Lymphatic System Flashcards Preview

Histology / Embryology Unit 3 > Lymphatic System > Flashcards

Flashcards in Lymphatic System Deck (67)
Loading flashcards...

What are the primary or central lymphatic organs?

Bone marrow + thymus


What are the secondary lymphatic organs?

Lymphatic nodules, tonsils, appendix, lymph nodes, and spleen


What are the cells of lymphatic tissue?

B lymphocytes, T lymphocytes, plasma cells, macrophages, and antigen presenting cells


What defines an antigen?

Any substance that can induce an immune response. They can be soluble substances, infectious microorganisms, foreign tissue, transformed or cancerous cells


What happens to antigen-antibody complexes?

They are formed by Ig's secreted by plasma cells + the respective antigen and are eliminated by the body


What is the innate / nonspecific immune response?

First line of defense: skin, internal epithelial linings, chemical (low pH), secretions like lysozymes and proteins in saliva. If antigens get past these barriers, it is destroyed by other elements of the immune system.


What is humoral vs cellular immunity? What are they a part of?

Both a part of the acquired / adaptive immune response.
Humoral: Secretion of antibodies by plasma cells which differentiate from B cells
Cellular: Activation of T lymphocytes to destroy virus infected cells


What are CD proteins and why are they useful?

They are transmembrane proteins expressed on T cells, called "Cluster of Differentiation". They can be used to distinguish between T lymphocytes.
CD4 = Helper, CD8 = Cytotoxic


What are MHC molecules? Why do they generally exist for the immune system?

Group of transmembrane proteins which help the immune system recognize self vs non-self


Where is MHC I expressed? What is their function?

On all nucleated cells and on platelets. TH=hey act as a target to allow the elimination of abnormal host cells (viral or cancerous) whenever they present peptide fragments to cytotoxic CD8+ T-lymphocytes.


Where is MHC II expressed? What is their function?

Expressed on surface of antigen presenting cells (APCs) such as dendritic cells and macrophages. They present foreign peptides to CD4+ T-helper cells to activate them.


What is a T-cell receptor (TCR) and how does it work?

They are expressed by T-lymphocytes and recognize a single antigen by interacting with MHC (1 or 2, depending on cell)


What is a B-cell receptor (BCR) and how does it work?

BCRs are antibodies and also recognize a single antigen. After recognizing an antigen, it leads to differentiation of a B lymphocyte to a plasma cell


What does it mean for a lymphocyte to be immunocompetent?

Circulating T and B cells are immunocompetent because they are capable of developing an immune response following exposure to antigen


Where do T-cells differentiate? What happens to them? What is their prevalence?

They differentiate in the thymus by antigen-INDEPENDENT differentiation, where they will become immunocompetent cells. They have a long lifespan and enter the bloodstream / lymphatic system to make up 60-80% of lymphocytes. They can be found in lymphatic tissue or secondary lymphatic organs


What are the functions of CD4+ T Helper cells?

They promote activation and proliferation of B cells, and CD8+ T cells that have encountered their specific antigens


What is the function of CD8+ T cells?

They are cytotoxic, and kill cells infected with intracellular pathogens, or destroy transformed cells or cancerous (tumor) cells


Where do B-cells differentiate? What happens to them? What is their prevalence?

They differentiate in the bone marrow by antigen-INDEPENDENT differentiation, making up 20-40% of lymphocytes. They will move from blood or lymph to become part of lymphatic tissue / secondary lymphatic organs.


What is the mononuclear phagocytic system? What cells are included?

System of cells which recognize foreign molecules, endocytose and process them, then display them on MHCII to T-helper cells.
1. Macrophages - CT and lymphatic organs
2. Kupffer cells - liver
3. Langerhan's cells - epidermis
4. Dendritic cells - spleen + lymph nodes


What are some of the odd functions of macrophages in immune response?

Secretion of cytokines, phagocytosis of bacteria and foreign antigens, can also form a "multinucleate foreign body giant cell" - isolation of certain pathogens via granuloma.


How are lymph vessels formed?

They are formed by networks of blind-ended capillaries in loose connective tissue, especially skin and mucous membranes


What do lymphatic vessels carry? What does it contain?

Lymph, tissue fluid which is a filtrate of blood plasma. Contains:
1. Proteins and lymphocytes to return to blood
2. Antigens bound to lymph nodes
3. Lipids and lipid-soluble vitamins absorbed in GI tract


How can lymph vessels be recognized? How does lymph flow?

They have very thin walls with no RBCs, made of endothelium. It flows by bulk flow (skeletal muscle action and respiratory movement) since there is no pump.


Where does lymph ultimately drain?

After moving into lymph nodes via afferent lymphatic vessels and leaving via efferent lymphatic vessels, it drains into the right or left lymphatic duct which combines with the venous system at the base of the neck. Ultimately it becomes a part of vascular circulation


Where is diffuse lymphatic tissue found? What is it called in the gut?

In the loose connective tissue lamina propria of the GI tract, respiratory tract, and genitourinary tract. It is not enclosed in connective tissue capsule.

GALT = gut-associated lymphatic tissue


What is the function of diffuse lymphatic tissue?

Recognize antigens that have broken through nonspecific barriers.


What are lymph nodules?

Localized concentrations of lymphocytes that can be found in grounds in GI, respiratory, and genitourinary tracts. They are not encapsulated in connective tissue


What is a primary vs secondary lymphatic nodule?

Primary - uniformly distributed and densely basophilic, full of small, inactive B cells.
Secondary - Pale, inner "germinal center" made of large activated B cells. Dark, outer mantle zone / corona which is small B lymphocytes encircling the germinal center.


Where are the permanent locations of secondary lymph nodules?

Outer cortex of lymph nodes, appendix, ileum of small intestin, Peyer's patches, spleen white pulp, and tonsils.

Though they can form anywhere in the body


What are tonsils?

Aggregates of primary and secondary lymphatic nodules with an epithelial surface covering and a connective tissue base