ch. 16

• What does the integument form?


  Boundary between the human and the environment
• What structures form the integument?

  Skin, hair, nails, sweat and oil glands
• What is the total surface area of the skin?

  1.5 to 2 square meters
• How does the thickness of the skin vary?

  From 1.5 mm at the eyelids to 4 mm on the soles of the feet
• 25 cells thick, dead cells that have migrated from deeper layers

  Stratum corneum
• What does the integument form?

  Boundary between the human and the environment
• What structures form the integument?

  Skin, hair, nails, sweat and oil glands
• What is the total surface area of the skin?

  1.5 to 2 square meters
• How does the thickness of the skin vary?

  From 1.5 mm at the eyelids to 4 mm on the soles of the feet
• 25 cells thick, dead cells that have migrated from deeper layers

  Stratum corneum
• - Millions of these cells slough off daily, shedding microorganisms with them.

  - Entire _______ is replaced every 25 to 45 days

  Epidermis
• - Contains fibroblast cells, collagen, macrophages, and mast cells

  - Contains nerves, blood vessels, and lymphatic vessels

  Dermis
• What happens when damage penetrates the dermis?

  Broken blood vessels
• What causes blister formation between the epidermis and dermis?

  Friction, trauma, or burns
• What are antimicrobial peptides?

  Positively charged chemicals that act by disrupting the negatively charged membranes of bacteria
• How do antimicrobial peptides help in immunity?

  They are chiefly responsible for keeping the microbial count on the skin relatively low and are part of the innate immune response
• What is the role of sebum's low pH in skin health?

  It makes the skin inhospitable to microorganisms
• What makes sebum oily?

  Its high concentration of lipids
• How do lipids in sebum contribute to skin health?

  They serve as nutrients for normal microbiota
• Inhibitory to microorganisms due to low pH and high salt concentration

  Sweat
• Where is lysozyme found in the body?

  Sweat, tears, and saliva
• What does lysozyme specifically break down?

  Peptidoglycan in bacterial cell walls
• Defenses of the Skin

  Antimicrobial peptidesSebumSweatLysozyme
• Characteristic of Normal Skin Biota

  Must be capable of living in dry and salty conditions
• Where Normal Skin Biota Grow in Dense Populations

  Moist areas and skin folds such as underarm and groin
• normal skin biota

  Hair follicles and glandular ducts
• Streptococcus, Staphylococcus, Corynebacterium, Propionibacterium, Pseudomonas, Lactobacillus;

  yeasts such asCandidaNormal Biota of the Skin
• - Common cause of skin lesions in non-hospitalized people

  - Staphylococcus aureusCharacteristics of MRSA
• What is the morphology of Staphylococcus aureus?

  Gram-positive coccus that grow in clusters; nonmotile
• How is Staphylococcus aureus classified in terms of its virulence?

  Can be highly virulent, but is also considered 'normal' biota of the skin in some of the population
• Is Staphylococcus aureus often pathogenic?

  Yes
• What are the common skin symptoms of MRSA?

  - Raised, red, tender, localized lesions

  - Features pus and feels hot to the touch

  - Occur easily in breaks in the skin and may localize around a hair follicle
• What systemic symptom is commonly associated with MRSA?

  Fever
• - Commonly found on human skin

  - not usually pathogenic

  Staphylococcus epidermidis
• Where can MRSA be found on surfaces?

  Gym equipment, airplane tray tables, electronic devices, razors, etc.
• How can persons with active MRSA skin lesions prevent transmission?

  They should keep them covered.
• Staph aureus

  is coagulase positive
• Staph epidermidis

  is coagulase negative
• is an enzyme that coagulates plasma

  Coagulase
• contains high salt (7%) and is selective for gram-positive Staphylococcus species

  Mannitol salt agar (MSA)