6. Nose Hair: Coated with mucus filter dust, pollen, and microbes. 7. Ciliary Escalator: Cilia on mucous membranes of lower respiratory tract move upwards towards throat at 1-3 cm/hour.
A. Mechanical Defenses 8. Coughing and sneezing: Expel foreign objects. 9. Epiglottis: Covers larynx during swallowing. 10. Urination: Cleans urethra. 11. Vaginal Secretions: Remove microbes from genital tract.
Epiglottis Protects Respiratory System from Infection During Swallowing
B. Chemical Defenses: – Sebum: Oily substance produced by sebaceous glands that forms a protective layer over skin. Contains unsaturated fatty acids which inhibit growth of certain pathogenic bacteria and fungi. – pH: Low, skin pH usually between 3 and 5. Caused by lactic acid and fatty acids. – Perspiration: Produced by sweat glands. Contains lysozyme and acids. – Lysozyme: Enzyme that breaks down gram- positive cell walls. Found in nasal secretions, saliva, and tears.
B. Chemical Defenses (Continued) – Gastric Juice: Mixture of hydrochloric acid, enzymes, and mucus. pH between 1.2 to 3 kills many microbes and destroys most toxins. Many enteric bacteria are protected by food particles. • Helicobacter pylori neutralizes stomach acid and can grow in the stomach, causing gastritis and ulcers. – Transferrins: Iron-binding proteins in blood which inhibit bacterial growth by reducing available iron.
1. Innate Immunity non-specific, pre-formed and fully active, can function immediately upon the entry of pathogens, inherent capability of the organism to offer resistance against invaders, consists of defensive barriers has two lines of defence PMN ( Polymorphonuclear leucocytes) ingest and destroy many different bacteria skin and membrane serve as the 1st line of defense against pathogens innate immune cells function as the 2nd line of defense
Other Nonspecific Defenses: Interferon: Released by virus-infected cells. • warns neighboring cells of invader • neighboring cells produce an enzyme to slow viral synthesis Fever: When the body’s temperature rises. • stimulates the immune system • inhibits some bacterial growth High temperatures are dangerous! • Proteins (including enzymes) denature at approx. 108 degrees.
Other mechanisms of Defense... • Physiological variables – pH of our environment – temperature of our environment • chemical defenses – nitric oxide, enzymes, proteins, complement • AND the IMMUNE SYSTEM…
Innate immune cells ● Neurophils, phagocytosis and destroying of bacteria ● Macrophages/dendritic cells, phagocytosis, and can function as antigen presenting cells (APC) presenting peptide antigens to T cells and B cells (facilitating adaptive immune response). ● An emerging new field, Toll-like receptors (TLR) expressed on macrophages/dendritic cells. TLR-1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 confer pattern recognition of some bacterial molecules, and cellular signals (activation of proteins/enzymes) trigger innate and adaptive immune responses. Discovery of TLR function changes the paradigm “innate immunity is not specific” ● NK (nature killer) cells, γδ T cells, enriched in mucosae, function as both innate and adaptive components
1. Constitutive 2. Activated by “danger signals” (ie LPS,
- Summer '16