PHSC1312 Microbiology/Immunology Lecture 3 Innate Physical Barriers

epithelial cells, mucus, fluids, ciliary action

mechanical physical barriers

skin, GI, urogenital, and respiratory tracts

Where are epithelial cells found?

tight connections and regular desquamation

How do epithelial cells act as a physical barrier?

desquamation

turnover or shedding of cells

coating respiratory, gastrointestinal, and urogenital epithelial cells

Where is mucus found?

mucins

glycoproteins that make the surface difficult for attachment and growth

makes surface difficult for attachment and growth

How does mucus act as a physical barrier using mucins?

tears, saliva, sweat, and urine

types of fluids that act as a physical barrier

flush over surfaces to prevent microbe attachment

How do fluids act as physical barriers?

ciliary action

physical barrier in the airways that move things up

peristalsis

forward movement in the gut that acts as a physical barrier

antimicrobial peptides, sweat, lysozyme and phospholipase, surfactant, hydrochloric acid

physical chemical barriers

alpha in gut and beta in lung

Where are defensins?

defensins

small cationic peptides that disrupt bacterial, fungal, and some viral membranes

fatty acids and low pH

features of sweat that help prohibit bacterial growth

lysozyme and phospholipase

found in tears, saliva, and nasal secretions; breaks down bacterial cell walls and destabilizes bacterial membranes

tears, saliva, and nasal secretions

Where are lysozyme and phospholipase found?

surfactant

produced by lung lipoprotein; reduces surface tension and prevents collapse

hydrophobic peptides and collectins opsonize

components of surfactant

hydrophobic peptides

part of surfactant; helps reduce surface tension

collectins

part of the surfactant that coats pathogens to enhance their uptake and destruction by phagocytic cells like macrophages and neutrophils

skin and gastric pH

What has HCl to inhibit growth of bacteria?

resident flora, antibodies in circulation

biological physical barriers

microbiota on the skin, GI tract, urogenital tract, and respiratory tract

What does the resident flora involve?

IgG and IgA

antibodies in circulation

in circulation

Where is IgG most abundant?

within mucosa

Where is IgA mostly present?