ear canal, The eyelids (moll’s glands) andareolae.
- Under adrenergic stimuli. Sebaceous glands:
- Attached to hair follicles or open freely. If attached, it’s called pilosebaceous unit.
- Present in the scalp, forehead, face and upper chest except palms and soles.
- Secrete sebum to moisturize the skin.
- Sebaceous glands are under the control of androgens
- SG in the areola are called Montgomery tubercles , in the eye they are called meibomian glands. Ectopic glands in the mucous membrane are called → Fordyce spots Hair follicles:
- Hair follicle has the hair shaft, hair bulb and the bulge.
- Pilosebaceous unit include: hair follicle + sebaceous gland+ arrector pili muscle. Nails:
- The nail plate is formed of hard keratin.
- Proximal nail fold morphology can be altered in connective tissue disease.
- The lunula is the visible part of the matrix.
- The matrix covers the mid-portion of the distal Phalanx.
- Fingernails grow 3mm/month. Toenails grow 1mm/month.
- Nails can be affected in systemic and skin diseases. The doctor focus on 2,3 in the picture and other disorders that related to skin diseases.
Generalized Localized
- Symmetrical: either universal or bilateral in the same regions, the left side is affected in a similar way to the right side.
- Asymmetrical: either diffuse or unilateral Wholly or predominantly on one side of the affected region Acral peripheral body parts e.g. vitiligo Dermatomal following the dermatomes, e.g. Shingle Malar malar bone (cheeks). Sun exposed areas Trauma sites Extensors ex: extensor surfaces of the UL Flexures Specific part
◆ Terms Used in Dermatology:
◆ Skin lesions: skin lesions are divided into primary & secondary lesions
1) Primary lesions= basic lesions: ● Macule/patch ● Papule/plaque ● Nodule ● Cyst ● Wheal ● Vesicle/bulla ● Pustule ● Purpura ● Telangiectasia ● Tumor
**Primary skin lesion Description Picture
- Macule** a flat circumscribed area of altered skin color less than 1 cm in size. It Lacks surface elevation or depression. (not palpable) e.g. freckle, vitiligo. 2) Patch (^) Flat circumscribed skin discoloration; More than 1 Cm it Lacks surface elevation or depression ). e.g Vitiligo, melasma. 3) Papule (^) A papule is a superficial, elevated, solid lesion, generally considered <0.5 cm in diameter. 4) Plaque A flat-topped palpable lesion more than 0.5 cm in size. Confluence (group) of papules leads to the development of larger, usually flat-topped, circumscribed, plateau-like elevations known as Plaques lacks a deep component e.g. Plaque psoriasis 5) Nodule (^) A solid , circumscribed elevation whose greater part lies beneath the skin surface. >0.5 cm in diameter; **with deep component. (elevation+depth)
- Wheal** A transient, edematous slightly raised lesion, characteristically with a pale center and a pink margin. Commonly seen in urticaria اضغط على الصور للحجم الكامل
2) Secondary skin lesions: Lesions that Develop during the evolution of skin disease or created by scratching or infection. ● Scale ● Excoriations ● Fissure ● Erosion ● Ulcer ● Scar ● Lichenification ● Crust ● Atrophy ● Poikiloderma **Secondary skin lesion Description Picture
- Scale** Thickened stratum corneum. 2)Excoriations Linear erosion induced by scratching. 3) Fissure (^) Vertical loss of epidermis and dermis with sharply defined walls, (crack in skin). 4) Erosion (^) A partial focal loss of epidermis that heals without scarring. a moist, circumscribed, usually depressed lesion that results from loss of all or a portion of the epidermis. (433TEAM) 5 ) 5 ) Ulcer (^) A full thickness focal loss of epidermis and dermis; heals with scarring
6) Crust (^) A collection of cellular debris, dried serum and blood. Antecedent primary lesion usually a vesicle, bulla, or pustule. 7) Scar A collection of new connective tissue that May be Hypertrophic or Atrophic. Which Implies dermo-epidermal damage. A permanent lesion that results from the process of repair by replacement with fibrous tissue. Ex: Surgical scar. 8) Lichenification Increased skin markings secondary to scratching. Patches of increased epidermal thickening with accentuation of skin markings and pigmentation. Lichen simplex chronicus. Seen in Eczema 9) Poikiloderma (^) not in the slides. A morphologic descriptive term, refer to the combination of atrophy, telangiectasia, and pigmentary changes (hypo or hyperpigmentation) e.g. Dermatomyositis. 10) Atrophy (^) not in the slides
Koebner’s phenomenon Trauma to the skin reproduce certain diseases like Psoriasis, Vitiligo, Lichen planus and Warts these diseases are prone to koebnerization. Video ال لو تعرضوا لجرح أو خبطة، یصیرون معرضین إلن المرض اللي عندهم یمتد لمكان الجرح أو الخبطة. عشان مث ألن ممكن یطلع لهم بهاق فيlaser fractionalیسوونماننصحهم(Vitiligo(المرضى المصابین بالبهاقا كذ الوجه بعد اللیزر (بینما كانت المنطقة سلیمة قبل اللیزر). المصابین بأحد األمراض أعاله نحرص على إننا ننبههم على .لو بیسوون عملیات إمكانیة امتداد المرض للمنطقة المصابة في حال تعرضهم ألي جرح، خصوصا Dermatographism Firm stroking of the skin produces erythema and wheal. Seen in physical urticaria. In patient with atopy, stroking produces white dermatographism rather than red. ◆ Investigations: 1 - Wood’s lamp: Produces long wave UVL (360 nm) Useful in:
- Tinea Versicolor Versicolor-yellowish green fluorescence.
- Tinea Capitis yellow green fluorescence in M. canis, M. andouini.
- Vitiligo (milky white) نفس الصوره االولى
- Erythrasma coral red fluorescence الصوره الثانیهنفس
- Melasma becomes more intensified 2 - KOH preparation (^) • For fungus (used for scaly lesions not vesicular)
- Cleanse skin with alcohol Swab.
- Scrape skin with edge of microscope slide onto a second microscope slide.
- Put on a drop of 10% KOH.
- Apply a cover slip and warm gently.
- Examine with microscope.
3 - Tzanck smear: (^) • (used in vesicular lesions to diagnose):
- Herpes simplex or VZV (multinucleated giant cells)
- Pemphigus Vulgaris (acantholytic cells).
- Stain with Giemsa stain. → Examine under microscope 4 - Prick test: يسوون على اليد
- Primary method for the diagnosis of IgE mediated allergies in most allergic diseases (type 1 hypersensitivity reaction).
- Useful in the diagnosis of hay fever allergy, food allergy, latex allergy, drug allergy and bee and wasp venom allergy.
- Put a drop of allergen containing solution.
- A non bleeding prick is made through the drop
- After 15-20 min the antigen is washed , the reaction is recorded
- Positive test shows urticarial reaction at site of prick.
- Emergency therapeutic measures should be available in case of anaphylaxis. 5 - Patch skin test يسوونه على الظهر
- Important in Allergic contact dermatitis. (Type 4 cellular immunity)
- Select the most probable substance causing dermatitis.
- Apply the test material over the back.
- Read after 48 & 72 hr.
- Positive patch test showing erythema and edema.
- In severe positive reaction vesicles may be seen. 6 - Skin punch biopsy • Clean skin with alcohol.
- Infiltrate with 1-2% xylocaine with adrenaline.
- Rotate 2-6 mm diameter punch into the lesions.
- Lift specimen and cut at base of lesion.
- Fix in 10% formalin
- For Immunoflourescence put in normal saline.
- Suture if 4 or 5 mm is used. 7 - Direct immunofluorescence:
- Used to diagnose autoimmune diseases e.g. Pemphigus Vulgaris, Bullous pemphigoid.
- Detects immunoglobulin and complement deposits in skin.
- The deposits will give a green fluorescence
- Fluorescence will be noted if immunoglobulin deposits are found intercellular between the epidermal cells as in pemphigus vulgaris, while found the Basement membrane zone as in bullous pemphigoid.
