HISTO: Lymphatic System Flashcards
(145 cards)
1
Q
Specific lymphoid organs
A
Thymus, spleen, lymph nodes
2
Q
MALT =
A
Mucosa-associated lymph tissue, in respiratory, reproductive and urinary system
3
Q
GALT =
A
Gut-associated lymphatic tissue, e.g. Tonsils, Peyer’s patches and appendix. Aggregates of lymphocytes. e.g. Lamina propria (plasma cells)
4
Q
All Lymphocytes originate in
A
Bone marrow
5
Q
T lymphocytes mature in the
A
Thymus
6
Q
Any substance that can induce a specific immune response is called an:
A
antigen
7
Q
Immune cells react to small molecular domains of the antigen called:
A
Epitopes
8
Q
An immune response is generated against a specific antigen, which can be:
A
- soluble substance (e.g., a foreign protein, polysaccharide, or toxin)
- an infectious organism, bacteria , protozoa, foreign tissue or transformed tissue
9
Q
First line of defense against microbial aggression is by:
A
Innate immunity (non-specific)
10
Q
The initial contact with antigen or foreign agent initiates a reactions that involve effector cells, and immunity conferred by “memory cells:
A
Adaptive immunity (specific)
11
Q
Various secreted substances that neutralize foreign cells:
A
thiocyanate in saliva
lysozyme
interferon
complement in serum
12
Q
Adaptive immunity induces _____ against antigens through somatic rearrangements of genes that encode immunoglobulins and specific receptors on T lymphocytes
A
acquired resistance
13
Q
Production of proteins called antibodies that mark invaders for destruction by other immune cells is which type of defense?
A
Humoral immune response
14
Q
Destruction of transformed and virus-infected cells, etc. by specific “killer” cells is which type of defense?
A
Cellular immune response
15
Q
Lymphocytes T (approximately 60- 80%) in blood or lymph represent a circulating pool of:
A
immunocompetent cells
16
Q
These cells exit the systemic circulation to enter the lymphatic tissue (surveillance).
A
T lymphocytes
17
Q
This population (approximately 30%) migrate directly to the tissues and lymphoid organs:
A
B lymphocytes
18
Q
Where a B lymphs found?
A
in the connective tissue that underlies the lining epithelium of the respiratory, gastrointestinal, and urogenital tracts
19
Q
Are part of nonspecific (innate) immunity, are named for their ability to kill certain types of target cells. They constitute about 5% to 10% of circulating lymphocytes
A
NK cells (natural killer)
20
Q
Participate as antigen presenting cells (APCs), that phagocytose and process antigens, attach them to MHC II and present them to T-cells
A
Supporting cells
21
Q
Examples of Supporting cells:
A
Reticular cells
dendritic cells
macrophages
Langerhans cells
epithelioreticular cells
22
Q
What are cluster of differentiation (CD) markers?
A
Membrane markers for cells in lymphatic tissue to identify
23
Q
B-lymphocytes markers:
A
CD9, CD19, CD20
24
Q
T-lymphocytes markers:
A
CD2, CD3, CD5, CD7, helper CD4+ and cytotoxic CD8+, CD40L
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NK cells markers:
CD16, CD56 and CD94
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products of a “supergene” located on chromosome 6 in humans
MHC I and MHC II
from major histocompatibility gene complex
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Where are MHC I expressed?
Is expressed on the surface of all nucleated cells and platelets
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Presents peptides fragments (8 to 10 amino acids in length) to cytotoxic CD8+ T lymphocytes.
MHC I
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Where are MHC II expressed?
on a restricted population of cells known as antigen-presenting cells (APCs)
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present exogenous (foreign) peptides (18 to 20 amino acids) to helper CD4+ T lymphocytes
MHC II
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These cells are further subdivided by their ability to secrete cytokines
Helper CD4+ T lymphocytes
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Which lymphocytes are MHC II restricted
CD4+ T
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T lymph important surface markers
CD4 and CD8
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synthesize interleukin 2 (IL-2), interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α)
Helper TH1 cells
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TH1 helper cells intercact with?
cytotoxic CD8+ T lymphocytes (CTLs), NK cells, and macrophages
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interact with B lymphocytes and are essential for initiating antibody-mediated immune responses that control extracellular pathogens
Helper TH2 cells
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What does TH2 synthesize?
IL-4, IL-5, IL-10, and IL-13
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Their principal function is to destroy extracellular bacteria and fungi by recruiting neutrophils to the site of inflammation
Helper TH17 cells synthesize IL-17 and IL-22
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What are defensins?
antimicrobial peptides
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Kill other target cells such as virus-infected cells, cancer-transformed cells, cells infected with parasites, and transplanted cells.
Cytotoxic CD8+ T lymphocytes (CTLs)
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Cytotoxic CD8+ T lymphocytes (CTLs) produce:
proteins called fragmentings and perforins that create holes in the cell membrane and induce apoptosis
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Which lymphocytes are MHC I restricted
Cytotoxic CD8+ T lymphocytes (CTLs)
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T lymphocytes that can functionally suppress an immune response to foreign and self- antigen by influencing the activity of other cells in the immune system
Regulatory (suppressor) T lymphocytes
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regulatory cells that can diminish the ability of T lymphocytes to initiate immune responses:
CD4+CD25+FOXP3
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Which gene can cause polyendocrinopathy, enteropathy, X- linked (IPEX) syndrome, recessive disorder characterized by dysfunction of the T regulatory (Treg)
Mutations of the FOXP3 gene
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Represent a small population of T cells (<5%) with a distinct T cell receptors (TCRs) on their surface made of one γ chain and one δ chain
Gamma/delta (γ/δ) T lymphocytes
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Where do Gamma/delta (γ/δ) T lymphocytes develop?
These cells develop in the thymus and migrate into various epithelial tissues (e.g., the skin, oral mucosa, intestines, and vagina).
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Which lymphs participate in humoral immunity?
B lymphs
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B cells express which molecules on the cell surface?
major histocompatibility complex II (MHC II)
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During differentiation, the BCR isotope switches from ___ to ___
immunoglobulin M (IgM) in immature B cells to a mixture of immunoglobulin D (IgD) and IgM in mature
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what are Immunoglobulins?
Antibodies that are circulating plasma glycoproteins that interact with specific antigen
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Late stage in differentiation of B-lymphocytes
plasma cells
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where are plasma effector cells found?
Abundant in medullary cords of lymph nodes, marginal zone and cords of spleen and connective tissue
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A few antigen-specific B lymphocytes remain in circulation as:
memory cells
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IgG function:75-80%
Longest half- life (23 days) of all five. Stimulates chemotaxis. Activates complement. Crosses the placenta
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IgM function:5-10%
Produced in initial immune response. Activates complement system and macrophages
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IgA function:10-15%
Glandular secretions: saliva, tears, milk, mucus. Aids in defense against microbes and foreign molecules penetrating body via cell linings of these cavities
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IgD function:
In the membrane of lymphocytes. Acts as an antigen receptor on surface of mature B lymphocytes
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IgE function:
Fc portion binds to mast cells and basophils. Responsible for anaphylactic and hypersensitive reactions. Increased levels in parasitic infections
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the initial response to an antigen
inflammation
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Degradation of antigens by macrophages may lead to
presentation of a portion of the antigen to immunocompetent cells.
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Primary immune response is:
characterized by a lag period of several days before antibodies (mostly IgM) or specific lymphocytes directed against the invading antigen can be detected in the blood1
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Secondary immune response is:
Usually more rapid and intense (characterized by higher levels of secreted antibodies, usually of the IgG class). The secondary response is the basis of most immunizations for common bacterial and viral diseases.
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Interactions between an antigen–MHC complex with its specific T-cell receptor (TCR) requires
costimulary signal from CD28 and B7
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in cell-mediated immune response, cytotoxic CD8+ T lymphocytes (CTLs) target destroy
virus infected cells
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these cells Participate in antibody-dependent cell-mediated cytotoxicity (ADCC)
Nk cells
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Cytokines are
soluble polypeptide substances, synthesized mainly by activated T lymphocytes
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Interleukins are synthesized mainly by
helper CD4+ T lymphocytes
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the first cytokine to be discovered and characterized
Interleukin 2 (IL-2) induces proliferation of T cells
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which kill HIV-infected helper CD4+ T cells
Cytotoxic CD8+ T cells
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play a critical role in the acute rejection of transplanted cells and organs
Cytotoxic T cells
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X-linked agammaglobulinemia causes:
B lymphocytes do no develop, resulting in scarcity of plasma cells and immunoglobulins
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mediated by IgE antibodies that are responsible for the antibody-induced discharge of mast cell or basophil granules
hypersensitivity reaction
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involved in the pathogenesis of many autoimmune and infectious diseases and also play an important role in the prevention of graft rejection
Regulatory (suppressor) T cells
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Blocking the B7-CD28 costimulatory signal can treat:
rheumatoid and juvenile idiopathic arthritis and is in clinical trials for prevention of transplant rejection
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What can guard the body against pathogenic substances and are the site of the initial immune response?
Diffuse lymphatic tissue and lymphatic nodules
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Primary nodule:
* Rounded aggregation of closely packed small lymphocytes.
* Mesh of follicular dendritic cells (stellate cells) as a framework
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Secondary nodule with germinal center:
* A germinal center is located in the central region of the nodule and appears lightly stained in histologic sections. The germinal center develops when a B lymphocyte that has recognized an antigen undergoes extensive division and proliferation.
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lymphoblasts:
The lighter staining is attributable to presence of the large lymphocytes
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plasmablasts:
migratory B cells committed to secreting antibodies
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Solitary lymphoid nodule is:
* Lamina propria of gut and respiratory tract
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What are Peyer’s patches?
Are located in the ileum (distal portion of the small intestine) and consist of numerous aggregations of lymphatic nodules containing T and B lymphocytes.
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an important component of the immune functions of small intestine:
IgA
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where does the Appendix arise from?
from the cecum (no villi). The lamina propria is heavily infiltrated with lymphocytes and contains numerous lymphatic nodules. Chronic inflammatory changes
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form a ring of lymphatic tissue at the entrance of the oropharynx:
tonsils
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palatine tonsils:
Stratified squamous epithelium non-keratinized. Many tonsillar
crypts. Incomplete fibrous capsule
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lingual tonsils:
Stratified squamous epithelium non-keratinized. 1 crypt.
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Pharyngeal tonsils:
Pseudostratified columnar epithelium, ciliated with goblet cells. Plicae (folds). Thin capsule.
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the principal molecule of mucosal immunity:
IgA
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filter lymph along the pathway of lymphatic vessels and initiate adaptive immune responses to antigens
lymph nodes
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They express surface molecules and produce substances (chemokines) that attract lymphocytes and dendritic cells.
reticular cells (type III collagen)
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are bone-marrow derived antigen presenting cells (APCs) Very efficient at antigen presentation. They express exceptionally high level of MHC II and costimulatory molecules necessary for activation of T cells
dendritic cells
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In the lymph node, DCs are usually localized in _____ rich areas
T lymphocyte–
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Usually found in germinal centers. They are NOT Antigen Presenting cells APCs. They lack MHC II molecules.
follicular DCs
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Phagocytic and APC, express MHCI, MHCII and costimulatory signals
macrophages
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Superficial (outer) cortex (SC) of lymph node has:
Lymphoid nodules, germinal centers (B-lymphocyte differentiation), diffuse lymphoid tissue
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Deep cortex (DC) (paracortex) of lymph node has:
Diffuse lymphoid tissue
Mainly T-lymphocytes.
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is the thymus dependent region of the lymph node
Deep cortex (DC) (paracortex)
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T cells are distributed within the ____ cortex
Deep cortex
100
Location of B cells in lymph node
the accumulations of which are found within germinal centers (GC) of the superficial cortex (SC).
101
Beneath the capsule of the lymph node is the
subcapsular sinus (afferent)
102
Lymphatic sinuses are lined by
macrophage processes
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what are Medullary cords?
Aggregations of lymphoid tissue around lymph sinuses. Small lymphocytes.
104
Both B and T cells leave the bloodstream through:
High endothelial venules (HEVs).
105
HEV endothelium expresses:
water channels (aquaporin-1
[AQP1] molecules
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what is Lymphadenitis?
a reactive (inflammatory) lymph node enlargement, is a common complication of microbial infections. “swollen glands”
107
which pathway regulated lymphocytes exit
S1P exit pathway
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DiGeorge Syndrome (DGS) is a
primary immunodeficiency, often characterized by cellular T-cell deficiency (lack of T lymphocytes in the paracortex of the lymph node)
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Sentinel lymph node is:
the first one downstream from the region of the tumor
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lymphadenopathy is:
The normal histological organization is lost; the node enlarges, becomes filled with lymphocytes
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Lymphoepithelial organ situated in the superior mediastinum anterior to the great vessels
thymus
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thymus develops from:
Common lymphoid progenitor (CLP) cells, from the bone marrow, to become immunocompetent T lymphocytes invade the region
----bilaterally from the third and the fourth branchial (oropharyngeal) pouch
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thymus capsule is formed by:
dense irregular ct
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thymus cortex has:
Closely packed developing T lymphocytes with their intensely staining nuclei (also called thymocytes)
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thymus medulla has:
Loosely packed T lymphocytes and a large number of epithelioreticular cells. Contains mostly large lymphocytes.
116
involution of thymus can be:
Age involution
Accidental involution due to stress, radiation, steroids that decrease T lymphocytes production.
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Type I epithelioreticular cells of thymus cortex
The occluding junctions between these cells reflect their function as a barrier that isolates developing T cells from the connective tissue of the organ
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Type II epithelioreticular cells: thymus CORTEX
Form maculae adherents (desmosomes) that join long cytoplasmic processes of adjacent cells, these cells are stellate shape. They have a large nucleus with abundant euchromatin.
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involved in thymic cell education in type II
MHC I and MHC II
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Type III epithelioreticular cells: thymus CORTEX
They form occluding junctions between cytoplasmic processes of adjacent cells.
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responsible for phagocytosis of T cells that do not fulfill thymic education requirements, these T cells die before leaving the cortex
macrophages
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Thymus-blood barrier three major elements:
1) Capillary endothelium with occluding junctions and its basal lamina
2) Perivascular connective tissue space occupied by macrophages
3) Type I epithelioreticular cells with occluding junctions and their basal lamina
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Type IV epithelioreticular cells thymus MEDULLA
ocated between the cortex and the medulla close to type III cells. They possess occluding junctions between adjacent cells and also type III cells. In cooperation with type III cells, they create the barrier at the corticomedullary junction.
124
Type V epithelioreticular cells: thymus medulla
. Like the type II cells located in the cortex, are joined by desmosomes to provide the cellular framework of the medulla and to compartmentalize groups of lymphocytes.
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Type VI epithelioreticular cells form the thymic (Hassall) corpuscles:
Studies of these cells reveal keratohyalin granules, bundles of cytoplasmic intermediate filaments. Are joined by desmosomes. The center of a thymic corpuscle may display evidence of keratinization.
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in thymus: The immunocompetent T lymphocytes migrate to ___ in spleen
Periarterial lymphatic sheath (PALS)
127
hormones that are necessary for the maturation of T cells in thymus:
Thymulin, Thymic humoral factor, Thymosin-I, Thymopoietin. Colony stimulating factors and Interferon γ.
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a phenomenon called cross-talk:
T cells control the microarchitecture of the thymic epithelioreticular cells
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Largest lymphoid organ, situated left upper quadrant of the abdominal cavity and has a rich blood supply.
spleen
130
spleen function:
Filters blood to clear it of particulate matter and senescent
erythrocytes.
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spleen white pulp:
thick accumulation of lymphocytes surrounding an artery.
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spleen red pulp:
Irregularly shaped blood vessels, and large numbers of red blood cells that it filters and degrades.
* venous sinuses
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Macrophages and______, increase in number towards the periphery of the PALS and during immune-responses to blood-borne antigens.
specialized dendritic cells
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Periarterial lymphatic sheath (PALS) is:
Made up of T-lymphocytes of the recirculating pool in loose framework of reticular cells and fibers.
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Splenic cords (cords of Billroth) are:
meshwork of reticular cells and reticular fibers. Large numbers of erythrocytes, platelets, macrophages, monocytes, lymphocytes, dendritic cells, plasma cells, and granulocytes reside in splenic cords
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Splenic sinuses are
special sinusoidal vessels lined by rod-shaped endothelial cells
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In splenic sinus Basal lamina is
present but incomplete.
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Central artery branches→
penicillar arterioles→enter red pulp and continue as arterial capillaries.
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The splenic artery branches many times in trabeculae to form
trabecular arteries.
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sheathed capillaries are:
arterial capillaries are surrounded by aggregations of macrophages
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macrophage in red pulp function:
function is to remove particulate matter and senescent cells from blood.
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In the open circulation, which occurs in humans, penicillar arterioles empty directly into
reticular meshwork of the cords rather than connect to the endothelium-lined splenic sinuses
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the only route by which blood returns to the venous circulation.
open circulation
144
Hemopoietic function of spleen:
* Removal and destruction of senescent, damaged, and abnormal erythrocytes and platelets.
* Retrieval of iron from erythrocyte hemoglobin.
* Formation of erythrocytes during early fetal life.
* Storage of blood, especially red blood cells, in some species.
* These functions are accomplished by the macrophages embedded in the reticular meshwork of the red pulp
145
Immune system functions of spleen include:
Antigen presentation by APCs and initiation of immune response
* Activation and proliferation of B and T lymphocytes
* Production of antibodies against antigens present in blood
* Removal of macromolecular antigens from blood.
* Proliferation of B- lymphocytes and plasma cells (White pulp). Production and secretion of antibodies
