Innate Immunity

overview of the body’s defenses

 

Physical Barriers: First Line of Defense

Skin

–Epidermis ;Outer layer – thin

               Layers of tightly packed epithelial cells

              Outermost layers dead –Keratin (Protein)

                                            –Sloughs off routinely

–Dermis; Inner layer(thick)

            Connective tissue

Bacteria enter through Skin ONLY when skin is  damaged.

A section through human skin

Mucous Membranes

- Line respiratory, gastrointestinal, urogenital

- Epithelial cells with inner connective tissue

  Goblet cells; Secrete mucus (glycoproteins)

                   Prevents dessication, traps microbes, enzymes to kill microbes

-Mucus-coated nose hairs: Trap microbes

- Ciliary escalator

  Ciliated cells of Lower Respiratory Tract

  Mucus-coated dust/microbes pushed outward

  Sneezing/ Coughing speed up process

- Epiglottis; Covering over larynx: prevents food and microbes getting in

 

Other Physical/Chemical Barriers

- Tears; Lacrymal Glands: Under upper eyelid

          Constantly wash over eye; drain into lacrymal ducts

          Lysozyme (breaks peptidoglycan walls of bacterial cell walls)

•Urine; Flushing mechanism prevents colonization

          Contains uric acid, urea (makes pH ~6.5), lysozyme

•Saliva ;Salivary Glands

          Constantly washes over teeth and mouth

          Contains Lysozyme

•Peristalsis ;Movement of food by coordinated contractions

               Defecation

               Vomiting in response to microbial toxins