● The skin
provides an excellent physical barrier which is very hard to penetrate unless broken or cut. The outer epidermis
is principally composed of dead keratinized cells
with plenty of tight junctions
to limit access between them.
- ● Skin secretions principally from hair follicles
- (sebaceous glands) have a ↓pH and contain lactic and fatty acids which all inhibit bacterial growth (so non-hairy skin is more susceptible).
- ● Sweat, tears, saliva and some nasal secretions all
- contain the enzyme lysozyme which is capable of
- destroying the cell walls of certain bacteria. Salinity in sweat may also help.
- ● Modified sweat and sebaceous glands in the external auditory canal of the ear secrete cerumen (ear wax) which like mucus traps dust particles but
- also repels insects.
● The viscosity of mucus
traps many organisms and prevents adherence prior to expelling (coughing, sneezing, etc.). In addition it contains antimicrobial peptides