Innate immunity

• Cerumen (Ear's wax)


  • It's also a chemical barrier
  • A substance secreted by the ears in order to kill the microbes that enter the ears to protect them
• Cerumen


  • Prevents foreign materials from entering the ear
  • Has antimicrobial and antifungal properties
• Skin


  It is characterized by a tough horny layer on its surface which acts as a barrier that is difficult to be penetrated or passed through it
• Skin


  • Contains a group of sweat glands that secrete sweat on its surface that can kill most of the microbes, because of its salinity
  • The keratinized layers (skin's outer layers) of the epidermis
  • Also called physical barrier as these cells protect all of the external surfaces of the body and form tight junctions between each other to physically prevent pathogens from entering the body
• Tears


  A fluid that protects the eyes from microbes, as it contains antimicrobial substances and enzymes which lyse the microbes
• Eyes


  • Protected by the mucous membranes which are found on the inner surfaces of the eyelids
  • Dust and dirt can carry pathogens and cause physical damage to the delicate surface of the eye
• Saliva


  A fluid that contains some toxic substances for the microbes, in addition to some enzymes that can dissolve such microbes
• Mucus in the respiratory tracts


  A viscous fluid that lines the walls of respiratory (tracts) bronchi to which the microbes and foreign bodies entering with air adhere, then the mucus with the trapped microbes and foreign bodies are expelled outside the body by the action of the beating cilia lining these tracts
• Goblet cells


  Cells specialized to secrete a fluid called mucus, found in mucous membranes
• Acidic gastric juice (secretion)


  • The epithelial cells lining the stomach produce and secrete the strong hydrochloric acid (HCI) that can kill the microbes entering with food
  • The gastric juices of the stomach (HCI) have an extremely low pH, which means that they are very acidic, serving to destroy most pathogens that enter the stomach either on our food or in the mucus that is transferred from the respiratory tract
• Sweat


  Secreted by the sweat glands on the skin surface and can kill most of the microbes due of its salinity
• Beneficial bacteria in Vagina

  Produce lactic acid, that prevents the growth of bacteria
• Chemical defenses include acidic pH levels in stomach and urine, which can kill microbes.
• Natural Immunity


  Immunity that is naturally present in the body
• Urogenital tract


  • Acid nature of urine keeps tract free from bacteria
• Vagina


  • Beneficial bacteria produce lactic acid that prevents the growth of bacteria
• Lysozyme


  An enzyme in saliva, tears, urine and sweat that kills most microbes by attacking their cell walls, allowing water in and causing the cell to burst
• Upper epidermis


  • Tough horny layer of dead cells containing the horny substance keratin
• Expulsive reflexes


  Reflexes that forcefully expel foreign substances from the body
• Coughing


  Expels material from the airways leading to the lungs
• Sneezing


  Expels material from the nasal passages
• Ear wax (cerumen)


  • Physical barrier
  • Chemical barrier
  • Waxy substance + dead cells
  • Lysozyme enzyme which lysis bacteria
• Ear wax (cerumen)


  • Physical barrier
  • Chemical barrier
• Sweat


  High concentration of salt can create an osmotic pressure gradient that can draw water out of bacteria which is one of the causes that leads to bacteria death
• Sweat glands, lacrimal glands and salivary glands


  Immune glands with external secretions (exocrine glands)
• Thymosin


  Hormone that has direct role in immunity
• Gastrin


  Hormone that has indirect role in immunity by stimulating secretion of gastric juice
• Thyroxin


  Hormone that has indirect role in immunity by keeping skin healthy