6. Lymphatic System- Organs + Immunity

thymus

bi lobed, in mediastinum, mature with thymosin

thymosin

matures T cells

organs not used

loss of function (thymus shrinks throughout life)

spleen

largest, upper left abdomen, filters blood, removes old RBC, removes pathogens from blood, activates lymphocytes

red pulp →

contains RBC

white pulp

contains WBC

viruses

simpler structure than living cells, nucleic acid + protein coat, use host cells to produce proteins and reproduce

bacteria

single, simple cells, cause many common infections (staph, strep)

innate defenses

general, present at birth, any pathogen that enters body (first line of defense)

adaptive defense

more specific, targets specific antigens, carried out by lymphocytes that recognize certain foreign molecules, ability present at birth, specific response develop with exposure

mechanical barriers

first line of defense, skin, mucous, cilia, tears, saliva, urine flow, coughing and sneezing

inflammation

local respinse to tissue injury, release of histamine, vasodilation increases blood flow, redness and warmth

increased capillary permeability

allows fluid and proteins to enter tissues → swelling

neutrophils and macrophages

move into tissue and engulf pathogens and debris

pain

chemical mediators and tissue pressure

enzymes

provide chemical barrier to pathogens

interferons

block viral replication, act against growth of tumors, stimulate phagocytosis

defensins

peptides produced by neutrophils, cripple microbes, make openings in walls to prevent function of microbes

collectins

tag pathogens so they are engulfed more easily, clump pathogens together

complement system

group of proteins in plasma and other body fluids that interact in a cascade

activation →

inflammation → attract phagocytes → enhance phagocytosis

natural killer cells

small population of lymphocytes, secrete perforins, lysing virus-infected cells or cancer cells, enhance inflammation

perforin

causes cells to explode (cancer/infected cells)

phagocytosis

phagocytes in blood vessels and tissues of the spleen, liver, or bone marrow remove particles from blood and lymph

most active phagocytic cells

neutrophils and monocytes

chemotaxis

chemicals from damaged tissues that attract phagocytes

macrophages

monocytes that leave blood

fever

virus or bacteria stimulates lymphocytes to secrete interleukin → raises thermoregulatory set point

endogenous pyrogen

interleukin (fire maker from within)

elevated body temp

inhibits microbial growth, causes liver and spleen to take up iron, makes it unavailable for bacteria to use, increases phagocytic activity and slows viral replication