Non-specific disease resistance mechanisms & Skin's defense barriers




• Non-specific disease resistance acts quickly to fight a wide variety of invaders. • Mechanisms include: • Barriers • Antimicrobial substances • Cellular defenses • Inflammation • Fever Barriers - types • Physical and chemical bathers prevent invasion by microbes. ▪ Physical barriers: • Skin. • Eye structures. • Digestive mucosa. • Respiratory mucosa. • Genitourinary mucosa. • Chemical barriers: • Perspiration. • Keratin. • Tears. • Lysozyme. Barriers - skin's physical defense • The body's major physical barrier to microbes is the skin. • The scaly tissue that forms the epidermis (keratinized stratified squamous epithelium) makes it difficult for microbes to penetrate the skin. • The most superficial layer of the skin is continuously sloughed off, removing live and dead microbes. Barriers - skin's chemical defense • The skin also provides effective chemical barriers. • Sebum: • Produced by sebaceous glands. • Inhibits bacterial growth. • Perspiration: • Produced by the sudoriferous glands. • Inhibits bacterial growth. • Contains lysozyme, which breaks down bacteria. Barriers - skin's cellular defense • The skin's cellular defense: Macrophages in the skin phagocytize microbes, preventing further invasion.



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