ch 14 the lymphoid system
14-1
pathogen-microorganisms that cause diseases in humans
lymphoid system- cells,tissues,and organs responsible for defending the body
the primary cells of the lymphoid system are lymphoctyes
plays a central role
immune response- provide specific defense
immunity- the ability to resist infection and disease through the activation of specific defenses
14-2
four components that includes the lymphoid system
fluid
lymphocytes
vessels
lymphoid tissues and organs
a network of lymphatic vessels often called lymphatics begins in peripheral tissues and ends at connections to veins
a fluid called lymph flows through the lymphatic vessels
lymphocytes are specialized cells that perform an array of specific functions in defending the body
lymphoid tissues are collections of loose connective tissue and lymphocytes in structures called lymphoid organs
lymphoid organs are more complex structures that contain large numbers of lymphocytes
primary functions of the lymphoid system
production,maintenance,and distribution of lymphocytes
return of fluid and solutes from peripheral tissues to the blood
distribution of hormones,nutrients, and waste products from their tissues of origin to the general circulation
lymphocytes are produced and stored within lymphoid orgns
lymphocytes respond to the presence invading pathogens,abnormal body cells,foreign proteins
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lymphocytes attempt to eliminate these threats or render them harmless through a combination of physical and chemical actions
the return of tissues fluids through the lymphoid system maintains normal blood volume and eliminates local variations in the composition of the interstitial fluid
the volume of of flow is roughly 3.6 liters per day
a break in a major lymphatic vessel can cause a rapid and potentially fatal decline in blood volume
substance unable to enter the bloodstream directly may do so by the way of lymphatic system
lymphatic vessels
lymphatic capillaries- the smallest lymphatic vessels
lymphatic vessels carry lymph from the peripheral tissues to the venous system
thoracic duct- collects lymph from the lower abdomen,pelvis,and lower limbs
right lymphatic duct- which ends at a comparable location on the right side delivers lymph from the right side of the body above the diagragm
t cells
80% of circulating lymphocytes are t cells
directly attack foreign cells
primary providers
helper t cells stimulate the activities of both t cells and b cells
suppressor t cells inhibit both t cells and b clls
t cells and suppressor t cells are also called regulatory t cells
b cells
bone marrow derived
make up 10-15% of circulating lymphocytes
b cells can differentiate into plasma cells which produce and secrete antibodies
soluble proteins that are called immunoglobilins
antibodies bind to specific chemical agents called antigens
nk cells
5-10 % of circulating lymphocytes are nk cells
these lymphocytes attack foregin cells, normal cells infected with virus and cancer cells that appear in normal tissues
their conginual monitoring of peripheral tissues are called immunological surveillance
lymphoid nodules
lymphoid nodules are masses of lymphoid tissue that are nor surrounded by a fibrous capsule
tonsils- large lymphoid nodules in the walls of the pharynx
lymphoid organs
lymph nodes- are small, oval lymphoid organs covered by a fibrous capsule and are 1-25mm
thymus-is a pink gland that lies in the mediastinum posterior to the sternum
spleen contains the largest collection of lymphoid tissues in the body
roles of the lymphoid system in body defenses
specific denfense
nonspecific defense
protect against particular threats
the bodys specific defenses produce a state of protection known as immunity or specific resistance
specific defenses are dependent on the activities of lymphocytes
they provide the body with a defensive capabiltity as nonspecific resistance
do not distinguish between one threat to another
these defense which are present at birth include physcical barriers and phagocytic cells etc
14-3
phagocytes
phagoctyes in peripheral tissues remove cellular debris and respond to invasions by forgein componds or pathogens
mircophages are the neutrophils and eosinophils that normally circulate in the blood
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macrophages large actively phagocytic cells dervided from circulating monocytes
imminological surveillance
immunological surveillance- the constant monitoring of normal tissue cells
interferons
interferons are small proteins released by activated lymphocytes macrophages and tissue cells infected with virus
cytokines chemical messengers that are released by tissue cells and coordinate local activities
the complement system
plamsa contains 11 special complement proteins that consitute the complement system
inflammation
inflammation is a locized tiisue reponse to injury
redness,swelling, heat and pain
fever
fever is the maintaince of a body temoerature greater then 99 degrees
pyrogens - ciculating proteins
14.4
types of immunity
immunity is either innate or acquired
innate immunity is genetically determined
acquired immunity is not present at birth but instead aries by active and passive
active immunity appears as a consequence of the immune response
naturally acquired active immunity normally begins to develop after birth
inducded active imuunuty antibody production is stimulated under controll condtitions
,passive immuntiy is produced by the transfer of antobodies to an indivual from other souce
naturally acquired passive immunity results when antiobdies are administered
properties of immunity
specificty a spefic defense mechanism is activated bu a spefic antigen
memory the immune system remembers antigens that its encounters
versality in the course of a normal lifetime an indiivual encounters an enormous number of antigens
tolerance although the immine response targets foreign cells and compounds its ignores normal tissue and their antigens
overview of the immune response
immune response is to inactive or destroy pathogens abnormal ceels and foregin molecules
14.5