Lymphoid Organs Flashcards by Keizel Galupo

Provides defense or immunity against infectious agents ranging from viruses to multicellular parasites

immune system

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Preesixting nonspecific defense that involves immediate and nonspecific actions

innate immunity

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Natural killer cells that destroy various unhealthy host cells including those infected with virus or bacteria as well as certain potentially tumorigenic cells

Phagocytes

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Specific type of immunity that is acquired gradually by exposure to microorganisms; slower to respond

adaptive immunity

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These are derived from monocytes that become activated against specific invaders by being presented with specific molecules from those cells by APCs

B & T lymphocytes

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aimed at specific microbial invaders and involve production of memory lymphocytes

adaptive immune responses

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A response that involves antibody production

humoral

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A response that involves cytotoxic elimination via CDB

Cellular

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A molecule recognized by cells of the adaptive immune system and typically elicits a response from these cells

antigen

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A glycoprotein of the immunoglobalin family that interacts with an antigenic determinant that is secreted by plasma cells in response to antigen

antibodies

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Assist immune responses by producing cytokines that promote differentiation of B cells into plasma cells

helper t cells

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activate macrophages to become phagocytic, activate cytotoxic lymphocytes, and induce many parts of an inlammatory reaction

helper t cells

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represents cellmediated immunity

cytotoxic t lymphocytes

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allowing immune tolerance, maintaining unresponsiveness to self-antigens and suppressing excessive immune responses

regulatory cells

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acts to supplement the central tolerance that develops in the thymus

peripheral tolerance

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Group of cells, tissues, and organs that monitor body surfaces and internal fluid compartments and react to the presence of potentially harmful substances

lymphoid organs

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primary or central lymphoid organ in which T cells are produced

thymus

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Its main function is the induction of central tolerance, which along with regulatory T cells prevents autoimmunity

thymus

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A potent source of cytokine which is necessary for the maturation and differentiation of T lymphocyte

Thymic or Hassall’s corpuscles

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Provide a framework for the developing t cells

epithelioreticular cells

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Epithelioretricular Cell:

functions as a barrier that isolates developing T cells from the connective tissue of the organ

type 1

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Epithelioretricular Cell:

express MHC and MHC II molecules, which are involved in thymic cell education

Type II

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Epithelioretricular Cell:

Functional barrier, possess MHC I and MHC II molecules

Type III

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Epithelioretricular Cell:

They create the barrier at the corticomedullary junction

Type IV

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Epithelioretricular Cell: Provide the cellular framework of the medulla and to compartmentalize groups of lymphocytes

Type V

Epithelioretricular Cell: form the most characteristic feature of the thymic medulla, the thymic (Hassall's) corpuscles

Type VI

Protects developing lymphocytes in the thymus from exposure to antigens

Blood thymus barrier

Thymus has an ________ lymph vessel but no __________ lymph vessel so as to protect the developing lymphocytes from exposure to external antigens.

efferent and afferent respectively

Occurs in the cortex and allows survival only of T cells with functional TCRs recognizing MHC Class I and class II molecules

Positive selection

occurs in the medulla and allows survival only of T cells that do not tightly bind self-antigens presented on dendritic cells there

Negative selection

The ff. are secondary lymhoid structures where most lymphocytes are activated by antigen presentation, except A. MALT B. Lymph nodes C. Spleen D. AOTA E. NOTA

E. NOTA

Discrete concentrations of lymphocytes contained in a meshwork of retricular cells

Lymphatic nodules

A lymphatic nodule consisting chiefly of small lymphocytes

Primary nodule

Contains large immature lymphocytes (lymphoblasts and plasmablasts)

Germinal center

A morphologic indication of lymphatic tissue response to antigen

Germinal center

Develops when a lymphocyte that has recognized an antigen returns to a primary nodule and undergoes proliferation

Germinal center

Its presence represent a cascade of events that includes activation and proliferation of lymphocytes, differentiation of plasma cells and antibody production

Germinal center

Large, irregular masses of lymphoid tissue in the mucosa of the posterior oral cavity and nasopharynx where their cells encounter antigens entering the mouth and nose

Tonsils

Deep invaginations in which the epithelial lining is densely infiltrated with lymphocytes and other leukocytes

Tonsillar crypts

Inflammation of the tonsils

tonsillitis

Identify the type of tonsil being referred to: Stratified squamous epithelium; continuous w/ esophagus

Palatine tonsils

Identify the type of tonsil being referred to: Covered by stratified squamous epithelium; lack distinct capsules; near the oral cavity

Lingual tonsils

Identify the type of tonsil being referred to: Pseudostratified ciliated columnar epithelium, and has a thin underlying capsule, lacks crypts; near w/ oropharynx and continuous with the respiratory tract

Pharyngeal tonsils

Consist of numerous aggregations of lymphatic nodules containing T and B lymphocytes

Peyer Patches

A short, small diameter projection from the cecum with which the lamina propia is heavily infiltrated w/ lymphocytes and contains numerous lymphatic nodules

Vermiform appendix

bean-shaped, encapsulated structures distributed throughout the body along the lymphatic vessels

Lymph node

T or F. Lymph nodes are present along the major vessels of the neck and in the thorax and abdomen but not in the axillae (armpits) or groin.

False. Lymph nodes are present in the axillae (armpits) and groin, along the major vessels of the neck, and in the thorax and abdomen, and especially in the visceral mesenteries

Constitutes a series of in-line filters of lymph that defend against the spread of microorganisms and tumor cells

Lymph node

provide enclosed environments for antigen presentation and development of plasma cells secreting non-IgA antibodies

Lymph node

Most abundant cells of lymph nodes

Lymphocytes Plasma Cells Dendritic Cells Macrophages APCs

Convey lymph toward the node and enter it various points on the convex surface of the capsule

Afferent lymphatic vessels

Convey lymph away from the node and leave the hilum

Efferent lymphatic vessels

Also composed of dense connective tissue, which extend from the capsule into the substance of the node, forming a gross framework and cuts cortex into various lobules

Trabeculae

allows easier filtration of the lymph

Reticular tissue

Forms the outer portion of the node except at the hilum

Cortex

Receives lymph from the afferent lymphatics

Suncapsular sinus

Spherical or oval aggregates of lymphocytes that are formed largely by helper T lymphocyte and proliferating B lymphoblasts

Lymphoid nodules

Identify the correct pair: A. Primary Nodule: with germinal center; Secondary nodule: without germinal center B. Primary Nodule: Without germinal center; Secondary nodule: with germinal center

B. Primary Nodule: Without germinal center; Secondary nodule: with germinal center

These are covered with antibody antigen complexes bound to receptors for complement proteins and for immunoglobulin FC regions, causing B cells to attach, become activated and aggregate as a small primary lymphoid nodule

FDC (Follicular Dentritic Cell)

With its help, B cells would now form a much larger and more prominent secondary lymphoid nodule

adjacent T helper cells

Its rapid profileration in the germinal center causes smaller naive lymphocytes to be pushed aside and crowded together peripherally as then the follicular mantle

activated B lymphoblast

Contains lymphoid tissue rich in T cells

Paracortex

Specialized postcapillary venules represent an important entry point for most (90%) circulating lymphocytes into lymph node

High endothelial venules (HEVs)

Dilated spaces lined by discontinuous endothelium that separate the medullary cords

Medullary sinuses

The spleen is about the size of a __________________.

Clenched fist

Contains the largest single accumulation of lymphoid tissue in the body

spleen

only lymphoid organ involved in filtration of blood, making it an important organ in defense against blood-borne antigens

spleen

main site of old erythrocyte destruction and the production site of antibodies and activated lymphocytes, which here are delivered directly into the blood

spleen

Splenic pulp: Restricted to the smaller areas usually surrounding central arterioles

White pulp

Splenic pulp: Occupies most of the parenchyma

Red pulp

Consists of a thick accumulation of lymphocytes surrounding an artery

White pulp

Branch of the splenic artery

central artery

Compose of lymphocytes that aggregate around the central

Periarterial lymphatic sheath (PALS)

Contains large number of red blood cells that it filters and degrades

Red Pulp