Integumentary System Quiz

Microbial Diseases of the Skin and Eyes

• Chapter 21 focuses on microbial diseases affecting the skin and eyes.

Skin Structure and Function

• Epidermis: The thin, outer layer of skin, composed of epithelial cells.
• Keratin: A waterproofing protein that coats the epidermis.
• Dermis: The thick, inner layer of skin, mainly composed of connective tissue.

Skin Structure (Figure 21.1)

• The diagram shows the epidermis, dermis, and subcutaneous layers.
• These layers contain hair follicles, oil glands (sebum producers), sweat glands, nerve endings, and blood vessels.

Skin Structure and Function (3 of 3)

• Perspiration: Provides moisture and some nutrients for microbial growth, but also contains salt (inhibits microorganisms), lysozyme (breaks down bacterial cell walls), and antimicrobial peptides.
• Sebum: Secreted by oil glands, contains fatty acids inhibiting pathogens.

Mucous Membranes (1 of 2)

• Line body cavities open to the exterior.
• Tightly packed epithelial cells form an extracellular matrix.
• Cells secrete mucus.
• Some cells possess cilia.
• Often acidic.
• Eyes are washed by tears containing lysozyme.
• Folded to maximize surface area.

Normal Microbiota of the Skin

• Resistant to drying and high salt concentrations.
• Large numbers of gram-positive cocci (Staphylococci, Micrococci).
• Areas with moisture have higher populations metabolizing sweat and contributing to body odor.
• Gram-positive pleomorphic rods (diphtheroids) such as Cutibacterium (Propionibacterium) acnes inhabits hair follicles and is anaerobic.
• Corynebacterium xerosis is aerobic and occupies skin surfaces.
• Yeast, such as Malassezia furfur, causes dandruff.

Microbial Diseases of the Skin

• Vesicles: Small, fluid-filled lesions.
• Bullae: Vesicles larger than 1 cm in diameter.
• Macules: Flat, reddened lesions.
• Papules: Raised lesions.
• Pustules: Raised lesions containing pus.
• Exanthem: Skin rash arising from a disease.
• Enanthem: Rash on mucous membranes arising from a disease.

Staphylococcal Skin Infections

• Staphylococci: Spherical gram-positive bacteria forming irregular clusters.

• Some produce coagulase, an enzyme that clots fibrin in the blood; used to identify types.

• S. epidermidis: Ninety percent of normal skin microbiota; healthcare-associated pathogen; produces biofilm on catheters; coagulase-negative.

• S. aureus: Carried in nasal passages of 20% of the population; golden-yellow colonies; coagulase-positive; produces damaging toxins causing sepsis; avoids host defenses and kills phagocytic cells; MRSA strains are antibiotic-resistant (Vancomycin, VRSA).

• Folliculitis: Infection of hair follicles.

• Sty: Folliculitis of an eyelash.

• Furuncle (boil): A type of abscess, localized pus-filled lesion surrounded by inflamed tissue.

• Carbuncle: Damage/inflammation of deep tissue from a spreading furuncle.

• Impetigo: Crusting skin lesions, spread by autoinoculation.

• Scalded skin syndrome: Bullous impetigo caused by toxin B causing exfoliation.

• Pemphigus neonatorum: Impetigo of the newborn.

• Toxic shock syndrome (TSS): Fever, vomiting, shock, and organ failure caused by toxic shock syndrome toxin 1 (TSST-1).

Streptococcal Skin Infections

• Streptococci: Gram-positive cocci in chains.
• Produce hemolysins lysing red blood cells.
• Beta-hemolytic streptococci often cause disease, with streptococci differentiated by antigenic cell wall carbohydrates into groups A through T.
• Group A streptococci (GAS): Eighty immunological types; produce virulence factors (streptolysins, M proteins, hyaluronidase, streptokinases).
• Erysipelas: S. pyogenes infection of dermal skin layers causing local tissue destruction and sepsis.
• Necrotizing fasciitis: "Flesh-eating" disease rapidly destroying tissue; Exotoxin A is a superantigen.

Infections by Pseudomonads

• P. aeruginosa: Gram-negative, aerobic rod; pyocyanin produces blue-green pus; produces exo- and endotoxins; grows in biofilms.
• Pseudomonas dermatitis: Self-limiting rash acquired in swimming pools; opportunistic in burn patients; resistant to many antibiotics

Buruli Ulcer

• Caused by Mycobacterium ulcerans. Produces the toxin mycolactone. Enters via skin breaks or insect bites. Causes deep, damaging ulcers, and may require amputation. Primarily found in western and central Africa.

Acne

• Most common skin disease in humans.
• Skin cells shed inside hair follicles normally leave, but acne develops when cells shed in high numbers, combine with sebum, and clog follicles.
• Whiteheads (comedos) form, and blackheads (comedones) form if the blockage protrudes through the skin. Lipid oxidation and other causes, not dirt, darken blackheads.
• Sebum formation is affected by hormones, not diet.
• Comedonal (mild) acne: Easily treated with topical formations.
• Inflammatory (moderate) acne: Caused by Propionibacterium acnes metabolizing sebum to form fatty acids causing inflammation. Treated with antibiotics and benzoyl peroxide.
• Nodular cystic (severe) acne: Inflamed lesions with pus deep in the skin.

Viral Diseases of the Skin

• Many viral skin diseases are transmitted via respiratory routes and cause problems in children and developing fetuses.

Warts

• Papillomas are small skin growths transmitted by contact.
• Caused by papillomaviruses; more than 100 types exist. Some cause skin and cervical cancers (HPV types 16 and 18).
• Treatments involve applying extremely cold liquid nitrogen (cryotherapy) or burning with electrical current (electrodesiccation) or salicylic acid.

Smallpox (Variola)

• Caused by an orthropoxvirus.
• Two forms: Variola major (20–60% mortality), Variola minor (<1% mortality).
• Transmitted via respiratory route and enters bloodstream; infects the skin.
• Completely eradicated by vaccination.
• Potential bioterrorism agent. -Related to monkeypox, which is endemic to small animals in Africa; jumps to humans; prevented by smallpox vaccination.

Chickenpox (Varicella) and Shingles (Herpes Zoster)

• Chickenpox (varicella): Herpesvirus varicella-zoster, transmitted via respiratory route; causes pus-filled vesicles; Reye's syndrome as severe complications of chickenpox (aspirin use increases risk), virus becomes latent in central nerve ganglia; prevented by a live attenuated vaccine; outbreak possible in vaccinated individuals (breakthrough varicella).
• Shingles (herpes zoster): Reactivation of latent varicella-zoster virus, moves along peripheral nerves to the skin; due to stress or lower immunity; follows the distribution of affected cutaneous sensory nerves; limited to one side; causes postherpetic neuralgia; Prevention via the zoster vaccine, antiviral drugs to lessen symptoms.

Herpes Simplex

• Human herpesvirus 1 (HSV-1) and 2 (HSV-2) spread through oral/respiratory or sexual routes, respectively.
• Ninety percent of the U.S. population is infected with HSV-1; develops as cold sores or fever blisters.
• HSV-1 remains latent in trigeminal nerve ganglia, outbreaks triggered by sun, stress, or hormonal changes.
• HSV-2 remains latent in sacral nerve ganglia.
• Women with HSV-2 should deliver by caesarian, Herpes gladiatorum (skin vesicles). Herpetic whitlow (finger vesicles), Herpes encephalitis (virus spreading to brain), and treatment with acyclovir.

Measles (Rubeola)

• Viral disease transmitted by the respiratory route.
• Cold-like symptoms and macular rash.
• Koplik's spots (red spots on oral mucosa).
• Encephalitis in about 1 in 1,000 cases.
• Subacute sclerosing panencephalitis.
• Rare; occurs 1 to 10 years after measles recovery. Prevented by the MMR vaccine (not recommended for pregnant women; children under one year cannot normally receive the vaccine).

Rubella

• German measles caused by Rubella virus.
• Macular rash and light fever. Respiratory transmission with 2-to-3 week incubation.
• Congenital rubella syndrome: fetal damage, deafness, heart defects, mental retardation in 35% and 15% mortality within the first year of life. Prevented by the MMR vaccine; not recommended for pregnant women.

Other Viral Rashes

• Fifth disease (erythema infectiosum): Caused by human parvovirus B19, mild flu-like symptoms, "slapped-cheek" facial rash.
• Roseola: Caused by human herpesviruses 6 and 7, high fever followed by a body rash, recovery within 1-2 days

Hand-foot-and-mouth disease

• Caused by enteroviruses.
• Spread via mucous or saliva, usually affecting children.
• Symptoms include fever, sore throat, and rash on hands, feet, and mouth.

Fungal Diseases of the Skin and Nails

• Mycosis: Fungal infection of the body.
• Cutaneous Mycoses: Colonize hair, nails, and outer epidermis. Metabolize keratin.
• Dermatomycoses: Informally known as tineas or ringworm;
• Include Tinea capitis (scalp); Tinea cruris (jock itch); Tinea pedis (athlete's foot); and Tinea unguium (ringworm of nails).
• Genera of fungi including: Trichophyton; Microsporum; Epidermophyton.
• Treatment is usually with topical drugs (miconazole, clotrimazole).

Subcutaneous Mycoses

• More serious than cutaneous mycoses.
• Penetrate the stratum corneum.
• Usually caused by fungi that inhabit the soil.
• Sporotrichosis: Caused by Sporothrix schenckii, a dimorphic fungus. Enters a wound, and forms a small ulcer. Treated with potassium iodide.

Candidiasis

• Overgrowths by C. albicans.
• C. albicans forms pseudohyphae, resistant to phagocytosis.
• Occurs in skin & mucous membranes of genitourinary tract and mouth. -Thrush, a whitish overgrowth of the oral cavity, affects newborn infants with underdeveloped microbiota.
• Candidiasis occurs when antibiotics suppress competing bacteria, or when mucosal pH changes.
• Causes fulminating disease in immunosuppressed people.

Parasitic Infection of the Skin

• Scabies: Caused by Sarcoptes scabiei mites, which burrow into the skin to lay eggs.
• Causes inflammatory skin lesions.
• Spread through intimate contact
• Treatment with permethrin.

Pediculosis (Lice)

• Pediculus humanus capitis (head louse) and P. h. corporis (body louse).
• Feed on host blood, laying eggs (nits).
• Attach to hair shafts.
• Treated with topical insecticides (permethrin, pyrethrin, malathion, lindane, or ivermectin in cases of resistance).

Microbial Diseases of the Eye

• Conjunctivitis: Inflammation of the conjunctiva; also called red eye or pink eye; commonly caused by Haemophilus influenzae, adenoviruses, or pseudomonads (unsanitary contact lenses).
• Ophthalmia Neonatorum: Caused by Neisseria gonorrhoeae. Large pus amount forms; ulcerates cornea; can cause blindness (treated with antibiotics).
• Inclusion Conjunctivitis: Caused by Chlamydia trachomatis. Obligate intracellular bacteria; spread through swimming pool water and transmitted to newborns during birth. Treate with tetracycline.
• **Trachoma:**Caused by several Chlamydia trachomatis serotypes. World-leading cause of blindness. Transmitted by hand contact or flies. Infection causes permanent scarring; abrade cornea, leading to blindness (secondary infections can worsen the problem). Oral azithromycin in treatment.
• Keratitis: Inflammation of cornea.
  • Bacterial (United States).
  • Fungal (Fusarium and Aspergillus, common in Africa and Asia).
  • Herpetic keratitis: Caused by herpes simplex virus 1 (HSV-1). Affects cornea; can cause blindness, treated with trifluridine.
  • Acanthamoeba keratitis: Transmitted through water and soil; associated with unsanitary contact lenses. Mild inflammation initially, followed by severe pain. Treatment with 2% chorhexidine and propamidine isethionate eye drops or topical neomycin. May require corneal transplant.

Test your knowledge on the integumentary system, focusing on the skin's composition and functions. This quiz includes questions about the roles of keratin, enzymes in perspiration, and various types of staphylococci. Explore the key elements that contribute to skin health and microbial interactions.