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115 Cards in this Set
- Front
- Back
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General function of lymphatic system
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monitors and protects body from xenogenous invaders regardless of route of entry
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General structure of lymphatic tissues and organs
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reticular (spongy) - allows easy poassage
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Vessels in lymphatic system that regulate passage of lymphocytes
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HEVs
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Method by which lymphatics PREVENT EDEMA
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collecting plasma exudate and ultimately return it to general circulation
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Most common mode by which most comon type of CAs spread
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lymphogenous spread
(most common type CA = carcinomas from epithelial tissue) |
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Definition of ANTIGEN
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any substance that induces a specific immune response
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Location of lymphocyte origination
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BONE MARROW
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Lymphocytes are covered with ____
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microvilli
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3 main classes of lymphocytes
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T cells
B cells NK cells |
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What percentage of circulating lymphocytes are T cells?
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65-75%
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Helper T cells, aka:
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CD4+ T lymphocytes
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3 functions of cytokines secreted by Helper T cells
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aiding Macrophages
stimulating CTL activity stimulating B cell proliferation & differentiation |
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CTLs, aka:
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CD8+ T lymphoctyes
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Percentage of circulating lymphocytes that are B cells
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5-10%
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Event that induces B cell proliferation and differentiation
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Exposure of naive B cells to antigens
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nuclear and cytoplasmic histological characteristics of:
PLASMA CELLS |
round, eccentric nucleus with "clock-face chromatin"
basophilic cytoplasm b/c of RER |
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2 types of differentiated B cells
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plasma cells (produce Abs)
memory B cells (rapid response to 2nd exposure) |
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Percentage of circulating lymphocytes that are NK Cells
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10-15% NK Cells
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NK cells recognize...
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transformed cells
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histological characteristics of NK cells
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larger than T&B cells
magenta granules in cytoplasm (lysozymes) |
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Most APCs belong to what family of cells?
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Mononuclear phagocytotic system (MPS)
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MPS cells are derived from what cell type?
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monocytes
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MPS cells that are not APCs
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osteoclasts
microglia |
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MPS cells that are APCs
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macrophages
Kupffer cells (perisinusoidal Mphages of liver) Langerhans' cells of epidermis denderitic follicular cells of spleen and nodes |
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APCs that do not belong to MPS
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B lymphocytes
epithelioreticular cells of thymus |
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Ability of T and B cells to bind to specific antigens = ____ or _____
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specificity or immunocompetency
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What occurs in primary lymphoid tissues?
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immature lymphocytes become immunocompetent
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primary lymphoid tissue for T cells
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thymus
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primary lymphoid tissue for B cells
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bone marrow
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What occurs within secondary lymphoid organs and tissues
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interaction btw Ag's, APCs, T cells and B cells is optimized
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3 types of secondary lymphoid tissues/organs
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lymph nodes
spleen MALT |
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4 things to know about THYMUS
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encapsulated
bi-lobed located primarily in superior mediastinum decreases dramatically in size after puberty |
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Thymic education involves expression and deletion of unique cell surface antigens called...
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Thymic education involves expression and deletion of unique cell surface antigens called CLUSTERS OF DIFFERNETIATION (CD) MOLECULES
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What proportion of T cells become properly educated in the thymus?
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1 in 10
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2 functions of:
Epithelioreticular cells of the thymus |
Epithelioreticular cells of the thymus
are APCs produce thymosin and thymopoietin hormones (paracrine action) |
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The outer capsule and trabeculae of the thymus are made of...
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dense CT
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trabeculae of the thymus contain...
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blood vessels
efferent lymphatics nerves |
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thymus capsule and CT stroma are derived from which embryonic cells?
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neural crest cells
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T cells proliferate and differentiate (or are destroyed) in what portion of the thymus?
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Cortex
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Reticular stroma of thymus formed by ____ cells
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Reticular stroma of thymus formed by EPITHELIORETICULAR cells
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Are the thymus reticular stroma constructed with reticular protein fibers?
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NO
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Which cells isolate the thymus cortex from the medulla?
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epithelioreticular cells
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T cells are called _____ while they are developing in the thymus
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thymocytes
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T cells actively divide in the ____ cortex of the thymus and migrate toward the ___ cortex as they become immunocompetent
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T cells actively divide in the OUTER cortex of the thymus and migrate toward the INNER cortex as they become immunocompetent
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Where in the thymus are macrophages found?
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both cortex and medulla
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Macrophages destroy more than 90% of the lymphocytes in the _____ region of the thymus
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CORTEX
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Where are Thymic (Hassall's) corpuscles found?
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thymic medulla
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what are thymic (Hassall's) corpuscles?
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concentric whorls of epithelioreticular cells, some keratinized
may be source of thymic hormones |
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Arterial blood sources for thymus
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anterial intercostal aa
internal thoracic (mammary) aa |
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where do arterioles enter the thymus
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cortico-medullary junction
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Venous drainage of thymus
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L. brachiocephalic v
internal thoracic vv inferior thyroid vv |
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Function of blood-thymus barrier
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protects developing naive lymphocytes in the thymus from being confused by circulating antigens
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4 major structural layers of blood-thymus barrier, from lumen outward:
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4 major structural layers of blood-thymus barrier, from lumen outward:
continuous epithelium w/ occluding jxns of capillaries resident macrophages within perivascular CT basal lamina of epithelioretiular cells epithelioreticular cells w/ occluding junctions |
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Histological changes in thymus with age (4):
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loss of lymphocytes
increase in adipose tissue increase in number and size of thymic corpuscles tissue stroma may collapse |
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at what age is thymus at maximum size?
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puberty
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functional regions of thymus being to decline in year ____
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1
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Where are lymph nodes found in groups (4 places)
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neck
axilla inguinal region major arteries |
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Nodes are arranged in ____
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series
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3 major functions of lymph nodes
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phagocytosis of foreign material
activation of lymphocytes recirculation of lymphocytes |
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Types of APCs in lymph nodes
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dendritic follicular cells
macrophages |
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Within lymph nodes ____ carry lymph through the node
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multibranched sinuses
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2 regions of lymph node interior
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cortex
medulla |
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Where in lymph node are B cells found
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cortex
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Where in lymph node are T cells found?
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medulla
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What are lymphoid nodules?
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spherical aggregates of B cells in node cortex
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Primary lymphoid nodules contain
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naive B cells
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Secondary lymphoid nodules contain
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activated B cells
interior = germinal center |
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Where are dendritic follicular cells found in the lymph node cortex
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germinal center
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Where are APCs found in the lymph node?
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both cortex and medulla
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Medullary cords are primarily ___, ___ and _____
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B cells, plasma cells and macrophages
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Function of lymph node sinusoids
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trap material cells, etc. entering lymphatics in peripheral tissue
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sentinal nodes
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first node in the series to drain a given region of the tissue
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Where do blood vessels enter and exit the lymph nodes?
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at the hilum
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Capillary networks in the lymph node ____
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cortex
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Postcapillary venules in the lymph node ___
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paracortex
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Specialized cuboidal endothelium in paracortex venules express high levels of ____
These venules are called ____ |
CAMs
HEVs |
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Extravasation =
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exit by diapedesis btw endothelial cells
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Lymphocytes entering nodes via lymph enter through
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afferent lymphatics
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lymphocytes entering nodes via the blood enter through
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HEVs
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What type of lymphocytes can enter/exit nodes freely?
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naive lymphocytes
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Once activated, peripheral APCs migrate to the ____ and ____ regions of the lymph nodes
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superficial and paracortex regions
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Lymph nodes become palpable when...
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infection causes lymphocyte proliferation in nodes, causing the surrounding tissue to swell
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Plasma cells may reside in ____
or may enter the ____ and ____ |
Plasma cells may reside in teh medullary cords and sinuses and release Abs into lymph
May also enter sinuses and exit node |
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Function of SPLEEN
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filter blood
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largest lymph organ
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spleen
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Immune system function of spleen occur in the _____region
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white pulp
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4 immune system functions carried out by spleen
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Ag presentation by DCs and Mphages
Activation and prolif of B and T cells Production of Ab's Removal of antigen molecules from blood |
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Hemopoietic functions of spleen (4)
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removal and destruction of old/damaged RBCs, platelets
formation of bilirubin iron scavenging formation of RBCs in early fetal life |
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Blood vessels enter/exit spleen via its _____
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trabeculae
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Proportion of spleen volume = white pulp
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25% white pulp
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What is splenic white pulp
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densely packed, cylindrical aggregates of lymphocytes and APCs surrounding small arteries
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2 main regions of white pulp
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Periarterial lymphatic sheath (PALS)
Lymphoid nodules |
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enlarged lymphoid nodules in spleen -
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Malphigan corpuscles
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type of lymphocyte found in PALS
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T lymphocytes (arr. around central artery)
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type of lymphocyte found in lymphoid nodules
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B cells
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marginal zone of spleen
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cords of cells and narrow sinuses lying on outer margin of white pulp
primary site for Ag trapping and presentation |
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Where do B and T cells exit the circulation and travel to their respective areas of white pulp?
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marginal zone of spleen
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splenic cords
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loose framework of reticular fibers and cells (e.g.: lymphocytes and Mphages)
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splenic sinuses
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wide channels for slow blood flow
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cell surface markers of normal RBCs
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CD47
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Splenic blood flow sequence
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see CP p. 21
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MALT includes...
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loose lymphocytes
plasma cells lymphatic nodules in mucosa |
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MALT is found in the (4 places) ...
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alimentary tract
respiratory tract UG tract oral cavity |
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Is MALT encapsulated?
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NO
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Additional role of MALT specific to gut
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suppressing immune functions
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Aggregates of MALT lymphoid nodules (3)
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Peyer's patches (ileum)
Tonsils (palatine, lingual, pharyngeal) Vermiform appendix |
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BALT
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bronchi associated lymphatic tissue
isolated nodules at branches in tracheobranchial tree |
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GALT
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gut associated lymphatic tissue
esp. in colon, rectum |
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3 regions within peyer's patches
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lymphoid nodules (B cells)
T cell region Follicle-Associated Epithelium (FAE) |
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Type of specialized cell found in Follicle associated epithelium
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Microfold cells (M cells)
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What kind of cells are M cells
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APCs
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M cells are specialized for what function?
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transcytosis
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Type of cell possibly responsible for establishing immune tolerance to non-pathological foods and commensal microorganisms
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M cells in peyer's patches
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What type of Ig do plasma cells in Peyer's patches secrete?
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IgA
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Tonsils
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See CP p. 24
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