Lecture 4: Lymphoid Tissue Flashcards
What are the primary lymphoid organs and what is their function?
Thymus
Red bone marrow
Produce lymphocytes needed to recognize antigens
_________ lymphoid organs consist of diffuse lymphoid tissue where lymphocytes are activated in response to Ags
Secondary
Lymphoid tissue can be classified functionally as primary vs. secondary. It can also be classified as _____________ vs. ____________
Non-encapsulated
Capsulated
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
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
Nodular lymphoid tissue consists only of _______ lymphocytes that are inactive or naive. The cells are _________ distributed and lack a _______ _________
Small; uniformly; germinal center
What happens when a primary follicle is exposed to Ag?
Becomes a secondary follicle which will differ in appearance
What type of epithelium is displayed by primary nodules?
Nonkeratinized stratified squamous
Where are primary nodules/follicles found?
Esophagus
Oral cavity
Anus
Vagina
[areas exposed to outside environment]
Visually, how would you see a difference between primary and secondary follicles?
Secondary will have a germinal center, while primary do NOT
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
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
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
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
Do palatine tonsils contain germinal centers?
Yes
Which tonsil exists as a single structure?
Pharyngeal tonsil
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]
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
The lingual tonsil is positioned along the base of the tongue and is covered with _______ _______ epithelium.
Stratified squamous
Does the lingual tonsil have germinal centers, crypts, or a capsule?
Germinal centers = yes
Varying number of crypts
Lacks a capsule
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
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
What type of non-encapsulated lymphoid tissue is the vermiform appendix?
Aggregate nodular
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
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?
No
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
