Basic Anatomy and Physiology of The Skin PDF

Lecture 1 Basic Anatomy and Physiology of The Skin dermatological examination DR : Hanaa Haydar Introduction : What's the dermatology ? Dermatology is the branch of medicine dealing with the skin, and its related diseases. The skin is the largest organ of the body, accounting about 15% of the...

Lecture 1 Basic Anatomy and Physiology of The Skin dermatological examination DR : Hanaa Haydar Introduction : What's the dermatology ? Dermatology is the branch of medicine dealing with the skin, and its related diseases. The skin is the largest organ of the body, accounting about 15% of the total adult body weight and its about ( 4 kg) It performs many vital functions , including protection against external physical, chemical, and biologic assailants, as well as prevention of excess water loss from the body and a role in thermoregulation. The skin has 3 layers 1. epidermis. 2. dermis. 3. Hypodermis. Layers of the epidermis: From the deepest to the most superficial, the epidermal layers are the  stratum basale  stratum spinosum  stratum granulosum  stratum lucidum  stratum corneum.  Layers of the epidermis: The stratum basale : also known as stratum germinativum(single layer), is separated from the dermis by the basement membrane (basal lamina) and attached to it by hemidesmosomes. The cells are columnar, mitotically active stem cells that constantly produce keratinocytes. This layer also contains melanocytes. The stratum spinosum : comprising 8 to 10 cell, is also called the prickle cell layer. This layer contains irregular, polyhedral cells with cytoplasmic processes, sometimes called spines, that extend outward and contact neighboring cells by desmosomes. Dendritic cells can be found in this layer Con-Layers of the epidermis : The stratum granulosum : has 3 to 5 cell layers and contains diamond-shaped cells with keratohyalin and lamellar granules. Keratohyalin granules contain keratin precursors that aggregate, cross-link, and form bundles. The lamellar granules contain the glycolipids secreted to the cell surfaces, functioning as an adhesive to maintain cellular cohesion. The stratum lucidum : comprises 2 to 3 cell layers and is present in thicker skin on the palms and soles. This thin and clear layer consists of eleidin, a transformation product of keratohyalin. Con-Layers of the epidermis : The stratum corneum has 20 to 30 cell layers and occupies the uppermost epidermal layer. The stratum corneum is composed of keratin and dead keratinocytes (anucleate squamous cells) that form horny scales. dead keratinocytes release defensins within this layer, which are part of our first line of immune defense mechanisms. Cells of the epidermis: Cells of the epidermis The epidermal cells include :  keratinocytes. Melanocytes.  Langerhans.  Merkel cells. Cells of the epidermis: Keratinocytes : are the predominant cells of the epidermis(90%) originating from the basal layer. These cells produce keratin and lipids essential for forming the epidermal water barrier. Keratinocytes also contribute to calcium regulation by enabling UVB light absorption in the skin, which is critical for vitamin D activation. Cells of the epidermis:  Melanocyte is a dendritic, pigment-synthesizing cell derived from the neural crest and confined in the skin predominantly to the basal layer. Melanocytes are responsible for the production of the pigment melanin and its transfer to keratinocytes. Melanin is produced in a rounded, membrane-bound organelle known as the melanosome. Cells of the epidermis: Langerhans cells are dendritic cells that act as the skin's first-line cellular immune defenders and are crucial for antigen presentation. These cells contain Birbeck granules and tennis racket- shaped cytoplasmic organelles. Langerhans cells express major histocompatibility complex (MHC) I and MHC II molecules, uptake antigens in the skin, and transport them to the lymph nodes. Cells of the epidermis: Merkel cells are oval-shaped modified epidermal cells found in the stratum basale. These cells serve as mechanoreceptors for light touch and are found in the palms, soles, and oral and genital mucosa, with the highest concentration in the fingertips. The cell membranes of Merkel cells interact with free nerve endings in the skin.  Dermo - Epidermal Junction The interface between the epidermis and dermis is formed by a porous basement membrane zone that allows the exchange of cells and fluid and holds the two layers together. Basal keratinocytes are the most important components of structures of the dermal-epidermal junction. The dermal-epidermal junction composed of four component areas 1- The basal cell plasma membrane with its specialized attachment devices or hemedismosomes 2-lamina lucida 3- lamina densa 4-lamina fibroreticularis { ancoring fibirils } Functions of Dermo - Epidermal Junction The junction serves as the following functions 1- epidermal-dermal adherence 2- mechanical support for the epidermis 3- a barrier to exchange of cell and of some large molecules across the junctions. Dermo epidermal junction Dermis The dermis consists of 2 connective tissue layers=- 1- papillary layer is the upper dermal layer, which is thinner and composed of connective loose tissue that contacts the epidermis. 2 reticular layer is the deeper layer, which is thicker and less cellular. This layer consists of dense connective tissue composed of collagen fiber bundles. The dermis houses the sweat glands, hair, hair follicles, muscles, sensory neurons, and blood vessels. Cell types fibroblast macrophages mast cells and white blood cell Hypodermis The hypodermis, also known as the subcutaneous fascia, is located beneath the dermis. This layer is the deepest skin layer and contains adipose lobules, sensory neurons, blood vessels, and scanty skin appendages, such as hair follicles. HISTORY TAKING Attitude before starting the history - Greet the patient - Introduce your self - Ask for permission # Personal data - Name - Age - Sex - Occupation - Residence - Marital status, and Origin  # Complaint : ( use the patient's own words ) Symptoms : symptomatic or a symptomatic Name of the lesion : Site of the lesion : Duration : Eg itchy pimples and bumps on both legs for one month.  # History of present illness (HPI) * Fitzpatrick seven questions 1- when ? & the onset ( suddenly or gradually ) 2- where ? ( site and where lesions were first noted ) 3- analysis of the symptoms. 4- evolution of the disease. 5- evolution of the single lesion. 6- Aggravating & relieving ( alleviating ) factors. 7- medications.  #_Systemic review #_Past history Past dermatological history Past medical history #_Family history #_Drugs history #_Social history Dermatological examination Skin lesions 1- primary skin lesions 2- secondary skin lesions 3- special skin lesions  skin lesions : --Solid lesions :- papules, plaques and nodules -- flat lesions :- discoloration ( macules and patches ) -- fluid filled :- vesicles, bullae and pustules  SKIN LESIONS PRIMARY SKIN LESIONS :- Macule : circumscribed discoloration of the skin that is not elevated or depressed and less than 5 mm (0.5cm) in diameter. Patch : circumscribed discoloration of the skin that is not elevated or depressed and more than 5 mm (0.5cm) in diameter Papule : circumscribed solid elevation of the skin less than 5 mm (0.5cm) in diameter Plaque : plateau like solid elevation of the skin ( or depression eg. Morphea ), which it is width is greater than its height ( may be due to collection of papules and nodules )  Con- PRIMARY SKIN LESIONS Nodule : circumscribed solid elevation of the skin more than 5 mm (0.5cm) in diameter and its greatest portion usually beneath the skin surface. Vesicle : circumscribed elevation of the skin filled with fluid ( fluid filled cavity ) of less than 5 mm (0.5cm) in diameter. Bulla : circumscribed elevation of the skin filled with fluid of more than 5 mm (0.5cm) in diameter Pustule :circumscribed elevation of the skin filled with purulent exudate ( pus filled cavity ) eg pustular psoriasis ( can be secondary lesion in secondary bacterial infection ) Wheal : localized transient erythematous edematous lesion in the skin of different sizes and shapes that usually last less than 24 hours. cyst nodule  SECONDARY SKIN LESIONS : Scar :a dense plate of fibrous tissues replaces the normal epithelial tissues. Atrophy : thinning of the epidermis , dermis or both. Erosion : oozy partial or complete loss of epidermis ( healing without scar formation ). Ulcer : oozy complete loss of epidermis and at least part of the dermis ( healing by scar formation ). Crust : dried exudate ( serum , pus , blood or combination ). Scale :- visible peeling or flacking of outer skin layers. Fissure : deep vertical splitting of the skin ( or linear cleavage of the epidermis extending to the dermis ) Lichenification : exaggerated skin markings ( resemble the barck tree) thickening and hyperpigmentation with an increase of the surface skin marking scratch. Excoriation : scratch mark. Cyst : a closed cavity or sac containing fluid or semisolid material. The cyst may have endothelial or epithelial lining.  SPECIAL SKIN LESIONS Comedone : plug of keratin and sebum on the orifice of the dilated pilosebaceous unit ( cornification ) Dandruff : visible desquamation from the scalp surface. Burrow : small thin thread like linear or serpiginous tunnel in the skin that housing the female mite sarcobetes scabei caused by the movement of the parasite inside the stratum corneum Ecchymosis : discoloration of the skin resulting from bleeding underneath the dermis may be large area or wide ( extravasation ) Petechia : is small lesion < 4 mm red or purple spot on the skin caused by minor bleeding from broken capillary blood vessels ( extravasation ) Purpura : is a condition of red or purple discolored spots on the skin bw 4 to 10 mm that do not blanch on applying pressure ( extravasation ). Telangiectasia : dilatation of superficial blood vessels.  We have to start by four point of the attitude :- - Greet the patient - Introduce your self - Ask for permission General examination What does Patient look ? Pale , cyanosed or jaundiced Vital signs – pulse, RR, BP and temp Examine LN all groups Palpate for lower limbs edema  Dermatological examination :- - Examination of the lesions - Examination of special sites - Elicit any signs related to the disease  Examination of the lesions : 1. The name of the lesion (macules , patches , papules ,…act). 2. The site of the lesion (face , trunk, extremities). 3. The morphology of the lesion (color, shape , surface , size, margin(well defined border or ill defined border )). surface can be (dome shape , flat topped , smooth, rough or verrucous surface). 4. The pattern of the distribution (linear , annular , dermatomal, grouped , Christmas tree or without specific pattern of distribution ). Annular linear Examination of special sites : Scalp , palms , soles and mucous membranes ( eyes – nose and genitalia ). Elicit any signs related to the disease thanks