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The Immune System

The Immune System. The Skin. 1 st line of defense: physical barrier Oils & sweat destroy some pathogens Some cells burst Some cells shrivel. Mucus Membranes. Coat the openings of the body Nose, mouth, ears, eyes, genitals, anus Lined with cilia & sticky fluids to trap pathogens.

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The Immune System

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  1. The Immune System

  2. The Skin • 1st line of defense: physical barrier • Oils & sweat destroy some pathogens • Some cells burst • Some cells shrivel

  3. Mucus Membranes • Coat the openings of the body • Nose, mouth, ears, eyes, genitals, anus • Lined with cilia & sticky fluids to trap pathogens

  4. White Blood Cells • Job: Search & destroy • Phagocytes: surround & engulf invaders • Phagocytosis • Lymphocytes: • T cells: destroy infected body cells • B cells: Inactivate invaders

  5. Defense Proteins • Complimentary Proteins • Weaken cell membrane • Attract phagocytes • Cause microbes to stick to wall of blood vessel

  6. Defense Proteins • Antibodies • Made by B cells • Bind to cell membrane of pathogen • Prevents pathogen from binding to host cells • Causes pathogens to clump • More susceptible to phagocytes • Weakens the cell membrane • Causes them to burst

  7. Defense Proteins • Interferon • Produced by virus infected cells • Stimulates uninfected cells to create infection preventing enzymes

  8. Vaccination • Prevents infections (not a cure) • Memory cells developed without actually getting the disease • Vaccine • Contains antigens of a pathogen • Weakened pathogen is injected • Stimulates the production of memory cells • Speeds up immune response if you encounter the unweakened virus

  9. Pathogens • Defined: microorganisms that cause disease • Viruses: turn cells into virus making factories • Bacteria: prokaryotes that can release toxic chemicals • Fungi: pierce cells and absorb the nutrients • Protozoans: single cells protista (eukaryotes) • Parasites: grow and feed on a host

  10. Pathogens (contd) • Some carried by wind, water, direct contact, indirect contact… • Some carried by vectors • Vector: object that carries a pathogen • Examples: • Malaria – mosquitos carry the protozoan • Black Death – carried by flea’s of mice • West Nile Virus – carried by birds, but spread by mosquitos

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