And infectious diseases Immune System And infectious diseases

Immune System The network of cells, tissues, and organs that work together to protect the body against infectious invaders. The organs involved in the immune system are called the lymphatic system and consist of: Thymus Spleen Bone Marrow Lymph Nodes These are important parts of the immune system because they produce or store leukocytes

Leukocytes Leukocytes circulate through the blood and lymphatic system and there are two types: Phagocytes Lymphocytes Cells that engulf and break down the invading organism Most common is neutrophils, which fight bacteria cells that allow the body to remember and recognize previous invaders and help the body destroy them B-cells and T-cells find organisms identified by antibodies and destroys them

Lymphocyte Response When foreign organisms (antigens) are recognized by the body B-cells produce antibodies Antibodies are proteins that are developed to lock onto specific antigens These antibodies will be present in your body for life, so the next time that antigen enters your body it is destroyed very quickly That is how immunizations work, they introduce a weakened antigen into your body, so your body can produce antibodies in case a stronger antigen returns Antibodies cannot destroy these antigens on their own, the T-cells destroy the antigens

Types of Immunity Humans have three different types of immunity: Innate – immunity you are born with Adaptive – immunity that develops throughout our lives Passive – immunity that is borrowed from another person or source

Innate Immunity This includes lots of our external barriers that prevent antigens from ever entering our bodies Our skin prevent germs from entering our blood stream If there is a break in the skin, it will try to heal and blood flows outward preventing the infection from getting inside Our breathing passages are covered in hairs and mucus that are meant to trap foreign organisms and expel them from our bodies Organisms that enter through our mouth will either be killed by the chemicals in our saliva or the acid in our stomach

Adaptive Immunity Adaptive immunity includes the antibodies we develop by being exposed to different diseases throughout our lives and the vaccinations we receive

Passive Immunity Sometimes we can borrow immunity from another source, but this does not usually last for very long The most common example of this is when babies get antibodies from the mother’s breast milk, which is one reason breast feeding is beneficial for babies Milk really does a body good (breast milk)

Inflammatory Response Inflammatory response is when fluid and white blood cells leak out of the blood vessels and into the tissues. The white blood cells fight the pathogens During an inflammatory response, the blood vessel get wider to increase the flow of blood to that area Because of the increase blood flow and the fluid leaking into the tissue, an inflamed area will look red and swollen. Also, the inflamed area will feel warn to the touch. In some cases, the inflammatory response will result in you having a temperature. This high temperature keeps pathogens from reproducing.

Infectious Diseases a disease that can be passed from one organism to another (called antigens or pathogens) When you have an infectious disease, a pathogen has gotten into your body and harmed it Pathogens make you sick by damaging individual cells There are four major groups of pathogens

Bacteria Bacteria are single cell organisms Bacteria are classified as PROKARYOTES Most bacteria cannot make their own food; they have to break down, or decompose, other living things to obtain their energy Most bacteria do not cause diseases Bacteria are almost everywhere: air, food, water, soil. Example: Strep throat

Viruses Virus – a nonliving particle consisting of a core of hereditary material surrounded by a protein coat. Viruses can reproduce ONLY inside a living cell. Examples: Flu, common cold

Fungi Most fungi are multicellular Fungi obtain food by secreting enzymes onto the dead material outside of their bodies (external digestion). The fungi then absorb the nutrients into their cells. Organisms that feed this way are called SAPROPHYTES Example: Athlete’s foot

Protists One cell organisms (unicellular) that have organelles Example: Malaria

Man-Made Defenses PASTERUIZATION – a heating process that is used today to kill microorganisms in food products such as milk ANTIBIOTICS – a chemical that is used to kill bacteria or slow their growth without harming your body cells. Unfortunately, there is no way to cure viral diseases.

Spread of Disease PERSON-TO-PERSON TRANSFER CONTAMINATED OBJECTS Diseases can be transferred by direct contact such as kissing and shaking hands Diseases can be transferred by indirect contact such as sneezing and coughing CONTAMINATED OBJECTS Food and water can become contaminated You can get ill by using contaminated objects such as towels and silverware ANIMAL BITES An infected animal can pass on pathogens through their bite Examples: rabies (dog, raccoon), Lyme disease (tick), malaria (mosquitoes in tropical areas) PATHOGENS FROM THE ENVIRONMENT Some pathogens live naturally in the soil and water Example: tetanus, botulism (causes food poisoning)

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