Lecture 4: Lymphoid Tissue Flashcards by Sarah Gillen

What are the primary lymphoid organs and what is their function?

Thymus
Red bone marrow

Produce lymphocytes needed to recognize antigens

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_________ lymphoid organs consist of diffuse lymphoid tissue where lymphocytes are activated in response to Ags

Secondary

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Lymphoid tissue can be classified functionally as primary vs. secondary. It can also be classified as _____________ vs. ____________

Non-encapsulated

Capsulated

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Non-encapsulated lymphoid tissue is diffuse and nodular. It can exist as single entities or aggregates. What are some examples?

Single: primary nodules and secondary nodules

Aggregate: tonsils, Peyer’s patches, Vermiform appendix

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Diffuse lymphoid tissue consists of __________ CT housing lymphocytes deep to epithelium

It is located in what 3 locations?

Reticular

GI tract, GU tract, respiratory passages

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Nodular lymphoid tissue consists only of _______ lymphocytes that are inactive or naive. The cells are _________ distributed and lack a _______ _________

Small; uniformly; germinal center

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What happens when a primary follicle is exposed to Ag?

Becomes a secondary follicle which will differ in appearance

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What type of epithelium is displayed by primary nodules?

Nonkeratinized stratified squamous

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Where are primary nodules/follicles found?

Esophagus
Oral cavity
Anus
Vagina

[areas exposed to outside environment]

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Visually, how would you see a difference between primary and secondary follicles?

Secondary will have a germinal center, while primary do NOT

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Secondary follicles have a germinal center which stains _______ than the outer portion. It posseses an outer ring called a _______, which contains smaller lymphocytes.

Memory cells will collect in the _________

Lighter; mantle

Mantle

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T and B lymphocytes have a distinct distribution regarding the secondary follicle/nodule. Where would you find each type of cell?

B cells localize to the follicle, in the germinal center and the mantle

T cells localize to the tissue surrounding the follicle

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Tonsils are large, irregular masses of lymphoid tissue that help protect against inhaled or ingested substances. They can be partially encapsulated.

What are the 3 tonsils?

Pharyngeal
Palatine
Lingual

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The palatine tonsil is characterized by ___________ ___________ epithelium and possesses 10-20 deep invaginations called ________ _________.

The epithelial lining is densely populated with __________. Dense CT acts as partial __________.

Stratified squamous; tonsillar crypts

Lymphocytes; capsule

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Do palatine tonsils contain germinal centers?

Yes

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Which tonsil exists as a single structure?

Pharyngeal tonsil

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The pharyngeal tonsil is located at the posterior wall of the _____________. It is covered with ___________ _________ ciliated epithelium.

It has a thin, underlying __________.

Nasopharynx; pseudostratified columnar

Capsule [still categorized as non-encapsulated]

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Does the pharyngeal tonsil have crypts or germinal centers?

No crypts, just invaginated mucosa with shallow infoldings

Only has GC’s after responding to an Ag

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The lingual tonsil is positioned along the base of the tongue and is covered with _______ _______ epithelium.

Stratified squamous

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Does the lingual tonsil have germinal centers, crypts, or a capsule?

Germinal centers = yes

Varying number of crypts

Lacks a capsule

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What type of non-encapsulated lymphoid tissue is MALT, and where is it found?

Aggregate nodular

Typically found in GI tract (GALT), respiratory airways (BALT), and urinary tract

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GALT is aggregate nodular tissue that is prominent in small intestines, especially the ________.

_________ ________ are large collections of lymphatic nodules.

It is characterized by an abundance of ______, and is covered by __________ ________ epithelium with ________ cells

Ileum

Peyer patches

Villi; simple columnar; goblet

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What type of non-encapsulated lymphoid tissue is the vermiform appendix?

Aggregate nodular

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The vermiform appendix is a short, small-diameter projection off the ______ that is almost completely filled with lymphoid tissue.

It is covered in ______ ______epithelium with _______ cells.

It is characterized by _____, but lacks _____ or a _______

Cecum

Simple columnar; goblet

Crypts; villi; capsule

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Capsulated lymphoid tissue includes what 2 subcategories of lymphoid tissue?

Lobules Lacking lobules

What is the primary example of lobulated capsulated lymphoid tissue?

Thymus

What are the 2 examples of capsulated lymphoid tissue lacking lobules?

Spleen | Lymph nodes

The thymus is a _________ structure located in the ________. ___________ invade this tissue and proliferate. Lymphocytes then mature into ____ cells. It is functional at birth and remains active in T-cell production until puberty, followed by a period of _____________ (decreased activity of the thymus and it is replaced by _______ tissue)

Bilobed; mediastinum Lymphoblasts; T Involution; adipose

The thymus is surrounded by a _______ ______ capsule. Septa extend from capsule to penetrate the parenchyma, forming _______. The lobules posses a darker staining __________ and a lighter staining ________.

Connective tissue Lobules Cortex; medulla

Does the thymus contain lymphoid nodules or germinal centers?

What is the specific site of T lymphocyte maturation in the thymus, and what all is contained there?

Thymic cortex Contains T-lymphoblasts (thymocytes), macrophages, Thymic Epithelial cells (TECs)

What are the 2 types of cortical thymic epithelial cells?

Subcapsular (squamous) Cortical (stellate)

Which subtype of cortical TECs forms the cortical compartment? A subset will form a sheet like structure separating the cortex/medulla.

Subcapsular (squamous)

The cortical (stellate) cortical TECs produce the ____________ (keratin and desmosomes), as well as secretes _________ for T cell development

Cytoreticulum Cytokines

Where is the functional blood-thymus barrier?

In the cortex only

What forms the blood-thymus barrier?

TECs, basal lamina, and endothelial cells Macrophages prevent circulating antigens from reacting with developing T cells

The blood-thymus barrier consists of thymic cortical epithelial cells joined by _______, dual basal laminae produced by TECs and endothelial cells, and capullary endothelial cells linked by _________ ________

Desmosomes | Tight junctions

What part of the thymus houses mature T cells migrating from the cortex?

The thymic medulla

T cells in the thymic medulla enter ____________ _________ to exit the thymus

Postcapillary venules

What are the 4 major components in the thymic medulla?

TECs (medullary epithelial cells) Macrophages Dendritic cells Hassal's corpuscles

What are Hassal's corpuscles?

Closely packed whorls of keratinized TECs in the thymic medulla Secretes cytokines that aid in maturation of T cells

Which part of the thymus would you find the following? Immature/maturing T cells, subcapsular TECs, cortical TECs, and macrophages

Cortex

Which part of the thymus would you find the following? Mature T cells, medullary TECs, Hassall's corpuscle, dendritic cells, macrophages

Medulla

Where would you find the spleen and what does it do?

Found in left upper quadrant Initiates immune response to blood antigens Reservoir for platelets Recycling of erythrocytes Hematopoiesis

The spleen is surrounded by a CT capsule. ________ separates it into incomplete compartments. The parynchema contains _______ fibers. The _______ pulp is rich in lymphoid tissue. The ______ pulp is rich in RBCs. It is served by a single splenic artery and vein.

Trabeculae Reticular; white; red

Which pulp of the spleen is associated with the venous supply and contains platelets, erythrocytes, macrophages, and plasma cells?

Red pulp

Which pulp of the spleen consists of T and B cells?

White

The white pulp of the spleen is characterized by lymphoid nodules and _________ arteriole. __________ _______ ________ are T cells surrounding the arteriole. __________ zone consists of small lymphocytes surrounding the GC. _________ zone consists of a blend of lymphocytes that span from white to red pulp.

Central Periarteriolar lymphoid sheaths (PALS) Corona/mantle (MnZ) Marginal zone (MgZ)

The red pulp is involved in blood filtration and erythrocyte turnover. It is composed of splenic _______ and _______. The ______ are reticular tissue rich in macrophages and lymphocytes. The red pulp contains __________ arteries and _________-sheathed capillaries

Sinusoids; cords Cords Penicillar; macrophage

The splenic sinusoids of the red pulp are lined with _______ cells, which are specialized endothelial cells that separate healthy vs. unhealthy RBCs

Stave ("barrel" cells)

The splenic artery branches from the _______ ______, and divides into _________ arteries that enter into the parynchema.

Celiac trunk; trabecular

Trace splenic blood flow from the splenic artery to the splenic cords

``` Splenic artery Trabecular arteries Central arteriole (PALS) White pulp Penicillar arteries Splenic sinuses Splenic cords ```

Throughout splenic blood flow, ___________ remove old/dead erythrocytes from circulation, while viable erythrocytes re-enter circulation through the _________

Macrophages; sinuses

_________ is the clear, yellowish fluid comprised of interstitial fluid, solutes, and foreign materials

Lymph

Lymphatic ___________ are closed-ended tubules that are found among capillary beds

Capillaries

The human body has 400-450 _______ _____, which are small encapsulated structures positioned along lymphatic vessels

Lymph nodes

Where are the highest concentrations of lymph nodes?

Axilla Thorax Inguinal Around neck vasculature

What are the functions of the LNs?

Filter lymph Remove debris Facilitate Ab production Produce lymphocytes

The outer cortex of the lymph node receives lymph from _________ lymphatic vessels Sinuses converge at the __________ lymphatic vessel (singular) in the central medulla. The ___________ is the region between the cortex and medulla. The _______ refers to the exit for efferent lymphatics and entry for neurovasculature

Afferent Efferent Paracortex Hilum

Trace lymph flow through the LN from afferent to efferent

``` Afferent Cortex Paracortex Medulla Efferent ```

The ___________ __________ of the LN includes the major spces for lymph flow. Lymphatic follicles and germinal centers are restricted to the ______ of the LN. Immune cells are suspended on _________ fibers

Subcapsular sinus Cortex Reticular

Germinal centers of LNs contain activated follicles that have been presented with an antigen. Active B cells are contained in the _______ zone.

Mantle

Describe the cortical distribution of T and B cells in the LN

B cells localized to lymphatic follicle T cells localized to paracortex

_________ _________ _________ refer to the cuboidal lining of endothelial cells that facilitates movement of lymphocytes into lymphoid tissue

High endothelial venules

Where are high endothelial venules (HEVs) located?

Paracortex

Lymphocytes move from the blood into the LNs via HEVs through a process called ___________, which is promoted by integrins and glycoproteins

Diapedesis

The medulla of the LN is _______ staining than the cortex due to lower population of lymphocytes. It is characterized by medullary _______, which are masses of lymphoid tissue extending from the paracortex, as well as T cells, B cells, and plasma cells. It also contains medullary _______, which are dilated spaces that separate the medullary cords, as well as clusters of macrophages and neutrophils

Lighter Cords Sinuses

Lecture 4: Lymphoid Tissue Flashcards

(67 cards)