Lectures 46 & 47: Lymphatic Microanatomy Flashcards
4 body compartments
blood vessel/blood
interstitial space/fluid
intracellular space/cytoplasm
lymphatic vessel/lymph
when is lymph called lymph
once interstitial fluid is in lymphatic vessels
lymphatic capillaries : features and function
thin walls
begin as networks of blind capillaries
collect interstitial fluid with large molecules, including antigens and cells
lymphatic collecting vessels
formed from lymphatic capillaries
contain valves
unite to form major trunks/ducts
lymph nodes function
filter lymph
what do collecting lymphatic vessels have to go through before reaching venous system
lymph node
afferent lymph vessel: definitin
bring lymph into the node
cisterna chyli: function
store lymph
thoracic duct: definition/location
extension of cisterna chyli into thoracic cavity
runs between azygous vein and aorta
where does hematopoiesis take place
bone marrow
2 progenitors from hematopoietic stem cells
common myeloid
common lymphoid
common myeloid progenitor cells (5)
basophils/mast cells
eosinophils
neutrophils
monocytes –> macrophages
common lymphoid progenitor cells (3)
T lymphocytes
B lymphocytes
natural killer cells
which cells are part of the innate immune response (6)
basophils
eosinophil
neutrophil
macrophages
dendritic cells
**natural killer cells
which cell stems from lymphoid progenitor but has innate immune properties
natural killer cells
2 cells that are part of adaptive immune response
T lymphocytes
B lymphocytes
2 types of antigen presenting cells (categories)
antigen presenting (activated)
professional antigen presenting
innate immune response
no requirement for previous antigen exposure
non specific
immediate/rapid
1st line of defense
triggered by binding of antigens to receptor
adaptive immune response
recognize diverse antigens
delayed response at 1st antigen then response is quicker
lymphocytes
what kind of cells are dendritic cells
professional antigen presenting cells
dendritic cells function
activate B lymphocytes
2 professional antigen presenting cells
dendritic cells
macrophages
what triggers the innate immune reponse
antigens bind to receptor
innate immune cells functions (4)
phagocytize pathogens
secrete proteins with antimicrobial effect
secrete cytokines to recruit other cells of immune system
2 types of lymphocytes
T
B
2 subtypes of T lymphocytes
cytotoxic
helper
cytotoxic t cells are activated by
antigens conjugated to MHC I in antigen presenting cells
helper t cells are activated by
MHC II in professional antigen presenting cells
T lymphocytes site of generation vs differentiation
generated = bone marrow
differentiated = thymus
which cells are involved in cell mediated immune response
t lymphocytes
which cells are involved in humoral immune response
b lymphocytes
what kind of receptor do T cells have
T cell receptor
what kind of receptor do B cells have
B cell receptor
what activates B lymphocytes
directly by antigens and professional antigen presenting cells (dendritic cells, macrophages)
unique function of B lymphocytes
only nonmyeloid cell that can function as antigen presenting cells to activate T lymphocytes
natural killer cells: function
innate immune response
respond to kill cells like cytotoxic t cells
what are natural killer cells activated by
by antigen directly
cells covered with antibodies
cells without MHC
what does MHC stand for
major histocompatibility complex
what can act as an antigen presenting cell
any type of infected cell
cytotoxic t cells functions
destroy infected cells and pathogens (apoptosis or lysis)
secrete proteins that create channels of the cell’s plasma membrane and induce fragmentation of DNA
helper t cells function
secrete cytokines that enable/help activation of B lymphocytes and cytotoxic t cells
CD8+ are what kind of t cells
cytotoxic t cells
CD4+ are what kind of t cells
helper t cells
2 subtypes of B lymphocytes
plasma cells
memory b cells
plasma cells
secrete antibodies
memory b cells
plasma cells that remain in body and respond more quickly during next encounter with antigen
primary lymphoid organs (2)
bone marrow
thymus
where do immune cells develop
primary lymphoid organs = bone marrow and thymus
where does most of immune response initiated/executed
secondary lymphoid organs
secondary lymphoid organs (3)
lymph nodes
spleen
lymphoid tissue
Bone marrow functions/process that occurs
Hematopoiesis —> produces generic form of lymphocytes from lymphoid lineage
-produce lymphocytes B
Bone marrow: parenchyma (2 cells)
Hematopoietic stem cells
Differentiating HSCs —> myeloid and lymphoid progenitors
Bone marrow: stroma (3 cell types)
Reticular cells from mesenchymal origin
Reticular fibers (type II collagen)
Adipocytes
Perivascular cells (2)
Macrophages and pericytes
What are pericytes
Niche cells that form the mesh work of the stroma
What happens to bone marrow with age (what replaces it)
Adipocytes replace 50% of bone marrow
Hematopoiesis decreases
Blood sinusoids are the site of
Cellular and molecular exchange between circulation and hematopoietic compartment
What are sinusoids
In bone marrow
Venous capillaries —> where arterial capillaries and venules meet
What kind of capillaries are sinusoids
Fenestrated
Thymus function
Site of education and differentiation of T lymphocytes
What happens to thymus during puberty
Atrophies/gets smaller
Thymus: stroma
Connective tissue
Contains blood vessels, efferent lymphatic vessels and nerves
Trabeculae of thymus
Divides parenchyma into incomplete lobes which unite at center
3 regions of thymus parenchyma
Cortex
Corticomedullary junction
Medulla
Epithelioreticular cells: definition
Specialized cells within thymus cortex
Have features of both epithelial and reticular cells
Contribute to form a framework
Where are epithelioreticular cells found
Cortex of thymus
Thymus cortex: contents (4)
Closely packed developing T lymphocytes
Epithelioreticular cells
Macrophages
Blood thymus barrier
Epithelioreticular cells: function
Work as stroma —> network
Create micro environment for lymphocyte T education
Macrophages in thymus cortex
Phagocytize lymphocytes that don’t fulfill thymus education requirements
Where is the blood thymus barrier located
Cortex of thymus
Blood thymus barrier: formed by, functions
Formed by wall of blood vessels
Prevent T lymphocytes from contacting antigens
Clean environment for education -> SHIELD
5 layers of blood thymus barrier
Blood vessel endothelium
Basal lamina
Macrophages
Basal lamina
Epithelial reticular cells
Basal lamina of blood thymus barrier is made of what type of cells
Epithelial reticular cells
What cells are the corticomedullary junction made of
Epithelioreticular cells
Corticomedullary junction: function
Form barrier between cortex and medulla
Corticomedullary junction contains
Blood vessels - arterioles and venules
High endothelial venule
High endothelial venule definition/function/location
Specialized post capillary venule
Contains epithelial cells and lymphocytes
Diapedesis and recirculation (of lymphocytes)
Site for entrance and exit of lymphocytes
Found in lymphoid organs except spleen
Inside Corticomedullary junction
What cells facilitate the movement of T lymphocytes in high endothelial venule
Epithelial cells
Type of epithelium in epithelial cells: high endothelial venule
Simple cuboidal
Thymus medulla: contents
Loosely packed MATURE lymphocytes
Extensive mesh work of epithelioreticular cells
Thymic/hassall’s corpuscles
Thymic/hassall’s corpuscles: definition/function/location
Epithelioreticular cells concentrically arranged with flat nuclei
Involved in thymus differentiation and education of T lymphocytes
In thymus medulla
Where does education and final differentiation of lymphocytes T occur
Thymus (cortex or medulla)
Pre lymphocytes T are selected into ________ by _______
Functional T cells
Pass through cortex and medulla
2 locations lymphocytes can be selected in
Cortex
Medulla
Lymphocytes selected in cortex based on
Affinity to bind major histocompatibility complex
Positive selection: definition/location
Cortex of thymus.
Lymphocytes that don’t bind to MHC are induced to die
Lymphocytes are selected in medulla based on
Affinity to bind tissue specific antigens
Negative selection: definition/location/result
Medulla of thymus
Lymphocytes that bind with too strong affinity to tissue specific antigens are induced to die
results in Group of lymphocytes that bind to MHC only when they are conjugated to foreign antigens
Process of T lymphocyte education and differentiation in thymus (3)
Lymphocytes selected in cortex
Lymphocytes selected in medulla
Selected lymphocytes differentiate into T helper or cytotoxic T cells —> leave medulla through high endothelial venules
Flow of lymphocytes in thymus: general
Pre lymphocyte T travels through capillary —> selected lymphocyte T based on binding to MHC in capillary —> selected lymphocyte T based on binding to tissue specific antigen leaves capillary —> moves through vein (HEV)
Lymph nodes definition and function
Encapsulated lymphatic organs that are interposed among lymphatic vessels
Filters lymph on its way to blood vascular system
3 components of lymph node stroma
Capsule
Trabeculae
Reticular tissue
Capsule and Trabeculae are made of what kind of tissue: lymph node stroma
Dense connective tissue
Capsule vs Trabeculae: lymph node stroma
Capsule extends as Trabeculae
Trabeculae = forms framework
Reticular tissue in lymph node stroma: components and function
Reticular cells and reticular fibers
Form supporting mesh work —-> mechanical filter
Cells contained within parenchyma of lymph node (4)
Lymphocytes T
Lymphocytes B
Dendritic cells
Macrophages
What kind of arrangement are T/B lymphocytes, macrophages and dendritic cells in within parenchyma of lymph node
Unchallenged
Challenged arrangement of lymph node parenchyma (3 layers)
Superficial cortex
Deep cortex medulla
Primary nodules in superficial cortex of lymph node
Aggregates of B lymphocytes (not activated)
What cells make up the germinal center of lymph node
Plasma cells
2 cells within secondary nodules: lymph node
B lymphocytes
Plasma cells
2 zones/centers within secondary nodules: lymph node
Corona/mantle zone
Germinal center
What cells are contained within the corona/mantle zone of secondary modules: lymph node
B lymphocytes
What cells surround nodules to help activate B lymphocytes into plasma cells
T helper cells
Deep cortex of lymph node: 2 cell types located here
Most T lymphocytes
Dendritic cells
Parenchyma in lymph node forms
Medullary cords
Medullary cords: location, contents/cells
In medulla of lymph node
Lymphocytes B, macrophages, plasma cells, dendritic cells
Medullary cords are separated by
Medullary sinuses
Flow of lymph and blood into node (5)
Lymph enters afferent lymphatic vessel—> subscapular sinus —> trabecular sinus —> medullary sinus -> lymph leaves via efferent lymphatic vessel
Sinuses in lymph node: function
Allow lymph to percolate freely into superficial and deep cortex so Lymphocytes engage with antigens
Flow of lymphocytes into lymph node (9)
B and T cells in artery —> enter node at high endothelial venule —> T cells stay in deep cortex —> B cells are pushed to superficial cortex —> APC activates T helper cells —> T helper cells activate B lymphocytes —> plasma cells from in secondary nodule —> plasma cells go to medullary sinus —> plasma cells and other lymphocytes exit in efferent vessel
Spleen: main function
Filter blood
What do Trabeculae and capsule contain: stroma of spleen
Myoblasts
Myoblasts function: spleen stroma
Discharge RBCs into blood
2 regions of spleen parenchyma
White pulp
Red pulp
White pulp (general): spleen
Parenchyma
Lymphoid nodules randomly scattered
Secondary lymphoid organ
Red pulp (general): spleen
Parenchyma
Embeds white pulp and contains splenic sinuses
Periarterial lymphatic sheath: definition/components/location
White pulp of spleen
Aggregates of T helper lymphocytes around central artery
What forms the central artery: white pulp of spleen
Trabecular arteries branched into white pulp
what are lymphatic nodules in white pulp
localized expansion of periarterial sheath
lymphocytes B surrounded by lymphocytes T
3 stages of lymphatic nodule formation (General): spleen
resting white pulp
primary nodule
secondary nodule
resting white pulp: lymphatic nodule formation
antigen presenting cells (macrophages) activate T helper lymphocytes in periarterial sheath
primary nodule: lymphatic nodule formation
T helper lymphocytes activate lymphocytes B
B cells expand and push periarterial sheath to the side
secondary nodule: lymphatic nodule formation
lymphocytes B proliferate to form plasma and memory cells –> go into blood
2 regions of red pulp: spleen
splenic cords
splenic sinuses
cells that reside in splenic cords (4)
erythrocytes macrophages
dendritic cells
plasma cells
megarkaryocytes
splenic sinuses: definition/function
spaces lined by endothelial cells
macrophages extend between endothelial cells to monitor antigens in blood
blood supply to spleen (main)
splenic artery
what kind of circulation type do dogs have
closed
closed circulation
only filtering occurs in sinuses (no filtration in splenic cords)
splenic circulation within red pulp
splenic artery –> trabecular arteries –> central arterioles –> dump blood into splenic sinuses
venous drainage from red pulp
trabecular veins –> splenic vein
different types of lymphoid tissue: function
intercept antigens and initiate immune response
2 examples/types of mucosa associated lymphatic tissue
GALT
bronchus associated lymphatic tissue
characteristics of lymphoid tissue: structures lacking, composition, function
no cortex or medulla
made of randomly packed lymphocytes
after contact with antigen: travel to regional lymph nodes for proliferation/differentiation
progency of proliferated/differentiated lymphocytes in MALT return to where
lamina propria as effector T cells and B eclls
lymphatic nodules aka
lymphatic follicles
2 regions within lymphatic nodules/follicles
germinal center
mantle zone/corona
cells within germinal center: lymphatic nodule
dendritic cells
B cells
what is the mantle zone of lymphatic nodule
outer ring of lymphocytes
which region of lymphatic nodule indicates response to antigen
germinal center
3 examples of lymphatic nodules
peyers patches in ileum
tonsils
vermiform appendix
