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The Lymphatic and Immune System
chapter 20a
102
Anatomy
Graduate
11/07/2009

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Term
Functions of Lymphatic System
Definition
Immunity
Lipid absorption
Fluid recovery
(absorbs plasma proteins and fluid (2 to 4 L/day) from tissues and returns it to the bloodstream)
Term
Lymph
Definition
clear, colorless fluid, similar to plasma but much less protein
Term
Lymphatic capillaries
Definition
tethered to surrounding tissue by protein filaments
endothelial cells loosely overlapped
closed at one end
creates valve-like flaps that open when interstitial fluid pressure is high, and close when it is low
Term
Collecting vessels
Definition
course through many lymph nodes
Term
Lymphatic trunks
Definition
drain major portions of body
Term
right lymphatic duct
Definition
receives lymph from R arm, R side of head and thorax; empties into R subclavian vein
Term
thoracic duct
Definition
larger and longer, begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, L arm, L side of head, neck and thorax; empties into L subclavian vein
Term
Lymph Flow
Definition
Moved along by rhythmic contractions of lymphatic vessels
flows at low pressure and speed
aided by skeletal muscle pump
Valves prevent backward flow
flowing blood in subclavian veins, draws lymph into it
Term
T lymphocytes
Definition
mature in thymus
cell to cell interactions destroy pathogens throughout the body
Term
B lymphocytes
Definition
activation causes proliferation and differentiation into plasma cells that produce antibodies
Term
Natural killer (NK) cells
Definition
responsible for immune surveillance by destruction of foreign cells
Term
Antigen Presenting Cells
Definition
macrophages (from monocytes)
dendritic cells (in epidermis, mucous membranes and lymphatic organs)
reticular cells (also contribute to stroma of lymph organs)
Term
Diffuse lymphatic tissue
Definition
lymphocytes in mucous membranes and connective tissue (CT) of many organs
Mucosa-Associated Lymphatic Tissue
Term
Mucosa-Associated Lymphatic Tissue
Definition
MALT): prevalent in passages open to exterior
Term
Lymphatic nodules
Definition
dense oval masses of lymphocytes, congregate in response to pathogens
Peyer patches
Term
Peyer patches
Definition
more permanent congregation, clusters found at junction of small to large intestine
Term
Primary lymphatic organs
Definition
site where T and B cells become immunocompetent
red bone marrow and thymus
Term
Primary lymphatic organs
Definition
site where T and B cells become immunocompetent
red bone marrow and thymus
Term
Secondary lymphatic organs
Definition
immunocompetent cells populate these tissues
lymph nodes, tonsils, and spleen
Term
Lymph nodes
Definition
- only organs that filter lymph
the capsule arises trabeculae, which divides node into compartments containing stroma (reticular ) and parenchyma (lymphocytes and Antigen Presenting Cells) subdivided into cortex (lymphatic nodules) and medulla
Term
Lymphadenopathy
Definition
all lymph node diseases
Term
Lymphadenitis
Definition
swollen, painful node responding to foreign antigen
Term
Thymus
Definition
Reticular epithelial cells
form blood thymus barrier in cortex
isolates developing T lymphocytes from foreign antigens
secretes hormones (thymopoietin, thymulin and thymosins)
to promote development and action of T lymphocytes
large in fetus
Term
Spleen
Definition
red pulp/white pulp
functions:
blood production in fetus
blood reservoir
RBC disposal
immune reactions: filters blood, quick to detect antigens
Term
red pulp
Definition
sinuses filled with erythrocytes
spleen
Term
white pulp
Definition
lymphocytes, macrophages; surrounds small branches of splenic artery
spleen
Term
Innate Immunity
Definition
Nonspecific defenses which are broadly effective, no prior exposure necessary

first line of defense
external barriers

second line of defense
phagocytic cells, antimicrobial proteins, inflammation and fever
Term
Adaptive Immunity
Definition
Specific defenses which result from prior exposure, protects against only a particular pathogen
third line of defense
“the immune system”
Term
First line of defense:skin
Definition
toughness of keratin
dry and nutrient-poor
defensins: peptides, from neutrophils attack microbes
lactic acid (acid mantle) is a component of perspiration
Term
First line of defense: mucous membranes
Definition
stickiness of mucus
lysozyme: enzyme destroys bacterial cell walls
Term
First line of defense: Subepithelial areolar tissue
Definition
tissue gel: viscous barrier of hyaluronic acid
hyaluronidase: enzyme used by pathogens
to spread
Term
Neutrophils
Definition
Phagocytize and kill bacteria
degranulation
lysosomes discharge into tissue fluid
respiratory burst
toxic chemicals are created (O2.-, H2O2, HClO)
Term
Eosinophils
Definition
Phagocytize antigen-antibody complexes
Antiparasitic effects (tapeworms, roundworms)
Promote action of basophils, mast cells
Enzymes block excess inflammation, limit action of histamine (allergic responses)
Term
Basophils
Definition
Aid mobility and action of WBC’s by secretion of two chemicals
histamine+heparin
Term
histamine
Definition
(vasodilator)
increases blood flow to infected tissue which delivers leukocytes to the area
EOSINOPHILS
Term
heparin
Definition
(anticoagulant)
prevents immobilization of phagocytes
Term
Natural Killer (NK) Cells
Definition
Large Granular Lymphocytes (LGL’s)
not lymphocytes though
Release Perforins which form a hole
in target cell and release cytotoxic granules
called Granzymes into the cell and kills it
Term
Interferons
Definition
Secreted by certain cells invaded by viruses
diffuse to neighboring cells and stimulate them to produce antiviral proteins
activate natural killer cells, T cells and macrophages
Term
Complement System
Definition
enhanced inflammation
phagocytosis
promoted by opsonization
cytolysis
membrane attack complex forms on target cell
immune clearance
RBCs carry Ag-Ab complexes to macrophages in liver and spleen
Term
classical pathway
(complment system)
Definition
requires antibody; specific immunity
Term
alternate pathway
(complement system)
Definition
nonspecific immunity
Term
lectin pathway (complement system)
Definition
nonspecific immunity
Term
Lectin Pathway
Definition
causes cytolosis
Term
Membrane Attack Complex
Definition
Complement proteins form ring in plasma membrane of target cell causing cytolysis
Term
Apoptosis
Definition
DNA is degraded and packaged and cell dies
also known as “programmed cell death” or “cellular suicide”
Term
Inflammation
Definition
limits spread of pathogens, then destroys them
removes debris
initiates tissue repair
Term
Cytokines
Definition
small proteins regulate inflammation and immunity; include
interferons, interleukins, tumor necrosis factor, and chemotactic factors
Term
Inflamation Signs
Definition
redness (erythema) caused by hyperemia ( blood flow)
swelling (edema) caused by  capillary permeability and filtration
heat caused by hyperemia
pain caused by inflammatory chemicals (bradykinin, prostaglandins) secreted by damaged cells, pressure on nerves
Term
margination (leukocyte deployment)
Definition
selectins cause leukocytes to adhere to blood vessel walls
Term
diapedesis (emigration)
(leukocyte deployment)
Definition
leukocytes squeeze between endothelial cells into tissue space
Term
Fever
Definition
promotes interferon activity
accelerating metabolic rate and tissue repair
inhibiting pathogen reproduction
105F may cause delirium, 111F- 115F, coma-death
Term
interleukin 1
Definition
cytokine
pyrogen
secreted by macrophages, stimulates anterior hypothalamus to secrete PGE which resets body thermostat higher
Term
Adaptive Immunity
Definition
Specificity Memory
Cellular immunity
Humoral defense
Term
Cellular immunity
Definition
(cell-mediated) via T-Cells. Attack fungi, parasites, viruses, cancer cells and foreign tissue.
Term
Humoral defense
Definition
(antibody-mediated) with B-cells. B-cells become plasma cells, leave the nodes and produce antibodies (Ig’s). Attack bacteria and viruses.
Term
Natural active immunity
Definition
(produces memory cells)
production of one’s own antibodies or T cells as a result of infection or natural exposure to antigen
Term
Artificial active immunity
Definition
(produces memory cells)
production of one’s own antibodies or T cells as a result of a vaccination
Term
Natural passive immunity
Definition
(through placenta, milk)
temporary, fetus acquires antibodies from mother
Term
Artificial passive immunity
Definition
(snakebite, rabies, tetanus)
temporary, injection of immune serum (antibodies)
Term
Antigens
Definition
Trigger an immune response
proteins, polysaccharides, glycoproteins, glycolipids
Epitopes
Term
Epitopes
Definition
(antigenic determinants)
stimulate immune responses
Term
Haptens
Definition
too small, host macromolecule must bind to them to stimulate initial immune response
Term
Specific immunity
Definition
depends on activities of two general classes of lymphocytes
B-Cells
T-Cells
Term
Life Cycle of T cells
Definition
Arise from stem cells in red bone marrow
Mature in thymus
naïve T cells colonize lymphatic tissue and organs
Term
thymosins
Definition
stimulate maturing T cells to produce antigen receptors
Term
T-Cell Maturation in Thymus
Definition
thymic hormone secreted by reticular epithelial (RE) cells stimulate them to develop surface antigen receptors.

“tested” to see if they recognize self antigens and MHC antigens
Term
Negative Selection
Definition
T-cells that recognize either self or MHC antigens are eliminated

clonal deletion (destruction) or anergy (they remain alive but are non responsive).
Term
Positive Selection
Definition
T-cells that have “passed” (only 2% graduate!) the test now move to the thymic medulla

and form clones of T-cells with varying antigenic specificity.
Term
B Lymphocytes (B cells)
Definition
development (Bone marrow)
other fetal stem cells remain in bone marrow
B cells should not react to self antigens
or suffer clonal deletion or anergy
Term
Antigen-Presenting Cells (APCs)
Definition
B cells, macrophages, reticular cells and dendritic cells (special type of macrophage) function as APC’s and display antigens which are combined with MHC proteins on their surface to T cells

When an APC encounters an antigen, it internalizes it by endocytosis, digests it into molecular fragments and displays the relevant fragments (epitopes) in the grooves of the MHC proteins. This is called ‘Antigen Processing”
Term
major histocompatability complex
Definition
proteins which are expressed on antigen presenting cells (APC’s

MHC proteins are structurally unique to every person and act as cell “ID” tags
Term
Interleukins
Definition
Chemical messengers between leukocytes
Used by lymphocytes and APCs to communicate
Term
Cellular Immunity
Definition
T cells attack diseased host tissues or cells invaded by microbes and can “remember” these antigens and prevent from future attack.
Term
Cytotoxic T cells
Definition
(TC cells) carry out attack
Term
Helper T cells
Definition
(TH cells): help promote TC cell and B cell action and nonspecific defense mechanisms
Term
Memory TM
Definition
provide immunity from future exposure to antigen
Term
TC Cells Vs TH Cells
Definition
Tc- MHC-1
Th-MHC-2
Term
TC Cell Recognition
Definition
MHC-I proteins
found on nearly all nucleated body cells
display peptides produced by host cells
Term
TC cell activation
Definition
binding of cytotoxic T cells (CD8 cells) to abnormal peptides on MHC-I and
costimulation via a cytokine
triggers clonal selection: clone of identical T cells against cells with same epitope
Term
TH cell Recognition
Definition
role of MHC-II proteins
found only on antigen presenting cells
display only foreign antigens
stimulate helper T cells (CD4 cells)
Term
Attack Phase: Role of Helper T Cells
Definition
Secretes interleukins
attract neutrophils, NK cells, macrophages
stimulate phagocytosis
stimulate T and B cell mitosis and maturation
Term
Attack Phase: Cytotoxic T Cells
Definition
Only T cells directly attack enemy cells
docks on cell with antigen-MHC-I protein complex
releases perforin, granzymes - kills target cell
interferons - decrease viral replication and activates macrophages
tumor necrosis factor: kills cancer cells
Term
Humoral Immunity (B-Cells)
Definition
B cell receptors bind antigen, take in and digest antigen then display epitopes on its MHC-II protein
After costimulation by TH cell, divide repeatedly, differentiate into plasma cells, produce antibodies specific to that antigen
‘tag it’ for destruction
some B cells differentiate into memory cells
Term
Somatic recombination
Definition
DNA segments shuffled and form new combinations of base sequences to produce antibody genes
Term
Somatic hypermutation
Definition
B cells in lymph nodules rapidly mutate creating new sequences
Term
IgA
Definition
: monomer in plasma; dimer in mucus, saliva, tears, milk, intestinal secretions, prevents adherence to epithelia
Term
IgD
Definition
monomer; B cell membrane antigen receptor
Term
IgE
Definition
monomer; on mast cells; stimulates release of histamines, attracts eosinophils; immediate hypersensitivity reactions
Term
IgG
Definition
monomer; 80% circulating, crosses placenta to fetus, 2 immune response, complement fixation
Term
IgM
Definition
: pentamer, 10% in plasma, 1 immune response, agglutination, complement fixation
Term
Neutralization
(humural immunity)
Definition
antibodies mask pathogenic region of antigen
Term
Complement fixation
(humural immunity)
Definition
antigen binds to IgM or IgG, antibody changes shape, initiates complement binding; primary defense against foreign cells, bacteria
Term
Agglutination
Definition
antibody has 2-10 binding sites; binds to multiple enemy cells immobilizing them
Term
Precipitation
(humoral immunity)
Definition
antibody binds antigen molecules (not cells); creates antigen-antibody complex that precipitates, phagocytized by eosinophil
Term
Type I (acute reaction) hypdersensitivity
Definition
Antibody mediated (IgE), (food allergies, asthma, anaphylaxis)
Term
Type II (antibody-dependent cytotoxic)hypersensitivity
Definition
Antibody mediated (IgG, IgM), subacute (blood transfusion reactions, some drug reactions)
binds to antigens on cells; complement activation and lyses or opsonization
may bind to cell surface receptors and either interferes with function or over-stimulate cell
Term
Type III (immune complex) hypersensitivity
Definition
Antibody mediated (IgG, IgM), subacute
(autoimmune acute glomerulonephritis and lupus

IgG or IgM form widespread antigen-antibody complexes
Complexes precipitate and trigger intense inflammation
involved in acute glomerulonephritis and in systemic lupus erythematosus
Term
Type IV (delayed) cell mediated, delayed (12 to 72 hr), hypersensitivity
Definition
), (allergies to haptens in cosmetics, poision ivy, graft rejection, tuberculosis skin test, insulin-dependent diabetes)

APC’s in lymph nodes display antigens to helper T cells, which secrete interferon and cytokines that activate cytotoxic T cells and macrophages
Cosmetic and poison ivy allergies - haptens
TB skin test
Term
Anaphylaxis
Definition
occurs in sensitized people
allergen caps IgE on mast cells, basophils
release inflammatory chemicals
Term
Asthma
Definition
most common chronic illness in children
inhaled allergens, histamines, bronchiole constriction
Term
Anaphylactic shock
Definition
bronchiole constriction, dyspnea, vasodilation, shock, death; treatment- epinephrine
Term
HIV
Definition
invades helper T cells, macrophages and dendritic cells by “tricking” them to internalize viruses by receptor mediated endocytosis

reverse transcriptase (retrovirus), uses viral RNA as template to synthesize DNA, new DNA inserted into host cell DNA, may be dormant for months to years
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