Anatomy and Physiology - The Immune System and Other Body Defenses - Quick Guides | Anatomy and Physiology

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Study GuideAnatomy and Physiology–The Immune System andOther Body Defenses1.Nonspecific BarriersYour body has a “first line of defense” that worksall the time, even before your immune system startsmaking a specific response.This first line of defense is callednonspecific defensebecause it fightsmany kinds of invaders inthe same way, not one specific germ.The main nonspecific barriers are:skinmucous membranesThese protect the body from harmful invaders entering through:•breaks in the skin•body openings (like the mouth, nose, and other passages)How the First Line of Defense Protects You1. Skin: Strong Physical + Chemical BarrierSkin works like a tough protective wall.It is aphysical barrier, and it is also ahostile environmentfor microbes because it is coated withsecretions:•oily secretionsfromsebaceous glands•acidic secretionsfromsweat glandsThe skin surface has an acidic pH of about3 to 5, which prevents many microbes from growing.

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Study Guide2. Antimicrobial Proteins on Mucous MembranesMucous membranes produce secretions that contain antimicrobial substances.For example:•lysozymeLysozyme helps protect you by:•breaking down bacterial cell wallsLysozyme is found in:•saliva•tears•other mucous membrane secretions3. Cilia: Sweeping Invaders AwayIn the respiratory system, tiny hair-like structures called:cilialine the respiratory tubes.Their job is to:•sweep dust, microbes, and other invaders away from the lungsThis helps prevent infection in deeper lung tissues.4. Gastric Juices Kill MicrobesThe stomach provides another strong defense.gastric juicesdestroy many microbes using:•hydrochloric acid•digestiveenzymesSo most microbes that enter through food do not survive the stomach.

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Study Guide5. Symbiotic Bacteria Protect UsYour body also has “helpful” bacteria called:symbiotic bacteriaThese live in areas like:•thedigestive tract•thevaginaThey help protect you because they:•outcompete harmful organismsmeaning they take up space and nutrients so dangerous microbes cannot grow easily.2.Quiz: Nonspecific Barriers1. QuestionWhich of the following would be considered a nonspecific barrier?Answer Choices• skin• fever• NK cellsCorrect AnswerskinWhy This Is CorrectTheskinis aphysical barrierthat blocks pathogens from entering the body.This is part of the body’sfirst line of defense (nonspecific defense).

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Study Guide2. QuestionWhich of the following is involved with specific defenses?Answer Choices• lysozymes• complement protein• major histocompatibility complexCorrect Answermajor histocompatibility complexWhy This Is CorrectThemajor histocompatibility complex (MHC)helps the immune system recognize antigens and isessential forspecific (adaptive) immunity, especially T-cell responses.3.Nonspecific DefensesThesecond line of defenseincludes immune responses that fight invadersafter they enter thebody.These defenses are callednonspecificbecause they:attack many kinds of pathogens the same waydo not target one specific germ only3.1Key Parts of the Second Line of Defense1. Phagocytes (Engulf and Destroy Invaders)Phagocytesare white blood cells (leukocytes) that destroy pathogens by:phagocytosis(engulfing and digesting them)Main phagocytes include:

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Study Guide•neutrophils•monocytes•eosinophilsMonocytes can grow larger and become powerful phagocytes called:macrophagesMacrophages are important because they clean up both:•pathogens•damaged cells and debris2. Natural Killer (NK) CellsNatural killer cells (NK cells)are a type of:lymphocyte (white blood cell that matures in lymphoid tissues)Their job is to kill:•pathogen-infected body cells•abnormal body cells(such as tumors)So NK cells are like “security guards” that eliminate dangerous cells.3. Complement ProteinsComplement proteinsare a group of about:20 proteinsThey are called “complement” because theysupport and strengthenthe body’s defense reactions.They help in two main ways:•attract phagocytes to foreign cells•destroy foreign cells by causingcell lysis(breaking open the cell)

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Study Guide4. Interferons (IFNs)Interferons (IFNs)are chemicals released by cells that have been:invaded by virusesInterferons help protect nearby cells by causing them to produce proteins that:defend against virusesSome interferons (likegamma-IFN) also:•increase the activity of macrophages•increase the activity of NK cellsSo interferons not only fight viruses directly but also boost other defenders.3.2The Inflammatory ResponseTheinflammatory responseis a series of nonspecific body reactions that happen when pathogensenter tissues or when tissue damage occurs.Common signs of inflammation include:•redness•swelling•heat•painsometimes loss of function (the area may be disabled)Example: If the skin is damaged and bacteria or toxins enter, inflammation begins.Steps of the Inflammatory Response (Easy Order)1. Chemical AlarmWhen an injury happens, the body releases “alarm chemicals.”These signals come from:injured cells

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Study Guidenearby circulating cellsImportant alarm chemicals include:•histamine(mostly secreted by basophils—WBCs found in connective tissue)•kinins•prostaglandins (PGs)•complement proteinsThese chemicals alert the immune system and start defense actions.2. Vasodilation (More Blood Flow to the Area)Histamine and other chemicals cause:vasodilation(blood vessels widen)This increases blood flow to the injured area, causing:•redness•increased local temperature (heat)The higher temperature helps because it:•stimulates white blood cells•creates an environment that is less friendly to pathogens3. Increased Vascular PermeabilityAlarm chemicals also increase:vascular permeabilityThat means blood vessels become “leakier,” allowing important things to move into the injured tissuefaster, such as:•white blood cells•clotting factors•body fluidsThis results in:edema (swelling)

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Study GuideSwelling can cause pain because:•it presses on nearby nerve endings•nerves may also react to toxins and chemicals like kinins and prostaglandinsImportant note:Aspirin reduces painbecause it inhibits the production ofprostaglandins.4. Phagocytes Arrive and Destroy the ThreatNext, phagocytes move to the injury site and engulf:•pathogens•damaged cellsThey find the injured area using:chemotaxis(movement toward chemical gradients created by alarm chemicals)5. Complement Proteins AssistComplement proteins help in two ways:help phagocytes engulf foreign cellsstimulate basophils to release more histamineSo they strengthen the whole inflammatory response.3.3Fever (Whole-Body Response)Afeveris a body-wide response to infection where body temperature rises.Higher temperature helps because it:•increases cellular metabolism(faster repair)•increases the effects of alarm chemicals•creates a hostile environment for bacteria

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Study GuideHowever, if fever becomes too high, it can be dangerous because:•it may reduce the activity of enzymes needed for metabolism•pushing the body further out of homeostasis4.Quiz: Nonspecific Defenses1. QuestionInterferons are substances released by some cells to fight __________.Answer Choices• bacteria• viruses• symbiotic pathogensCorrect AnswervirusesWhy This Is CorrectInterferonsare released when cells are infected byviruses.They warn nearby cells and help slow down viral spread.2. QuestionVasodilation helps bring more WBCs to an infected site. What chemical causes vessels to dilate?Answer Choices• histamine• prostaglandin• complement proteins

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Study GuideCorrect AnswerhistamineWhy This Is CorrectHistaminecauses blood vessels todilate and become more permeable, allowing more immunecells to reach the damaged area.3. QuestionThe inflammatory response is part of the __________.Answer Choices• specific defense• nonspecific defense• nonspecific barrierCorrect Answernonspecific defenseWhy This Is CorrectInflammation is part of thesecond line of defense, meaning it isnonspecificand responds to manytypes of injury or infection.4. QuestionMolecules that attract phagocytes to foreign cells are called __________.Answer Choices• interferons• complement proteins• major histocompatibility complex

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