The ability to ward off disease through body defenses
Immunity
Lack of immunity is called what
Susceptibility
First Line of Defense: Skin and Mucous Membranes
-the body’s first line of defense against infections is a physical barrier and the nonspecific chemicals of the skin and mucous membranes
First Line of Defense: Physical Factors
- the structure of intact skin and the waterproof protein keratin provide resistance to microbial invasion
- the lacrimal apparatus protects the eyes from irritating substances and microorganisms
- saliva washes microorganisms from teeth and gums
- mucus traps many microorganisms that enter the respiratory and gastrointestinal tracts, in the lower respiratory tract, the ciliary escalator moves mucus up and out
- the flow of urine moves microorganisms out of the urinary tract, and vaginal secretions move microorganisms out of the vagina
First Line of Defense: Chemical Factors
- fatty acids in sebum and earwax inhibit the growth of pathogenic bacteria
- perspiration washes microorganisms off the skin
- lysozyme is found in tears, saliva, nasal secretions, and perspiration
- the high acidity (pH 1.2-3.0) of gastric juice prevents microbial growth in the stomach
Normal Microbioata and Innate Immunity:
-normal microbiota change the environment, a process that can prevent the growth of pathogens
Second Line of Defense:
-a microbe’s penetration of the first line of defense encourages production of phagocytes, inflammation, and antimicrobial substances
Formed Elements in the Blood:
- blood consists of plasma (fluid) and formed elements (cells and platelets)
- leukocytes (white blood cells) are divided into granulocytes (neurotrophils, basophils, eosinophils) and agranulocytes
The Lymphatic System:
- the lymphatic system consists of lymph vessels, lymph nodes, and lymphoid tissue
- interstitial fluid is returned to the blood plasma via lymph vessels
Phagocytes:
- phagocytosis is the ingestion of microorganisms or particular matter by a cell
- phagocytosis is performed by phagocytes, certain types of white blood cells, or their derivatives
Actions of Phagocytes:
- enlarged monocytes become wandering macrophages and fixed macrophages
- fixed macrophages are located in selected tissues and are part of the mononuclear phagocytic system
- granulocytes, especially neutrophils, predominate during the early stages of infection, whereas monocytes predominante as the infection subsides
Mechanism of Phagocytosis:
- chemotaxis is the process by which phagocytes are attracted to microorganisms
- toll-like receptors on a phagocyte adhere to the microbial cells…adherence may be facilitated by opsonization=coating the microbe with serum proteins
- pseudopods of phagocytes engulf the microorganism and enclose it in a phagosome to complete ingestion
- many phagocytized microorganisms are killed by lysosomal enzymes and oxidizing agents
Mechanisms of Phagocytosis: Inflammation
- inflammation is a bodily response to cell damage; it is characterized by redness, pain, heat, swelling, and sometimes the loss of function
- TNF-a stimulates production of acute-phase proteins
Mechanisms of Phagocytosis: Inflammation: Vasodilation and Increased Permeability of Blood Vessels
- the release of histamine, kinins, and prostalglandins causes vasodialation and increased permeability of blood vessels
- blood clots form around an abscess to prevent dissemination of the infection
Mechanisms of Phagocytosis: Inflammation: Phagocyte Migration and Phagocytosis
-phagocytes have the ability to stick to the lining of the blood vessels (margination) and also have the ability to squeeze through blood vessels (diapedesis)
Mechanisms of Phagocytosis: Inflammation: Phagocyte Migration and Phagocytosis
- phagocytes have the ability to stick to the lining of the blood vessels (margination) and also have the ability to squeeze through blood vessels (diapedesis)
- pus is the accumulation of damaged tissue and dead microbes, granulocytes, and macrophages
Mechanisms of Phagocytosis: Inflammation: Tissue Repair
- a tissue is repaired when the stroma (supporting tissue) or parenchyma (functioning tissue) produces new cells
- stromal repair by fibroblasts produces scar tissue
Fever:
- an abnormally high body temperature produced in response to a bacterial or viral infection
- bacterial endotoxins, interleukin-1, and TNF-a can induce fever
- a chill indicates a rising body temperature; crisis (sweating) indicates that the body’s temperature is falling
Antimicrobial Substances: The Complement System
- the complement system consists of a group of serum proteins that activate one another to destroy invading microorganisms
- complement proteins are activated in a cascade
- C3 activation can result in cell lysis, inflammation, and oponization (what is this???)
- complement is activated via the classical pathway, the alternative pathway, and the lectin pathway (??)
- complement deficienies can result in an increased susceptibility to disease
- some bacteria evade destruction by complement by means of capsules, surface lipid-carbohydrate complexes, and enzymatic destruction of C5a ???
Antimicrobial Substances: Interferons
- IFNa and IFN-b induce uninfected cells to produce antiviral proteins (AVPs) that prevent viral replication
- IFN-y activates neurophils and macrophages to kill bacteria
Antimicrobial Substances: Iron-Binding Proteins
-Iron-binding proteins transport and store iron, depriving most pathogens of the available iron
Antimicrobial Substances: Antimicrobial Peptides
- antimicrobial peptides (AMPs) inhibit cell wall synthesis, form pores in plasma membranes, and destroy DNA and RNA
- antimicrobial peptides are produced by nearly all plants and animals, and bacterial resistance to AMPs has NOT yet been seen
Antimicrobial Substances: Other Factors
-other factors that influence resistance to infection include genetic resistance, age, and observing healthy protocols
