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109 Cards in this Set
- Front
- Back
What is the purpose of the lymphoid system |
It responds immunologically to invading foreign substances |
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What is the main function of the lymphoid system |
To protect organisms against invading pathogens or antigens or antigens ( bacteria, viruses, parasites) |
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Wen does an immune response occur |
When organissm detects pathogens, able to enter organism at any point |
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What is the minor function of lymphatic system |
1) Collects excess interstitial fluid into lymphatic capillaries
2) transports absorbed lipids from small intestine |
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What percent of the blood does lyphocytes make up |
20 to 30% |
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What percent of lymphocytes in the blood are small lymphocytes |
90% |
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Where does mammalian stem cells differentiate |
in the bone marrow |
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What cells that differentiate in the bone cells turn into |
several kinds of blood cells |
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Where do lymphocytes originate from |
During the process from a common lymphoid progenitor before differentiating into their distinct lymphocyte types. |
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What is the ormation of lymphocytes called |
lymphopoiesis |
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B lymphocytes |
Mature from B cells in the bone Marrow |
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T cells |
T cells migrate to and mature in a distinct organ, the thymus |
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What occurs with the lymphoctes after maturation |
They enter the circulation and go to the peripheral lymphoid organs (e.g the spleen and lymph nodes )Where they survey for invading pathogens and/ or tumor cells
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What are the four types of T cells |
1) Hepler T cells 2) Cytoxic T cells 3) Memory T cells 4) Suppressor T cells |
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Helper T ells |
Assist other lymphocytes by secreting immune chemicals called cytokines (interleukins). Plasma cells then produce antibodies |
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Cytokines |
Protein hormones that stimulate proliferation, differentiation and maturation of B cells into plasma cells. |
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Cytotoxic T cells |
Recognize antigenically different cells such as virus-infected cells, malignant cells or foreign cells, and estroy them. |
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How are cytoxic T cells actiated |
When they combine with antigen that react with their receptors |
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Memory T cells |
Long living progeny of T cells. Respond rapidly to same antigens if they reappear in the body and stimulate production of cytotoxic T Conterpart of memory B cells |
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Suppresor T cells |
Decrease or inhibit the function of helper T cells and cytotoxic T cells. Modulate immune response |
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What happens to the b cells in the bone marrow |
They mature and become immunocompetent |
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What occurs after maturation to the B cells |
Blood carries B cells to the lymph nodes ,spleen and connective tissue |
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How do B cells work |
They recognize antigen with with antigen receptors on their membrane surface |
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What occurs after the B cells bind to specific antigen |
Immunocompetent B cells acrivate |
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What is the response of B cells to an antigen |
Antigen-presenting cell ( eg. macrophage) presents the antigen to a B cell. A helper T cell secretes cytokine inducing proliferation and differentiation of antigen -activated B cell. |
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What does activated B cells become |
Plasma cells |
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Plasma cells |
Secrete large amounts of antibodies specific to the antigen that triggered plasma cell formation |
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What is the job of antibodies |
To react with antigens and initiate a process that will destroy the foreign substance |
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What happens to B cells that do not secrete antibodies |
They become memory B cells. These cells produe a more rapid immunologic response if the same antigen reappears |
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What are the four stages of the Humoral immune response |
1) B cells are exposed to antigen
2) Proliferation and diferentiation of B cells into plasma cells 3) Plasma cells secrete specific antibodies into blood and lymph 4) Antibodies bind to, inactivate and destroy specific foreign substance of the antigen |
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What does the activation and proliferation of B cells require to a specific antigen require |
Helper T cells taht respond to the same antigen and will secrete cytokines |
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What is the basis of humoral response |
Presence of B cells, plasma cells and antibodies in blood and lymph are the basis of humoral immune response |
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What encounters the innate immune system |
Microorganisms or toxins that successfully enter an organisms |
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What usually innitiates the immune response |
It is usually triggered when microbes are identified by pattern recognition receptors ( PRR). |
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How do pattern recognition receptors recognize |
PRRs recognize 1) components that are conserved among broad groups of microorganisms 2) or when damaged ,injured or stressed cells send out alarm signals, many of which are recognized by the same receptors as those that recognize pathogens |
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Describe Innate immune defenses |
1) They are non-specific: these systems respond to pathogens in a generic way 2) This system does not confer long-lasting immunit against a pathogen 3) Innate immune system is the dominate system of host defense in most organisms |
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What are lymph nodes |
Small, flattened oval or bean shaped organs, located in the course of the collecting lymph vessel |
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What is the size of a lymph node |
From a few mm to more than 2 cm |
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How are the capsule and trabeculae of lymph nodes formed |
By connective tissue |
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Describe capsule in reference to trabeculae |
The connective tissue capsule surrounds lymph node and sends trabeculae into its interior |
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What are the 2 major parts of the lymph node |
1) Outer cortex 2) Inner medulla |
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What forms the cortex |
The reticular fibers and aggregations of lymphocytes |
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What are the lighter staining central areas of the lymphoid nodules |
germinal centers |
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What is the germinal center |
the area of lymphocyte poliferation |
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What makes up the medulla |
medulalry cords and medullary sinuses |
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medularry cors |
network of reticular fibers filled with plasma cells, macrophages and lymphocytes |
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What separates the medullary cords |
Medullary sinuses |
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What are medullary sinuses |
capillary like channels |
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What is lymph entering the lymph node vi |
afferent lymphatic vessels |
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Where do afferent lymphatic vessels penetrate the capsule surface |
These penetrate the capsule on the convex surface |
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What does the afferent lympgatic vessels composed of |
Valves |
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Where do the valves empty |
that empty into the subscapular ( marginal) sinus |
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Where is lymph carried once reaching the node and entering via the afferent lymphatic vessels that penetrate the capsule on the cortex surface |
The lymph flows through trabecular ( cortical) sinuses then medullary sinuses |
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What is the concavity of the lymph node called |
a hilus |
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What is in the hilus of the lymph node |
Nerve, blood vessels and veins |
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Where does lymph exist |
Opposite side via efferent lymphatic vessels in the hilus |
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Describe the circulation of lymph |
1) enters through the lymph node via the afferent lymphatic vessels which peentrate the capsule on the convex surface 2) Afferent lymphatic vessels have valves that empty in to the subscapula sinuses 3) lymph flows through the trabecualr (cortical sinuses) then medullary sinuses 4) Lymph exits lymph node on the opposite side via efferent lymphatic vessels in the hilus |
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What are the functions of lymph nodes |
Lymph filtration and phagocytosis of bacteria or foreign substances from the lymph |
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Where are lymph nodes located |
along the path of lymphatic vessels |
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Where are lymph nodes more prominent |
In inguinal and axillary regions |
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What is the job of macrophages |
1) To destroy bacteria trapped in retinacular net 2) To producte, recirculate B cells and T cells - T cells proliferate - B cells turn into plasma cells |
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What is located in lymph leaving the lymph node
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Antibodies or the whole body |
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Where are B cells located |
In lymphatic nodules |
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Where are T clls located |
Deep cortical/paracortical regions |
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Lymph nodes: |
sites of antigen recognition and antigen activation of B cells |
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By what do lymphocytes leave the node and where is the lymph going
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By efferent lymph vessels to return to the blood stream |
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What is the thymus |
A soft lobulated organ |
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Where is the thymus located |
In the upper anterior mediastinum |
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When is the thymus most active |
During childhood |
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What happens to the thymus in adults |
Involuation ( it becomes filled with adipose tissue |
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What is the thymus surrounded by |
Connective tissue capsules |
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What is the thymus made up of |
A dark stained cortex with a network of interconnecting spaces |
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What is located in the spaces |
They are colonized by immature lymphocytes migrating from bone marrow |
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What occurs in the thymus |
The maturation and differentiation of T lymphocytes in the thymus |
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What occurs in the lighter- stained medulla of the thymus, |
the epithelial cells form a network containing fewer lymphocytes and whorls of epithelial cells from thymic (Hassall's) corpuscles |
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What is the job of trabeculae in the thymus |
-Trabeculae extend into thymus and divide it intonumerous incomplete lobules |
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What does eaxh lobule consists of |
-dark-stained outer cortex and light-staining inner medulla |
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How do blood vessels get into the thymus |
1) capsule 2) trabeculae |
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Describe the histology changes of the thymus with age |
-greatest development shortly after birth. Thymus begins to regress and degenerate attime of puberty. Consequently, lymphocyte productiondecreases and the number of Hassall’s corpuscles increases with time -Progressively, parenchyma replaced by loose connectivetissue and adipose tissue |
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What is the spleen |
A large lymphoid organ with rich blood supply. Like the lymph nod it is a discriminatory filter |
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What is the difference between spleen and lymph nodes |
The slpleen is inserted into the blood stream |
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What does the spleen do to the blood |
It clears the blood of aged blood cells and foreign particles and is the site of immune reaction to blood-borne antigens |
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What is the spleen not essential for |
life in adult individuals |
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What role does trabeculae play in the spleen |
Connective tissue capsule surrounds the spleen, giving trabeculae that divide interior into compartments. |
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What is in the trabeculae |
arteries and veins |
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What does the spleen exhibit |
Not distinct cortex and medulla but it has white and red pulp |
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White pulp |
dark staining lymphoid aggregation or lymphatic nodules surroundinga central artery, branch of trabecular arteries, located atthe peripheryg |
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What does the lymphatic nodules containe |
germinal centers |
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Red pulp |
-pulp (rich in blood vessels) consists of spleniccords and splenic sinusoidsor venoussinuses |
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What does red pupl contain |
pulparteries, venous sinuses and splenic cordsj*4e |
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splenic cord |
-network of reticular fibers containing macrophages, lymphocytes, plasma cells, located betweenvenous sinuses` |
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Splenic sinusoids |
-interconnected blood channels draining splenic blood into larger sinuses that will leavespleen via splenic veinfx |
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What is the function of the spleen |
-Filters blood and site of immune response to bloodborne pathogensg |
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Red pulp |
-dense network of reticular fibers containingerythrocytes, macrophages, lymphocytes, plasma cells |
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Main function of red pulp |
-filter the blood; removes microorganisms, antigens and aged or abnormal erythrocytesfrom the blood fD |
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What does macrophages do in the spleen |
-Macrophages break down hemoglobin of aged erythrocytesFD03C20} |
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White pulp |
immunecomponent of the spleen- Lymphatic tissuej*4e |
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What lymphatic cells surround the arteries |
-Lymphatic cells surrounding central arteries are Tcells3C20} |
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What are the lymphatic nodules containing |
Mainly B cells |
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What is located in the white pulp |
Antigen-presenting cells and macrophages |
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What is th purpose of white pulp |
-Detect trapped bacteria and antigens and initiateimmune response against them |
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Importance of white pulp during fetal life |
-During fetal life, spleen is haematopoietic organ, producing erythrocytes and granulocytestml>fD |
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What does the spleen contain an important resevoir for |
Blood |
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What is the palatine tonsil |
-Aggregates of lymphatic nodules located in the oralcavityD03C20} |
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What is the relationship between tonsils and connective tissue |
-Not surrounded by aconnective tissue capsule |
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What covers the surface of the tonsil |
-Surface protected by stratified squamous nonkeratinized epithelium |
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What invaginates each tonsil |
-deep grooves called tonsillarcrypts (also lined by stratified squamous nonkeratinized epithelium |
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What is below the epithelium |
1) numerouslymphatic nodules that Can merge with each other 2) Present lighter germinal center |
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What is underlying the palatine tonsil |
-connective tissue capsule with trabeculae- |