Anatomy and Physiology of the Skin PDF

Anatomy and physiology of The SKIN Special Sense Block Dr.Barzan khalid sharaf M.B,Ch.B,FABMS The skin consists of: 1. Superficial epithelial components- the epidermis- derived from the ectoderm. 2.underlying connective tissue components- the dermis and hypodermi...

Anatomy and physiology of The SKIN Special Sense Block Dr.Barzan khalid sharaf M.B,Ch.B,FABMS The skin consists of: 1. Superficial epithelial components- the epidermis- derived from the ectoderm. 2.underlying connective tissue components- the dermis and hypodermis- which is derived from mesoderm. --In between there is a basement membrane zone. Skin appendages - hair, nail, sweat glands and sebaceous glands- are derived from the epidermis. Epidermis BM oemist hypodermis  n Pat 1containhairroots eatin 31 9  EPIDERMIS Is a cellular avascular tissue. The epidermal thickness is on average about 0.2 mm 95% of the cells are epidermal keratinocytes that proliferate and divide in the epidermal basal layer and move up to the upper layers as theytfinocyteslmelarocytesthh.at mature (to form cornified cells). Types of Epidermal cells: 1. The keratinocytes constitute the keratinizing or malpigian system. 2. The melanocytes constitute the pigmentary or melanocytes system. aPQartioen presenting us 3. The Langerhans cells responsible for the reticuloepithelial or Langerhans's system. 4. The Merkel cell constitute the Merkel system. Go valhapelmechanorecepors es e 1 40  m Bingham come The Epidermal layers 1. STRATUM MALPIGHI: Viable cells which consists of: A. STRATUM BASALE- STRATUM GERMINATIVUM Single basal layer of cubical or columnar cells rest on the basement membrane and is in contact with underlying dermis. Mitosis occur mainly in this layer, serve as source of stem cells for all new keratinocytes. The basal cells have desmosomes (for cell- cell attachment), gap junctions (for cell communication), and basement membrane hemi desmosome (for connection with the extracellular matrix and underlying basal membrane).  B. STRATUM SPINOSUM -PRICKLE CELL LAYER- Several layers of polyhedral cells possessing spines or prickles. The cells are firmly attached to each other by desmosomes. Characteristically there is a network of fibers and filaments that ramify around the nucleus and in the periphery of the cells, they are known as TONOFILAMENTS. E.M. of the desmosomes- inter cellular cement - shows the following components: Tonofibrils. Tonofilaments. Dense plate. Membrane coating granules. Carbohydrate rich intercellular substance. C. STRATUM GRANULOSUM- Granular cell layer- Several layers (2-3 layers) of flattened cells contain conspiculous basophilic keratohyalin granules. Spherical lamellar granules also known as Odland bodies can be observed in the granular cell layers by electron microscopy. The main component of lamellar granules is released into the intercellular space of horny cells as stratum corneum lipid.  2. STRATUM CORNEUM - Horny cells A.STRATUM LUCIDUM - Clear cell layer - Several layers of flattened, a nucleate cells, has hyaline appearance, Varies in thickness in different regions of the body mostly apparent in the palm and sole. B.STRATUM CORNEUM PROPER (10-20 layers) Many layers of very large, flattened, cornfied, a nucleated cells. The cells continuously being shed from the surface and replaced by new keratinocytes from deeper layer. The mean time for the transfer of the keratinocytes from the basal layer to the horny layer has been calculated to be approximately 28 days. It is shorter in the cheek and oral mucosa 3-4 days.  It Form a tough elastic surface of the skin It Form epidermal fluid barrier, preventing inward transfer of substances from the environment and loss of fluid from the body. Keratinization is the process of continuous shedding from the surface and replacement 0 by new cells from the deeper layers Keratin is markedly hydrophilic.  MELANOCYTE Developmentally derived from neural crest ectoderm. Scattered among the keratinocytes throughout the basal layer as well as in hair follicles and dermal connective tissue. They are dendritic cells, each cell is in contact with 36 keratinocytes forming EPIDERMAL MELANIN UNIT. Each melanocyte contains organelles called MELANOSOMES in which melanin pigment manufactured. Melanin is produced by the oxidation of the amino acid tyrosine in the presence of enzyme tyrosinase: Tyrosinase Tyrosine ----- 3,4 Dihydroxyphenylalanine (DOPA) Tyrosinase DOPA --------- Dopamine -------- Melanin. The amount of melanin present depends on the activity of melanocytes and not on their number.  All races have the same number of melanocytes but they differ in the number, size, shape, distribution and degradation of the melanosomes. The whole process of melanin synthesis is under M.S.H. control. The most important role of melanin is protecting the skin from UV rays and preventing the occurrence of malignant tumors and sunlight injury to the skin. The darker the skin of a particular race, the lower is the incidence of skin cancer caused by UV light. Exposure to sunlight darkens the skin. This darkening may occur immediately after exposure and may be temporary, when melanins are oxidized temporarily, or it may occur after several days of exposure, when there is an increase in melanin synthesis and mature melanosome formation. Melanins can also act to absorb harmful active substances, metals and drugs. another LANGERHANS CELLS Dendritic cells among the prickle cells. spinoem 0 Scattered throughout the stratum Malpighi especially Also has been found in the oral mucosa, esophagus, vagina and cervix, as well as in hair follicles, sebaceous glands ducts, apocrine ducts, thymus, lymph nodes and dermal lymphatic vessels. Origin is from the bone marrow Functionally act as antigen presenting cells and thought to form a system of reticuloepithelial cells that are involved in clearing antigen from the skin, traps externally applied allergens , bind and process them then migrate to lymph nodes, where stimulate production of specifically sensitized lymphocytes which is in turn migrate to the epidermis,  MERKEL CELLS TYHpt.in Is a Neural crest derived cells migrate from the dermis into the epidermis during fetal life scattered among the keratinocytes. Involved in a touch reception. Greater numbers of Merkel cells are seen in the fingers, oral mucosa and hair roots. After physical stimulation, neurotransmitters are secreted from Merkel cell granules, and the tactile information is transmitted to the sensory nerve. DERMO-EPIDERMAL JUNCTION E.M. study shows the following structures: 1- Tonofilaments. 2- Attachment plaque. 3- Plasma membrane. 4- Sub- basal dense plaque. 5- Lamina Lucida. 6- Basal lamina. 7- Anchoring fibers. 8- Dermis.  DERMIS In hairfor The dermis is approximately 15 to 40 times as thick as the epidermis and is about 3 mm thickness. It consists almost entirely of a network of fibers support the glands , hair follicles, blood vessels, lymphatics and nerves. Types of fibers: 1.Collagen: most numerous, lie horizontal o to the surface and parallel to the lines of tension (Langers lines) immature collagen fibers known as reticulum.  Superficial papillary and subpapillary layer Composed of fibrous tissue bandles with small amounts of elastic tissue, each papillae contain sensory nerve ending, blood vessels and lymphatics. Inter-papillary spaces are epidermal in origin called RETE RIDGES. Inner or deep reticular layer A network of collagenous bandles and elastic fibers arranged parallel or obliquely. The elastic fibers enblock the sebaceous and sweat glands, hair follicles and erector pili muscles. The cellular element are sparse; the most abundant are fibroblasts, others include melanocytes, macrophages, mast cells, migratory leukocytes and adipocytes.  HYPODERMIS Subcutaneous loose connective tissue act as transitional zone contains fat cells, white and yellow C.T., coils of sweat glands, and roots of some hair. The hypodermis is connected below with underlying deep fascia, aponeurosis, or periosteum. It provides support for the overlying skin and attachment to deeper tissues. Serve as storage depot for fat and contains large blood vessels that supply the skin. I CUTANEOUS APPENDAGES and SECRETORY ORGANS  SWEAT GLANDS A- Eccrine glands Eccrine gland I They have a wide body distribution except at the lips, beneath the nails, and on the glans penis, clitoris, and labia minora; they are most numerous on the palm and soles. i Structurally each gland has a coiled secretory portion located in the dermis and hypodermis, straight dermal duct portion, and spiral epidermal duct part usually open at the apex of epidermal ridges.  They are innervated by sympathetic cholinergic fibers. Those on the palm, axillae, and forehead respond primarily to emotional stimuli. Sweating is intermittent under the control of: 1. Thermoregulatory center in the hypothalamus. 2.Sweating may also initiated locally e.g facial sweating after eating spicy foods- gastatory sweating. 3.Axon-reflex in the region of certain skin lesions Hypoth Etheumonedolly Local  Axon reflex They play important role in temperature regulation. Their secretion is colorless, odorless, hypotonic, composed of 99% by wt of water, also contain Na, K, Cl, urea, lactate, a.ac, 000 calcium and iron in decreasing order. 99 the  Foo B. Apocrine glands Less abundant than the eccrine glands, Found in the axillae, pubis, prepuce, scrotum, periumblical area eye lids and external auditory meatus (Ceruminous glands). Anatomically develop close to the hair follicles and open in the follicle above the opening of the sebaceous duct. The secretion milky, odorless and have sexual function. 0 ___ The glands more active in women and in colored people, more active during pregnancy and menstruation. Their secretions is under the control of sex hormones. NOTE: Any gland open into the hair follicle is under the control of sex hormones. EFEE.no  I self C. SEBACEOUS GLANDS 0 consist of secretory part and duct which Holocrine glands lying adjacent to the hair follicle, open into the hair follicle. Their secretion also stimulated by adrenocortical hormone , progesterone (doubtful), growth hormone and prolactin while estrogen and cyproteron acetate and 13-cis retinoic acid suppress their secretion. They secret sebum which formed aby fatty degeneration and disintegration of large nucleated cells of the glands. AUTH  The glands distributed all over the skin except the palm and sole, exceptionally they may open directly with the epidermal surface as those in the glans penis, the prepuce, the nipples and areola, the labia minora, and the meibomian or palpebral glands of the eyelids. Functions of the sebum: 1-Lubrication of the skin and hair. 2-Protect against physical damage and infections. 3-After puberty it has lethal action on certain fungi. EEE.EE  IT HAIRS  Emberologically; they are epithelial in origin made of modified invaginated epidermal cells. Anatomically each hair follicle consist of infundibulum, isthmus and inferior segment. The follicles and associated sebaceous glands are known as PILOSEBACEOUS UNITS. Hair matrix differentiate into six different layers: 1. Henle,s layer 2. Huxley,s layer ------------------Inner root sheath 3. Cuticle 4. Cuticle of the hair 5. Hair cortex 6. Hair medulla  The mitotic rate of the hair matrix is greater than any tissue except bone marrow. Total number of the hair follicles is five millions, one million in the head,100000 in the scalp. No significant racial difference in the number of the follicles. A significant loss of hair follicles occur with advancing age. The hair contains hard keratin which compose of high sulphur bonds and on hair stretching the keratin takes different pattern.  Types of hair Lanugo hair Lanugo Hair Prenatal coat of fine, soft, unmedullated, usually unpigmented hair shed in 8-9 months of gestation, may retained in Oadult life in hypertrichosis lanuginosa. Vellus hair. y Soft, unmedullated, occasionally pigmented, after puberty secondary sexual terminal hair is develop from vellus hair in response to androgen. µ Terminal hair Longer, coarser, often medullated and pigmented.  HAIR GROWTH CYCLE Cyclic, the growth period called ANAGEN PHASE which varies greatly from species to another and from one region to other and with the age. In the scalp more than 90% are in the anagen phase, The growth of the hair depend on the age of the anagen which is genetically determined. The rate of the growth is 0.3 mm/day or 1cm/mn. The length of the hair is affected by the length of the anagen and the rate of the growth. The age of the anagen in the scalp is 3 years (3-10), hair growth much faster in the children and in summer. CATAGEN PHASE: is the phase of regression. TELOGEN PHASE: is the resting phase in which there is only rudimentary resting hair follicle remain. NAIL O The nail composed of nail plate, nail matrix and nail bed. The nail plate is made of firmly united modified horny cells. Nail matrix consist of modified cells from the stratum Malpighi. Nail bed underlying nail plate consist of modified prickle cells to which the plate is firmly attached. The nail grow continuously in a rate of 0.1 mm/day while the hair grow cyclically with a rate of 0.3 mm/day, Roughly estimated that finger nail takes 3-6 months and toe nail takes 9-12 months to grow from the matrix to the tip of the finger or toe.  SKIN FUNCTIONS 1- Effective protective shield against a wide range of chemical, physical, and biological insults. 2- Effective screen against ultraviolet radiation. 3- Regenerative capacity. 4- Synthesis of vit. D from 7-dehydrocholestrol under light influence. 5- Regulation of the body temperature. 6- Largest sensory organs. 7- Secretory organ through sweat glands. 8- Through melanin content it protect against cancerous and precancerous condition. 9- Through langerhans cells (Antigen presenting cells ),the skin play a role in the immune system. 10-The skin is the organ of personal recognition and sexual attraction. DIAGNOSIS OF SKIN DISEASES  HISTORY Age, Gender, race, residency, occupation. Duration of onset and course of the lesion. shinsympt Relationship of skin lesions to: -season erfEE.at -traveling -drug ingestion -hobbies -heat and cold -previous treatment -occupation -Menses and pregnancy. 000 Skin symptoms: pruritus, pain and paresthesia. Constitutional symptoms. System review. Family history.  PHYSICAL EXAMINATION Appearance of the patient: toxic, well, and uncomfortable. Vital signs: pulse, respiration, temperature. Skin lesions: -Type -Shape O -Arrangement EM'S -Distribution WITH -Color A -Margin inedalvened -Palpation. of Hair and nails. Mucous membranes. General medical examination.  PRIMARY (BASIC) LESIONS 2 5 un Macule :Circumscribed discoloration of the skin less than 0.5 cm diameter. variable in size and shape not elevated e.g. nevus, erythema. o Patch: flat lesion more than 0.5 cm so Papule: A circumscribed palpable elevation less than 0.5 cm in diameter. C 5 Nodule: A circumscribed palpable mass larger than one 0 cm in diameter involving epidermis and dermis and sub cutis or sub cutis alone, on healing it leave a scar. NOTE: Any disease affect only the epidermis it heal without scar while any disease affect the epidermis and dermis result in scar formation. A plaque :A disc-shaped lesion, may be formed by the extension or coalescence of either papules or nodules more than 0.5 cm. said lesion 5cm y  Wheal: Transient circumscribed whitish or pinkish edematous elevation of varying shape represent an area of dermal or dermal and hypo-dermal edema. It is characteristic of urticaria. Vesicle : Visible accumulation of fluid within or beneath the epidermis, less than one cm in diameter. Bullae :Same as the vesicle with a diameter of more than one cm. Pustule : Visible accumulation of pus.  Cyst : A cavity lined by epithelium so all the cavity should be removed to avoid recurrence. Tumor : Circumscribed mass of varying size in the epidermis, dermis or both. Purpura : Free R.B.C in the dermis either less than 1 cm (petechae) or bigger than one cm (Ecchymosis),petechae could be macule or start as macule and end into papule. Telangiectasia : Permanent dilatation of the blood vessels in the dermis.  Secondary Skin lesions Lesions resulted from trauma or bacterial invasion or formed by alteration in the primary lesion  Scales : shaded desquamating epidermal cells. Crust : dried scales, sebum or purulent exudates on the skin surface. It is the hallmark of any pyogenic infection. Ulcer : A circumscribed loss of tissue which may involve the epidermis alone or the epidermis, dermis and underlying tissue. Excoriation : Discontinuation of the skin produced by scratching with finger nails which is either superficial linear or deep. Observe Fissure : Linear cut forming deep linear discontinuation which have sharply defined walls or inflamed basis.  Pigmentation: Discoloration of the skin, normal skin color is due to: melanin, phaeomelanin, haemoglobin, oxyhaemoglobin and carotenoids. Scar : Fibrous tissue replacement of the skin substance which is destroyed by skin disease or trauma. The scar differ in color and texture from normal skin, it may be atrophic or hypertrophic which if last more than three months called keloid. itchykickIRUBI.IQ Lichenification: Hypertrophy of the skin,, hyperpigmentation exaggeration of the normal skin lines, usually occur in chronic skin diseases. o Sclerosis : Diffuse or circumscribed induration of the subcutaneous tissue and may also involve the dermis. Atrophy :depression in the skin surface, resulting from thinning of the epidermis or dermis.  COLOR OF LESIONS Skin lesions could present with many colors like white, red, pink, violaceous, brown, black, blue, grey, yellow, purpuric and others.  PALPATION OF LESIONS consistency ex. Soft, firm, hard, fluctuant, board8 like… temperature whether cold or hot. Mobility consistent Tenderness Tfiid Depth tariff 0 Diascopy: applying pressure on the skin by a finger or glass slide will abolish the erythema, while purpura persists. 0ins0 engineers poofter  SHAPE OF LESIONS shape Round color Round, Maudins oral oval, polyclonal Mobility polygonal, polycyclic, Iris like, annular palpater Feup  MARGIN OF LESIONS Ill defined well defined Regular Irregular  ARRANGEMENT OF MULTIPLE LESIONS om Grouped: ex. Herpetiform, f Herpetign zosteriform, acniform, annular, reticulated (network like), linear (may be caused by Kobner phenomenon) -Kobner phenomenon :is the induction of the same disease process by traumatizing the primary lesion of that disease, ex. Psoriasis, lichen planus, vitiligo, viral warts, eczema, and mulloscum contagiosum. -Disseminated lesions may be scattered, discrete The Koebner phenomenon describes the appearance of new skin or diffuse lesions of a pre-existing dermatosis on areas of cutaneous injury in otherwise healthy skin. It is also known as the Köbner phenomenon and isomorphic response.  DISTRIBUTION OF LESIONS O Extent: ex. Isolated, localized, generalized or universal. Pattern: random, symmetrical or follicular distribution, on exposed areas, sites of pressure, intertriginous areas. LABORATORY AND SPECIAL EXAMINATIONS 1. SKIN BIOPSY (DERMATOPATHOLOGY): light microscopy. Immunofluroscence. Immunohistochemical stains. Electron microscopy.  EPIDERMAL CHANGES Hyperkeratosis :increased thickness of stratum corneum. Parakeratosis: increased thickness of stratum corneum with retained nuclei. Hypergranulosis :increased thickness of stratum granulosum. Acanthosis :increased thickness of stratum spinosum. Spongiosis :accumulation of extra cellular fluid within the epidermis with resultant separation of keratinocytes (i.e. intercellular edema) Acantholysis :separation of cells due to destruction of the intercellular bridges (desmosomes)  Reticular degeneration :intracellular edema resulting in distention and nuclear swelling of keratinocytes. Some cellular membranes may rupture, so forming reticular or mesh – work pattern. Ballooning degeneration :complete swelling of the epidermal cells, that become separated with loss of desmosomes. Liquefaction (hydropic) degeneration of basal layer :formation of vacuolar spaces between and beneath the basilar keratinocytes.  DERMAL CHANGES Type of inflammatory infiltrate (neutrophilic, lymphocytic or periappendegial). Change in dermal thickness. Presence of leucocytoclastic vasculitis which involve small blood vessels with neutrophilic infiltrate, the nuclei of which are fragmented (i.e. called nuclear dust) and deposition of fibrin.  MICROSCOPICAL EXAMINATION OF LESIONS A- Direct microscopical examination: yeasts and fungi: 10 % KOH examination. Bacteria: Gram’s stain. Spirochetes: dark field examination. Parasites: scabie mite from the skin burrows. Viruses: Tzanck smear is microscopical examination of cells from the base of viral vesicles, after being stained with Giemsa’s or Wright’s stain. B- Culture for bacteria, fungi…  LABORATORY. EXAMINATION OF BLOOD -Bacteriologic: culture. -Serologic: ex. Serological tests for syphilis (STS) or antinuclear antibodies (ANA) IF K  IMAGING Exam XR ,US, CT, MRI 3s URINE ANALYSIS. STOOL EXAMINAION for: -Occult blood -Ova and parasites -Porphyrines. PATCH TEST for allergic contact sensitivity  ACETOWHITENING The application of 5% acetic acid to the anogenital area results in whitening of subclinical genital warts. NATO Wood’s light examination  Indications of Wood’s light: Diagnosis, follow up and screening of taenia capitis, giving (greenish florescence). Taenia versicolor (golden yellow). Erythrasma (coral red). Pseudomonas infection (green). Porphyria (red color of teeth). Vitiligo (milky white). Accentuation of white Idor Differentiation between dermal and epidermal types of melasma. Differentiation between nits and scales in patients with pediculosis capitis. THANKS