Integumentary System Pathophysiology PDF

INTEGUMENTARY SYSTEM AND PATHOPHYSIOLO GY Dr LSK 1  RECALL: MEMBRANES & INTEGUMENTS Membrane. A thin sheet or layer of pliable tissue, serves as a covering or envelope of a part, as the lining of a cavity, as a partition or septum, or to connect tw...

INTEGUMENTARY SYSTEM AND PATHOPHYSIOLO GY Dr LSK 1  RECALL: MEMBRANES & INTEGUMENTS Membrane. A thin sheet or layer of pliable tissue, serves as a covering or envelope of a part, as the lining of a cavity, as a partition or septum, or to connect two structures. Three types: 1. Cutaneous membrane – skin The cutaneous membrane is simply referred to as the skin. 2. Mucous membrane Lines of hollow organs that open to the surface of the body An epithelial sheet underlain with a layer of lamina propria 3. Serous membrane – slippery membranes Simple squamous epithelium lying on areolar connective tissue Line closed cavities Pleural, peritoneal, and pericardial cavities  INTEGUMENTARY SYSTEM Cutaneous membrane (skin) – our largest organ Accounts for 7% of body weight 1/3 of cardiac output is directed to skin Surface area 18-20 Sq Ft Thickness 1.5-4mm Divided into two distinct layers Epidermis Dermis Accessory structures Subcutaneous layer (hypodermis) 3  FUNCTIONS OF THE INTEGUMENTARY SYTEM Cushions and insulates deeper organs Protects the body from abrasion, trauma, chemicals, pathogens, temperature extremes, and UV rays. Excretion and secretion Contains sensory receptors associated with nerve endings (sensation). Synthesis and storage of nutrients (vitamin D3). Thermoregulation Absorption 4 INTEGUMENTARY STRUCTURES Components of the Integumentary System 7 Figure 5-1 SKIN STRUCTURES 6  THE EPIDERMIS Stratified squamous epithelium ( Keratinized) Several distinct cell layers Thick skin—five layers on palms and soles Thin skin—four layers on the rest of the body (absent of stratum lucidum) 7  LAYERS OF THE EPIDERMIS Stratum corneum Most superficial layer Dead, flattened (squamous) cells Abundant keratin - Keratinized (cornified) tough, water-resistant protein Protects skin against abrasion and penetration Stratum lucidum (clear layer) Occurs only in thick skin – palms and soles Composed of a few rows of flat, dead keratinocytes 1 0  CLASSIFICATION OF BURNS By depth By Surface area of skin burnt: 9 CLASSIFICATION OF BURNS ACCORDING TO DEPTH (THICKNESS OF SKIN INVOLVED) First-degree burn – only upper epidermis is damaged Second-degree burn – upper part of dermis is also damaged Blisters appear Skin heals with little scarring Third-degree burn Consume thickness of skin Burned area appears white, red, or blackened Fourth degree extends through skin, subcutaneous tissue and into underlying muscle and bone; ( usually becomes black) 10  CLASSIFICATION OF BURNS BY SURFACE AREA OF SKIN BURNT Burns can also be assessed in terms of total body surface area (TBSA), which is the percentage affected by partial thickness or full thickness burns. Estimating burns using the Rule of Nines for adult patients & Rule of Sevens for children; the rule of nines or sevens is used as a quick and useful way to estimate the affected TBSA. The size of a person's hand print (palm and fingers) is approximately 1% of their TBSA Burns of 10% in children or 15% in adults (or greater) are potentially life threatening injuries (because of the risk of hypovolaemic shock) and should have formal fluid resuscitation and monitoring in a burns unit. Burns units will use surface area to predict severity and mortality using a 11 ESTIMATING BURNS USING THE RULE OF NINES Figure 55.511a  THE SKIN THROUGHOUT LIFE Epidermis Develops from embryonic ectoderm Dermis and hypodermis Develop from mesoderm Melanocytes Develop from neural crest cells 13 THE EPIDERMIS- FOUR MAIN CELL TYPES 1. Melanocytes - found in basal layer, manufacture and secrete pigment 2. Merkel cells - basal layer, attached to the sensory nerve endings 3. Keratinocytes – Arise from The deepest layer of the epidermis to stratum spinosum Produce keratin – a tough fibrous protein Produce antibodies and enzymes Keratinocytes are dead at the skin's surface 4. Langerhans cells - stratum 14 FUNCTIONS OF THE EPIDERMIS Provides a physical & chemical barrier Regulates fluid Provides light touch sensation Assists with thermoregulation Assists with excretion Assists with vitamin D production Contributes to appearance BASEMENT MEMBRANE ZONE: DERMO-EPIDERMAL JUNCTION Where epidermis and dermis join Contains many proteins and structures Site of inflammation in many diseases Important in skin neoplasia ( usual growth of cells in the skin. E.g skin cancer  SOURCES OF SKIN COLOR Melanocytes Make melanin from tyrosine Melanin provides UV protection Gives reddish-brown to brown- black color Carotene Contributes orange-yellow color Provided from diet (carrots and tomatoes) Hemoglobin - blood pigment Caucasian skin contains little melanin Allows crimson color of 17 blood to show through DERMIS Second major layer of the skin Provides mechanical strength, flexibility, and protection for underlying tissues Highly vascular and contains a variety of sensory receptors that provide information about the external environment. Two layers: Papillary layer – includes dermal papillae Reticular layer - deeper layer – 80% of the thickness of dermis 18 The structures in the dermis are: Blood vessels Lymph vessels Sensory (somatic) nerve endings Sweat glands and their ducts Hairs, arrector pili muscles and sebaceous glands 19  Structures in the Dermis RECEPTORS AND THEIR STIMULI Meissner's corpuscle…Light pressure Pacinian corpuscle...Deep pressures Ruffini nerve corpuscle… thermoreceptor & stretch receptors 20  FUNCTIONS OF THE DERMIS  Support & nourish epidermis  House epidermal appendages  Assists with infection control  Assists with thermoregulation  Provides sensation 21 SUBCUTANEOUS LAYER - HYPODERMIS Composed of loose connective tissue - areolar and adipose it stabilises skin position Loosely attached to dermis Loosely attached to muscle Contains many fat cells Provides thermal insulation Cushions underlying organs Safely receives hypodermic needles 22 HAIR FUNCTION AND DISTRIBUTION Functions of hair include: Helping to maintain warmth Alerting the body to presence of insects on the skin Guarding the scalp against physical trauma, heat loss, and sunlight Hair is distributed over the entire skin surface except Palms, soles, and lips Nipples and portions of the external genitalia 23  GLAN DS Three types of glands in the skin: Sebaceous glands (oil) Sudoriferous glands (sweat) Ceruminous glands (cerumen/wax) Function is to help regulate the body temperature and excrete body wastes 24 SWEAT (SUDORIFEROUS) GLANDS Two types: Eccrine (Merocrine) Most abundant sweat gland “True sweat” 99% water with some salts Contains traces of metabolic wastes ~ 2% urea Role in thermoregulation Widely present in skin (up to 500/cm2) Apocrine Odorous secretion Absent before puberty 25 THE SKIN THROUGHOUT LIFE: AGING Fetal skin Well formed after the fourth/fifth month At 5-6 months The fetus is covered with lanugo (downy hairs) Fetal sebaceous glands produce vernix caseosa 26  AGING OF THE SKIN Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows 27  SKIN AND THERMOREGULATION The thermoregulation refers to four mechanism 1. Sweating- it increases body heat loss by increasing sweat evaporation 2. Shivering- Produces heat by involuntary movement of muscle 3. Vasodilation- for heat loss from the body- hot weather 4. Vasoconstriction- conserve the body heat- cold weather Both Vasodilation and vasoconstriction refer to changes the rate of blood vessel diameter, which affect skin temperature by changing the rate of blood exchange with the interior. SKIN INFECTION Only a few species of bacteria commonly invade the intact skin directly, which is not surprising in view of the anatomical and physiological features discussed previously. Skin and soft tissue infection ( SSTI) SSTIs can be defined as an inflammatory microbial invasion of the epidermis, dermis and subcutaneous tissues. The presence of bacteria over the skin surface doesn’t mean that this microbe is responsible for the pathology  PATHOPHYSIOLOGY OF THE INTEGUMENTARY SYSTEM Skin and soft tissue infection ( SSTI) A. General SSTI can be classified into two: 1. Purulent infections: ( folliculitis, furunculosis and skin abscesses ) 2. Non-Purulent infections: ( Erysipelas, cellulitis and necrotizing fasciitis B. It can also be classified based on the depth of infection 3. Most Superficial infections: impetigo, erysipelas and Folliculitis 4. Deep localized infections: furunculosis (associated with hair follicle), hidradenitis (associated with sweat gland and skin gland). C. It can be classified based on the severity of the illness Deeper infections such as necrotizing fasciitis and myonecrosis. These can lead to sepsis and irreversible septic shock Classification Of Skin SCHEMATIC OF THE ANATOMIC SITES OF SOFT TISSUE IN FECTION  SUMMARY AND APPROACHES Superficial infections can be handled with outpatient treatment a. Most Superficial infections: impetigo, erysipelas and Folliculitis b. Deep localised infections: furunculosis, hidradenitis and skin abscesses Deeper infection: it requires hospitalisation, parenteral antibiotics, and possibly surgical debridement a. Cellulitis is the most superficial and can be treated with systemic antibiotics alone. b. Necrotising fasciitis involves the fascia and requires emergent surgery. c. Myonecrosis (gas gangrene): also requires rapid surgical debridement; it is often fatal. HAIR FOLLICLE INFECTIONS Infections originating in hair follicles commonly clear up without treatment. In some instances, however, they progress into severe or even life-threatening diseases. E.g: Folliculitis that's caused by staph can start to grow inside your body. Over time, it can spread to your organs and blood. While this is uncommon, it can be deadly if not treated properly.  SYMPTOMS Folliculitis, furuncles, and carbuncles represent different outcomes of hair follicle infections. In folliculitis, a small red bump, or pimple, develops at the site of the involved hair follicle. Often, the hair can be pulled from its follicle, accompanied by a small amount of pus, and then the infection goes away without further treatment. However, the infection extends from the follicle to adjacent tissues, causing localised redness, swelling, severe tenderness, and pain, the lesion is called a furuncle or boil.  CAUSATIVE AGENT Most furuncles and carbuncles, as well as many cases of folliculitis, are caused by Staphylococcus aureus. One of the most useful identifying characteristics of S. aureus is that it produces a protein called coagulase. This protein product of S. aureus is largely extracellular. It reacts with the blood component Prothrombin, resulting in a complex called Staphylothrombin. This causes blood clotting by converting fibrinogen to fibrin. Some coagulase is tightly bound to the surface of the bacteria and coat their surface with fibrin upon contact with blood. RISK OF INFECTION 2-Infection agent : -Virulence -Numbers 1-Host : -Diet – vit.C. -Extreme age. -Chronic illness. -D.M, CLD, CRF Virulence: The ability -Medications: Steroid -Impaired immunity: of an agent of infection HIV to produce disease. 3-Battle ground wound : -Ischemia -Necrosis -Gangreneous -Decrease WBC ,Abs  SOFT TISSUE INFECTIONS Superficial (skin and subcutanous) :- -Boils -Carbuncle -Folliculitis -Impetigo -Erysipelas -Cellulitis -Abcess -Deep ( Fascia & Muscle) :- -Necrotizing Fasciitis -Gas gangrene Organs :- -Cholecystitis -Appendicitis Not part of the skin but they are soft tissue infections. SUPERFICIAL (SKIN AND SUBCUTANOUS) 1- Boils (furuncle): it is an infection of the single hair follicle. Carbuncle: a cluster of boils, usually painful, pus-filled bumps that form a connected area of infection under the skin. 2- Folliculitis is an infection of a group of hair follicles. Mostly caused by bacteria, the condition can be itchy, sores and crusty sores Mild folliculitis can heal without scaring in a few days with basic self-care More serious or repeated infection may need treatment, If more serious cases are left untreated, it can cause permanent hair loss and scarring. Types: 1. Superficial: involves the upper part of the follicle 2. Deep: involves the entire follicle and is usually severe.  IMPETIGO 3- Impetigo: a contagious disease common in infants and young children. Usually appears as reddish sores on the face, especially the nose and mouth. It’s a staphylococcus or streptococcus infection, which presents with honey-colored crusts skin after blisters rupture. Rx: by direct washing, tropical Antibiotics, oral Antibiotics  ERYSIPELAS 4 –Localized cellulitis) sharply demarcated streptococcal infection of lymphatic vessels, usually associated with broken skin on the face, erythema, and Oedema  It involves the dermal layer of the skin It may extend to the superficial cutaneous lymphatics It is characterised by erythema that is well-demarcated. Often affects the lower extremities and face, being the second. It affects both children and adult Rx : broad spectrum Antibiotics  5-CELLULITIS - Is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken. - It causes by both staph and streptococcus  SUMMARY FOR CELLULITIS 1. An infection of the skin, with some extension to the subcutaneous tiss ues. 2. Predisposing factors include venous or lymphatic insufficiency, diabetes mellitus, alcoholism, penetrating wounds, and eczema or other inflammatory skin diseases. 3. Characteristics include erythema (redness of skin), edema, diffuse tenderness, indistinct border, and lymphadenopathy. 4. Caused by streptococci (nonpurulent) and S. aureus (purulent). Haemophi lus influenzae is a possible cause in children. 5. Subclasses of cellulitis include a. erysipelas (more superficial; very sharp, raised border), b. clostridia cellulitis (associated with crepitation, no muscle involvement), a nd c. anaerobic cellulitis (foul- smelling, more common in patients with diabetes).  CASE OR LIKELY APPLIED QUESTION Following trauma to his right shin, a 50-year-old man experienced the acute onset of pain and erythema that rapidly spread over his entire leg and was accompanied by fever and chills. On examination, he appeared moderately ill; there was local adenopathy, and diffuse erythema and edema of his entire right leg. The margins were indistinct, and no purulence was noted. He had a leukocytosis with a left shift, and blood cultures were positive for Streptococcus pyogenes. Classify the type of skin infection?  6-Skin Abcess - Is a collection of pus (dead neutrophils) that has accumulated in a cavity formed by the tissue in which the pus resides on the basis of an infectious process (usually caused by bacteria or parasites)  7-Carbuncle - Is an abscess larger than a boil, usually with one or more openings draining pus onto the skin.  DEEP ( MUSCLE & FASCIA) 1- Necrotizing fasciitis : Flesh-eating disease or Flesh-eating bacteria syndrome, is a infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the fascial plane within the subcutaneous tissue  SUMMARY FOR NECROTIZING 1. FASCIITIS This deep subcutaneous infection causes necrosis of the fascia and subcut aneous fat. 2. Causes include mixed infection with gram­-positive and gram- negative aerobes and anaerobes (type I) or group A streptococci or CA­- MRSA (type II) 3. Severe pain is often the earliest symptom; septic appearance and tachycar dia are also suggestive. 4. Laboratory data: C.Reactive.protein, WBC, Hgb, serum Na, creatinine, and glucose can be u sed to create a risk score; LRINEC >5, low risk for NF, ≥6-7 points moderate risk, ≥ 8, high-risk chance of having a necrotizing soft tissue infection. 5. Surgical exploration (preferred) or punch biopsy are required for diagnosis. 6. Treatment must include the following: a.  DEEP ( MUSCLE & FASCIA) 2 – Gas gangrene : is a bacterial infection that produces gas tissues in gangrene. It is a deadly form of gangrene usually caused by anaerobic bacteria. It is a medical emergency.  DEEP ORGANS -Appendicitis. -Acute cholecystitis  HINTS Two microorganisms are responsible for most cutaneous infections in immun ocompetent patients: 1. Beta-hemolytic streptococcus (groups A, B, C, G, and F). 2. Staphylococcus aureus, including community­acquired methicillin­- resistant S. aureus (CA­MRSA). Deeper infection: it requires hospitalization, parenteral antibiotics, and possibly surgical debridement e.g: Necrotizing fasciitis and Myonecrosis SKIN CANCE R Basal cell carcinoma Least malignant and most common Squamous cell carcinoma Arises from keratinocytes of stratum spinosum Melanoma A cancer of melanocytes The most dangerous type of skin cancer 53 Skin Cancer Squamous cell Squamous cell carcinoma carcinoma Basal cell carcinoma Melanoma Figure 652.12 DISORDERS OF THE INTEGUMENTAR SYSTEM (CONTINUED) Cellulitis – Bacterial infection of the dermis and subcutaneous layer of the skin Chloasma (melasma) – Patchy discoloration of the face Cleft lip or cleft palate – Upper lip has a cleft where the nasal palate doesn’t meet properly Contact dermatitis – Allergic reaction that may occur after initial contact or as an acquired response 55 DISORDERS OF THE INTEGUMENTAR SYSTEM (CONTINUED) Eczema – Group of disorders caused by allergic or irritant reactions Fungal skin infections – Skin infections that live on dead outer surface or Epidermis - 56 DISORDERS OF THE INTEGUMENTARY SYSTEM (CONTINUED) Skin cancer – Three forms are basal, squamous, and melanoma Skin lesions – Differ in texture, color, location, and rate of growth Streptococcus – Nonmotile bacteria that affect many parts of the body 57  DISORDERS OF THE INTEGUMENTARY SYSTEM Acne vulgaris – Caused by increased secretion of oil related to increased hormones during puberty Albinism – Inherited disorder in which melanin is not produced Alopecia – Baldness Athlete’s foot – Contagious fungal infection of the foot 58 EN D 59 PRACTISE QUESTIONS This 63-year-old man presents with the acute onset of moderate swelling and severe tenderness of the right foot. He appeared severely ill with high fever, tachycardia, and hypotension accompanied by severe pedal edema and erythema with one discrete 1×1 cm deep red lesion. Laboratory exam revealed marked leukocytosis, and surgical exploration revealed necrotic fascia. State the type of skin infection.