1. physical structure
1.1. skin
1.1.1. 3 layers
1.1.1.1. epidermis - thin upper layer
1.1.1.1.1. keratin makes the skin surface mechanically tough and resistant to degration by bacterial enzymes
1.1.1.1.2. fatty acids make a dry, salty, acidic environment to inhibit microbial growth
1.1.1.1.3. dead top layer sheds for a new protective barrier
1.1.1.2. dermis - second thick layer with hair follicles, sweat glands, nerves, and blood vessels
1.1.1.3. hypodermis - third fatty tissue layer with blood and lymph vessels
1.2. mucous membranes
1.2.1. layers of epithelial cells bound by tight junctions
1.2.1.1. secretes mucus which is a moist, sticky substance that covers cell layers and traps debris and microbes
1.2.1.2. contain antimicrobial peptides
1.2.2. lines the nose, mouth, lungs, urinary tract, and digestive tracts
1.2.2.1. respiratory system
1.2.2.1.1. inhalation can allow an entry way for microbes, spores, and other debris that will be caught in the mucus lining
1.2.2.1.2. mucociliary blanket
1.2.2.1.3. ciliated epithelial cells with cilia to send out debris in the mucus out of the lungs
1.2.2.1.4. mucociliary elevator
1.2.2.2. digestive tract
1.2.2.2.1. intestinal tract lined with epithelial cells interspersed with mucus-secreting goblet cells
1.2.2.2.2. peristalsis
2. chemical mediators
2.1. human microbiome
2.1.1. exogeneous
2.1.1.1. oleic acid - creates a mildly acidic environment to inhibit pathogenic microbial growth on the surface of the skin
2.1.1.1.1. exogeneous because created by resident microbe, not body cells
2.1.2. endogenous
2.1.2.1. sebum - oil secreted by sebaceous glands in the dermis onto the skin surface through hair follicles
2.1.2.1.1. seals off pore of hair follicle to prevent bacteriafrom entering the sweat glands and other tissues
2.1.3. environmental factors affecting skin has a direct impact on chemical mediators
2.1.3.1. low humidity or decreased sebum - less habitable for microbes
2.2. digestive tract
2.2.1. oral cavity
2.2.1.1. saliva
2.2.1.1.1. lactoperoxidase enzymes
2.2.1.1.2. lysozyme - antibacterial enzyme in the mucus secreted by esophagus
2.2.2. stomach
2.2.2.1. gastric fluid - extremely acidic and kills most microbes
2.2.3. intestines
2.2.3.1. pancreatic and intestinal enzymes
2.2.3.2. antibacterial peptides ex cryptins
2.2.3.3. bile
2.2.3.3.1. produced from liver
2.2.3.4. Paneth cells
2.2.3.4.1. produce lysozyme
2.3. urinary tract
2.3.1. urine flushes microbes out through urination
2.3.1.1. average pH of 6 to inhibit microbial growth and pathogens
2.4. eyes
2.4.1. tears contain lysozyme and lactoferrin
2.4.1.1. eliminates microbes on the surface of the eyes