Lymphatic System Flashcards
What are the three functions of the lymphatic system?
- Fluid recovery
- immunity
- lipid absorption
What percent of fluid is filtered through the lymphatic system daily?
15% 2/4L
___ in the small intestines absorb dietary lipids
Lacteals
What is lymph?
- Clear liquid, similar to plasma minus the proteins
- originates as extracellular fluid drawn into lymphatic capillaries
What four structures make up the lymphatic system?
- Lymph
- Lymphatic vessels
- Lymphatic tissues
- Lymphatic organs
What is the function of lymphatic vessels?
transport the lymph
What is the basic composition of lymphatic tissues?
aggregates of lymphocytes and macrophages
What is unique about the structure of lymphatic capillaries?
they are closed at one end
Where can lymphatic capillaries be found?
nearly all tissues of the body minus cartilage, corneas, bone and bone marrow
What is the composition of lymphatic capillary walls?
- consists of overlapping endothelial cells
- tethered by protein filaments
- They have large gaps to allow bacteria and cells to enter
- They have valves that open when pressure is to high
When lymphatic capillaries converge what do they form?
Lymphatic vessels
What are lymphatic vessels?
Large collecting vessels that are composed of three layers similar to blood vessels
What are the three layers of a large lymphatic valve?
– Tunica interna: endothelium and valves – Tunica media: elastic fibers, smooth muscle – Tunica externa: thin outer layer
When lymphatic vessels converge what do they form?
lymphatic trunks
How many lymphatic trunks or trunk pairs does they body have?
6
5 pairs and 1 single
What are the two lymphatic collecting ducts and where do they empty into in the body?
- The right Lymphatic duct empties into the right subclavian
- The thoracic duct empties into the left subclavian
What parts of the body drains into each of the lymphatic ducts?
- Right lymphatic duct: Right arm, right side of the head and thorax.
- Thoracic duct: everywhere else
What is the prominent sac that the thoracic duct begins as?
the cisterna chyli
How does lymph flow in the body?
- slower than venous blood because of no heart pump
- uses similar pumps as veins like the skeletal muscle pump
also from rhythmic contractions of the vessels
What are the 6 lymphatic cells?
NTBMDR
- Natural killer cells
- T Lymphocytes
- B Lymphocytes
- Macrophages
- Dendritic cells
- Reticular cells
What is the function of Natural killer cells?
They are large lymphocytes that attack and destroy bacteria, infected cells, transplanted tissue, and cancer
What is the function of B lymphocytes?
they activate and become plasma cells that produce antibodies
What is the function of macrophages?
- they mature from monocytes, they are large phagocytic cells that eat debris, foreign matter, bacteria, dead cells
- They are also APC’s or antigen presenting cells
What is a Antigen presenting cell? (APC)
A cell that presents antigens found to T cells which then alerts the immune system to a threat
What is the function of dendritic cells?
They are mobile APCs found in the epidermis, mucous membranes, and lymphatic organs
What is the function of reticular cells in the lymphatic system?
Cells that produce the reticular fibers that create the branched network within lymphatic organs
What are the two types of lymphatic tissues?
- Diffuse: scattered lymphocytes. in body passages open to the exterior
- Nodules(follicles): Dense masses of lymphocytes and macrophages. Nodes, tonsils, appendix
What are the primary lymphatic organs?
- Red bone marrow
- thymus
immune cells become immunocompetent here
What are the secondary lymphatic organs?
Lymph nodes, tonsils, spleen
immunocompetent cells populate these tisues
What are the two functions of lymph nodes?
- Survey lymph
- act as a site of T and B cells activation
how is the composition of lymph nodes similar to the thymus?
they both have trabeculae that divide interior into compartments
What types of vessels lead to lymph nodes?
- Several afferent lymphatic vessels
- one to three efferent lymphatic vessels in the hilim
- blood vessels
What is metastatic cancer?
- When cells from a tumor break off and end up in a new place where they then form cancer growth
- tends to effect lymph nodes and cause painless swelling
What are tonsils?
patches of lymphatic tissue located at the entrance of the pharynx
What are the three main sets of tonsils?
- Palatine tonsils back of the mouth
- lingual tonsils root of tongue
- pharyngeal tonsils (adenoids)
What are the two types of tissue found in the spleen?
– Red pulp: sinuses filled with erythrocytes
– White pulp: lymphocytes, macrophages
surrounding small branches of splenic artery
What are the functions of the spleen?
- It is the erythrocyte graveyard
- WP monitors blood for foreign antigens
- stabilizes blood volume
What are pathogens?
Agents capable of producing disease
What are the body’s three lines of defense against pathogens?
1st- Skin and Mucous membranes
2nd- innate defende mechanisms (WBC’s, inflammation, fever)
3rd-Adaptive immunity (memory of pathogen after defeat)
What are innate defenses?
defenses that guard equally against a broad range of
pathogens
What are the limitations of innate defenses?
They lack memory and are nonspecific
What are the three types of innate defenses?
- Protective proteins
- Protective cells
- Protective processes
What is adaptive immunity?
Body adapts to a pathogen and wards it off more easily upon future exposure (memory)
How do Neutrophils act against pathogens?
– Phagocytosis and destruction by fusion with lysosome
– Lysosomes degranulate, destroying several bacteria in surrounding area (neutrophil too)
How do Eosinophils act against pathogens? and where are they especially found?
found especially in mucous membranes
– Guard against eukaryotic parasites such as tapeworms and roundworms
– “Guard” against allergens (allergy-causing agents)
• By promoting action of basophils and mast cells
• Phagocytize antigen–antibody complexes
• Limit action of histamine
How do Neutrophils act against pathogens?
– Secrete chemicals that aid mobility and action of other leukocytes
• Leukotrienes: activate and attract neutrophils and eosinophils
• Histamine: a vasodilator, which increases blood flow to speeds delivery of leukocytes to the area
• Heparin: inhibits clot formation (that would impede leukocyte mobility)
– Mast cells (type of connective tissue cell similar to basophils) also secrete these substance
How do monocytes act against pathogens?
- emigrate from blood into connective tissues and
transform into macrophages
– Wandering macrophages: actively seek pathogens
• Widely distributed in loose connective tissue
– Fixed macrophages: phagocytize only pathogens that come to them
what is the Macrophage system?
all the body’s avidly phagocytic cells, except
leukocytes (so includes dendritic cells)
What type of Lymphocytes are part of innate immunity?
NK cells all others are adaptive
What are the twofamilies of antimicrobial proteins?
– Interferons
– Complement system
What are interferons?
- Proteins secreted by certin cells (many WBC’s) that are infected with a viris.
- Bind to neighbor cells and cause the synthesis of antiviral proteins
- Also calls NK cells and macrophages to eat the infected cell before it can spread
What is the complement system?
Group of 30 or more globular proteins that make contributions to
both innate immunity and adaptive immunity
• Synthesized mainly by liver and circulate in blood in inactive form
• Activated by presence of a pathogen
What are the three routes of complement activation?
- Classical pathway-Antibody dependent
- Alternative pathway-antibody independent
- Lectin pathway-antibody independent
What are the four methods of pathogen destruction brought out by the complement system?
- Inflammation
- Immune clearance
- Phagocytosis
- Cytolysis
Explain the alternative pathways of complement activation
- C3 spontaneously breaks down into C3a and C3b
- C3b binds to cells but is only active on foreign cells
- Once it binds to a foreign cell it begins a casaced of converting more C3 in C3a-b
Explain the lectin pathway of complement activation
Lectins bind to carbohydrates present on many pathogens but not on vertebrate cells
sets off the C3a-b cascade
Explain the classical pathway of complement activation
- Antibody binds to antigen forming an antibody-antigen complex
- this changes the antibody’s shape exposing complement binding sites
- C1 binds and starts C3a-b cascade
What type of mechanism of destruction does the presence of C3a cause?
inflammation
How does C3a cause inflammation?
– C3a stimulates mast cells and basophils to
secrete histamine and other inflammatory
chemicals
– C3a activates and attracts neutrophils and
macrophages
Explain the immune clearance mechanism of complement destruction
– C3b binds with Ag-Ab complexes to red blood cells – These RBCs circulate through liver and spleen where macrophages strip off and destroy the Ag–Ab complexes leaving RBCs unharmed
Explain the phagocytosis mechanism of complement destruction
– Neutrophils and have receptors for C3b
– Phagocytose what is bound to C3b receptor
– Opsonization
Explain the cytolysis mechanism of complement destruction
– C3b splits complement protein C5 – C5b, C6-8, and multiple C9 bind to foreign cell – Forms membrane attack complex (MAC) forms • Electrolytes leak out, water flows, cell ruptures
What do NK cells destroy?
– Cells coated with antibody
– Cells with surface markers representing viral infection or disease (e.g. cancer cells)
How do NK cells destroy?
- Release perforins that make a ring in target cells plasma membrane
- insert protein degrading enzymes called granzymes
- Induces apoptosis(programed cell death)
- Macrophages come to clean it all up
What is fever and what triggers it?
-an abnormal elevation of body temperature
Triggered by pyrogens
What are the two types of pyrogens and where are they found?
Endo and Exogenous
Endo-is secreted by neutrophils and macrophages
Exo- caused by a substance on foreign cell (glycolipids on bacteria)
What are the benefits of fever
– Promotes interferon activity
– Elevates metabolic rate and accelerates tissue repair
– Inhibits reproduction of bacteria and viruses
How do pyrogens work?
raise hypothalamic set point for body temperature
How do antipyretics work?
inhibit Prostaglandin E2 synthesis
• Neurons in the hypothalamus secrete prostaglandin E2 which also raises set point
What is inflammation?
local defensive response to tissue injury, including trauma and
infection
What are the purposes of inflammation?
– Limits spread of pathogens, then destroys them
– Removes debris from damaged tissue
– Initiates tissue repair
What are the four cardinal signs of inflammation?
– Redness, swelling, heat, pain
What induces inflammation?
cytokines from leukocytes or damaged
tissues
What are the three processes of inflammation?
- Mobilization of defenses
- Containment and destruction of pathogens
- Tissue cleanup and repair
Explain the process of mobilizing defenses in inflammation
- Blood flow increases
- Endothelial cells contract allowing influx of fluids, leukocytes, and plasma proteins
- Chemotaxis occurs attracting and guiding more leukocytes
The priority of inflammation is to _____
prevent pathogens from spreading
throughout body
How does inflammation contain pathogens?
- Fibrinogen that filters into the tissue forms a clot around the inflamed area
- Heparin prevents clot from forming at the site of injury creating a fluid pocket
How does inflammation destroy pathogens?
- The increased presence of neutrophils respond to and kill pathogens
- Secrete Cytokines for recruitment
- Recruted macrophages and T cells secrete colony-stimulating factor causing an increased production of WBC’s
How does inflammation cause tissue clean up and repair?
- Hyperemia allows the delivery of more nutrients
- the heat increases metabolic rate so mitosis happens faster
- pain limits use
- swelling promotes lymphatic drainage
- Monocytes clean up
- platelet dirived growth factor stimulates fibroblasts to multiply increasing collagen production
What three characteristics distinguish adaptive immunity from
innate immunity?
- Systemic effect
- specificity
- memory
What are the two types of adaptive immunity?
- Cellular
- Humoral
What is Cellular(cell-mediated) immunity?
- Lymphocytes directly attack and destroy foreign cells or diseased host cells
- rids the body of pathogens that reside inside human cells
What is humoral (antibody-mediated) immunity?
- immunity mediated by antibodies that do not directly destroy but tag it for destruction
- only works extracellular
What are the four forms of immunity?
Natural active
Natural passive
artificial active
artificial passive
What is Natural active immunity?
Production of one’s own antibodies or t-cells as a result of infection or exposure
(got sick from something)
What is artificial active immunity?
production of antibodies as a result of exposure from a vaccination
What is natural passive immunity?
– Temporary immunity that results from antibodies
produced by another person
mothers milk
What is artificial passive immunity?
– Temporary immunity that results from the injection of
immune serum (antibodies) from another person or
animal
tetanus
What is an antigen?
any molecule that triggers an immune response
What are epitopes(antigenic determinants)?
certain regions of an
antigen molecule that stimulate immune responses
What are Haptens?
too small to be antigenic in themselves
– Can trigger an immune response by combining with a host
macromolecule and creating a complex that the body recognizes as
foreign
– Subsequently, haptens alone may trigger response
– E.g. penicillin, chemicals in poison ivy, etc.
What is an antibody?
-A y shaped immunoglobulin (Ig) found in blood plasma, tissue fluids, body secretions….
What is the basic structural unit of an antibody?
The antibody monomer
What are the two regions of an antibody monomer
- Constant area-determines the mechanism of an antibody’s action
- Variable area-the unique part that detects antigens
The five classes of antibodies are based on what?
The c region of the antibody
What are the 5 classes of antibodies
IgA monomer IgD monomer IgE monomer IgG monomer IgM monomer
What is the function of a IgA monomer antibody?
- Found as a monomer in plasma
- Found as a Dimer in epithelial secretions
- prevents pathogen adherence to epithelia
- provides passive immunity to newborns
What is the function of a IgD monomer antibody?
- B cell transmembrane antigen receptor
- function in B cell activation by antigens
What is the function of a IgE monomer antibody?
- Transmembrane protein on basophils and mast cells
- Stimulate the release of histamine and chemical mediators of inflammation to attract eosinophils
What is the function of a IgG monomer antibody?
- Most abundant make up 80% of circulating antibodies
- secondary immune response and complement fixation
What is the function of a IgM pentamer?
- found in plasma and lymph
- Primary immune response, agglutination, complement fixation
What are the three categories of lymphocytes?
- NK cells-Immune surveillance
- T cells
- B-cells
Give an overview of the life of a Tcell
- Born in bone marrow
- Educated in the thymus
- Deployed to carry out immune function considered naive until first activation
Give an overview of the life of a Bcell
- Born in bone marrow
- Educated in bone marrow
- Deployed to carry out immune function considered naive until first activation
Compare how T-cells and B-cells recognize antigensgenerally
-B-cells recognize free floating antigens
T-cells can only recognize antigens when presented by another cell
How do APC present antigens?
- they encounter antigen
- eat and digest antigen
- present a piece of antigen via a MHC complex protein
- T-cells survey MHC complexes and initiate attack
What are the 4 types of T cells that function in cellular immunity
Tc-cytotoxic
Th-Helper
Tr-regulatory
Tm-Memory
What is the role of the Cytotoxic T-cell?
(T8, CD8, CD8+)
Killer T-cells
to destroy foreign cells
What is the role of the Helper T-cell?
T4, CD4, CD4+
promote Tc-cells, B-cell, and macrophage action
What is the role of the regulatory T cell?
T4, CD4, CD4+
-inhibit Tc-cell function to limit the immune response
-
What is the role of Memory T-cells?
to descend from activated T cells responsible for memory in cellular immunity
What are the three R’s of immunity aka the three stages of humoral and cellular immunity
– Recognize
– React
– Remember
How does cellular immunity recognize antigens?
T-cells survey the MHC proteins on the surface of cells and react to those that dont belong
What are the two types of MHC proteins and where are they found?
- MHC-1 –Found in all nucleated cells of the body
- MHC-2– found in APC’s
Which T-cells respond to which MHC proteins
- Tc-cells respond to MHC-1
- Th-cells responf to MHC-2
Explain the process of T-cell activation in cellular immunity
- T-cell binds with MHC protein displaying foreign epitope
- Does a double checkco-stimulation
- If co-stimulation is successful than clonal selection occurs producing clones to attack the epitope as well as memory cells
- an attack follows
How do Tc-cells attack
- Only T-cell to directly attack
- Docks onto target cell
- delivers lethal chemicals and destroys the cell in the same manner as NK cells
How do Th-cells attack?
- The attack by supporting other cells
- Activate macrophages
- supports clonal selection of B-cells and Tc-cells
What is the main cell of humoral immunity? its function?
-B-cells
-B lymphocytes of humoral immunity produce
antibodies that bind to antigens and tag them for
destruction by other means
Walk through humoral immune recognition and activation
- B-cell surface IgD antibody’s pick up antigen
- B-cell digests antigen and presents it via MHC-II
- Helper T-cell secretes interlukins to activate B-cell
- Clonal selection is triggered producing plasma cells to produce antibodies as well as memory B-cells
- Antibodies continue the attack
What are the 4 ways that antibodies attack?
- Neutralization
- Complement Fixation
- Agglutination
- Precipitation
What is Neutralization
When antibodies mask pathogenic region of antigen
What is complement fixation ?
-IgM or IgG bind to antigen and change its shape to activate the complement system
What is agglutination?
Antibodys bind to multiple sites on the cells causing them to clump together making them an easy target for phagocytic cells
What is antibody precipitation?
When antibodies bind to antigens molecules creating and antigen-antibody complex causing them to precipitate and be removed by immune clearance or phagocytosis
What is the primary immune response? define
—immune reaction brought about by the first
exposure to an antigen
- leaves one with an immune memory of
the antigen
• IgM appears first, peaks in about 10 days, soon declines
• IgG levels rise as IgM declines, but IgG titer drops to a low level within a month
What is the Secondary (anamnestic) response define
—if reexposed to the same antigen
– Plasma cells form within hours and IgG titer rises sharply and peaks in a few days
– Response is so rapid that the antigen has little chance to exert a noticeable effect
on the body and no illness results
– Low levels of IgM also secreted (then quickly decline)
– IgG remain elevated for weeks to years
• Conferring long-lasting protection
– But memory does not last as long in humoral immunity as in cellular immunity
