Exam 3: Lymphatic System Flashcards
What lymphatic organ is only in ruminants?
Hemal (lymph) nodes
What lymphatic organ is only in avians?
Cloacal Bursa
How many lymph nodes do Avians have?
few to none
What are the 3 functions of the Lymphatic System?
- Protect from endogenous/exogenous substances
2.Primary defense system
3.Secondary defense system
How does the Lymphatic System function as a Primary Defense System?
Epithelial barriers prevent exogenous substances from getting in
Gives examples of the epithelial barriers in the lymphatic primary defense system
Skin (epidermis)
CT of skin (dermis)
Epithelial lining of GI, resp, urogenital
What is the Lymphatic System’s Secondary Defense System?
Lymphatic / Immune System
kicks in if substances get past primary defense
Which embryonic tissue are most lymphatic structures derived from?
Mesoderm
What lymphatic structure is derived from endoderm?
Epithelial Reticular Cells
Lymphocyte function
immune response
Immunocompotent
lymphocytes “remember problem”
leads to stronger effect next time
Antigen
substance that causes immune response
Examples of antigens
bacteria, virus, toxin, tumor cells
What are the 2 types of lymphocytes?
T cells
B cells
What lymphatic structure are T cells modified by?
Thymus
What is the function of T cells?
cell-mediated immune response
What occurs when T cells contact an antigen?
Produces lymphokines
lead to cell membrane lysing –> death
What lymphatic structure are B cells modified by in birds?
Cloacal Bursa
What 2 lymphatic structures are B cells modified by in mammals?
bone marrow
Ileal Peyer’s Patch
What is the function of B cells?
humoral immune response
Where do lymphocytes go after development?
secondary lymphatic organs
(lymph nodes, spleen, tonsils)
Primary/Central Lymphatic Organs of Avians
Thymus
Cloacal Bursa
Primary/Central Lymphatic Organs of Mammals
Thymus
Bone Marrow
Ileal Peyer’s Patch
What is special about the development of lymphocytes in primary lymphatic organs?
Shielded from outside antigens
so don’t recognize bad things as normal
Examples of Secondary/Peripheral Lymphatic Organs
lymph nodes, spleen, tonsils
What are four cell types that are normally in every secondary lymphatic organ?
plasma cells
macrophages
reticular cells
lymphocytes
Stroma
network of reticular cells + reticular fibers in lymphatic organs
“supportive framework”
Reticular Cells
specialized fibroblasts that produce reticular fibers
Involution
concept that thymus gets smaller over time/with age b/c fewer cells
What are the functions of the thymus?
T cell production
Humoral factors
What are two humoral factors in the thymus?
Thymosin
Thymopoietin
What is the function of humoral factors in the thymus?
stimulate bone marrow stem cells –> T cells
Septa
sheet of tissue
make up capsule of thymus
Thymus has (complete/incomplete) lobules
incomplete lobules
What are the two parts of a thymic lobule?
Cortex (outer/darker)
Medulla (inner/lighter)
List the structures in the cortex/medulla of thymus
T cells
Macrophages
Stroma (with epithelial reticular cells)
Thymic (Hassall’s) Corpuscles
Are there more T cells in the cortex or medulla of the thymic lobules?
Cortex - because they are leaving!
Epithelial Reticular Cells
cells in stroma of thymic lobules
connected by desmosomes
surround T cells
What is the function of epithelial reticular cells?
produce thymopoietin to influence T cell development
Are there reticular fibers in the stroma of the thymic lobules?
NO
Thymic (Hassall’s) Corpuscles
laminated masses of epithelial reticular cells
unknown function
Larger = older animal
What two structures are characteristic of the Avian Thymus?
Thymic Corpuscles
Myoid Cells
What is different about Thymic Corpuscles in the Avian compared to mammals?
“loose” aggregates of epithelial reticular cells
NOT tightly adhered
Myoid Cells
in medulla of thymic lobule
unknown function
look like skeletal muscle in cross-section
What kind of capillaries are in the cortex of the thymus and what do they have?
continuous cortical capillaries
have blood-thymus barrier
What allows the thymus to shield developing T lymphocytes?
Blood-Thymus Barrier
List Layers of Blood-Thymus Barrier
capillary endothelium
basement membrane
connective tissue
basement membrane
epithelial reticular cells
Lymph Vessels are ONLY (Afferent/Efferent)
Efferent
Cloaca
common chamber where GI, repro, urinary tracts empty in avians
What is the function of the Cloacal Bursa?
development of B lymphocytes
What are the “folds” within the Cloacal Bursa?
Plicae
What is the term for the cortex + medulla in the Cloacal Bursa?
Follicles
Does diffuse lymphatic tissue encounter antigens or not?
No recent antigen encounter, waiting to respond
Primary Nodule
no germinal/active center
even texture, small lymphocytes
Secondary Nodule
responds to antigen
germinal center (immature center where lymphocytes react to antigen)
corona (darker, outer ring)
Peyer’s Patch
aka mucosal aggregated lymphatic nodules
have pseudovilli domes
Ileal Peyer’s Patch
in ileum of ruminants
primary lymphatic organ in ruminants
ONLY developing B cells
What lymphocytes are in tonsils and are they in contact or independent of antigens?
T & B cells
contact antigens
Fossula
depressions in tonsil
Crypt
openings on tonsil after fossula
Follicle (or Tonsil)
= fossula + crypt
List 3 types of tonsils
Palatine
Pharyngeal
Lingual
What tissue type is palatine tonsil covered by?
Non-Keratinized Stratified Squamous Epithelium
Where are palatine tonsils located?
oral part of pharynx (dog)
What tissue type covers the pharyngeal tonsils?
Pseudostratified Columnar Epithelium w/ cilia
What is the location of the pharyngeal tonsils?
nasal part of pharynx
What tissue type covers the lingual tonsils?
Keratinized Stratified Squamous Epithelium
Where are lingual tonsils located?
root of tongue
Where is tubal tonsil located?
nasopharynx where auditory tube goes
What is lymph?
fluid that leaks into interstitial spaces
Which 3 structures have no lymph?
brain
spinal cord
retina of eye
Name 2 ducts in the lymph vessel system
Thoracic duct
Right Lymphatic duct
Lymph Nodes are (primary/secondary) lymphatic organs
secondary
What are the two functions of lymph nodes?
Filter lymph
Immune response
What is different about swine lymph nodes?
Opposite lymph flow
flows from center –> periphery
What 2 tissue types are lymph node capsules made of?
DICCT or Loose CT
What is the term for spicules/indentations of capsule into the lymph node?
Trabeculae
Apart from cortex/medulla, what other layer is in the lymph node?
Paracortex
What the paracortex of the lymph node?
area of more distributed T cells
What are two unique structures in the medulla of the lymph node?
medullary cord
medullary sinuses
What is present in the medulla cord of the lymph node?
lots of plasma cells
What is the medullary sinus in the lymph node?
space between cords where lymph is located
What is the hilus of the lymph node
indentation where vessels come & leave
Explain lymph flow in a lymph node
afferent lymph nodes –> subscapular sinus –> cortical sinus –> medullary sinuses –> efferent lymph node
What causes enlargement of lymph nodes?
proliferation of T & B cells during infection
What is different about equine lymph nodes?
have many, smaller lymph nodes
What is the only lobulated lymphatic organ?
thymus
(T/F) The thymus has lymphatic nodules.
False
What are areas in the Peyer’s Patch with T cells called?
Thymus-dependent zones
Where are M cells located?
Peyer’s Patch (aggregated lymphatic nodules)
What is the function of M cells?
“sampling” antigens from lumen selectively for lymphocytes to test
Which lymphatic organ is the only one which afferent lymph vessels?
lymph node
What are the sinuses in the lymph node lined by? What is unique about them for their function?
endothelium
big gaps so lymph percolates
Paracortex (thymus-dependent zone)
region where cortex is continuous with medulla and T cells predominate
What is the function of reticular cells in lymph node?
span sinuses to slow lymph flow and divert it to contact other cells within lymph node
What do macrophages contain in lymph nodes on occasion?
hemosiderin
What is hemosiderin?
product of hemoglobin broken down by macrophages in lymph nodes (recycled RBC)
What kind of tissue surrounds the lymph node (outside capsule)? And what structures are within it?
adipose tissue
lymph vessels
Foreign Body Giant Cells
multinucleated, pale-staining macrophages in lymph node that ingest foreign material
What is significant about plasma cells near foreign body giant cells?
negative golgi image
basophilic cytoplasm
What type of animals are Hemal Nodes found in?
ruminants only
Hemal nodes have _____ instead of lymph vessels.
RBC | large blood supply
What two types of tissue make up the hemal node capsule?
DICCT + smooth muscle
Function of lymph node
“surveillance system”
filters/monitors what’s in lymph before going back into vasculature
Where are hemal nodes located?
any place where lymph nodes are
most common- paralumbar fossa
(T/F) Hemal Nodes have lymphatic nodules
True
1-2 scattered nodules
Function of Hemal Nodes
filter blood
immune response to antigen in blood
(T/F) Hemal Nodes have a cortex and medulla
False
only lymphatic nodules, not organized into cortex/medulla
What are the 3 functions of the spleen?
Produce blood cells in embryo
RBC/platelet reservoir
Blood filter
The spleen is a (primary/secondary) lymphatic organ that is (independent/dependent) of antigen.
Secondary
Dependent
How is the spleen filter blood? (2 ways)
destroy old RBC (recovery iron)
immune response (T + B cells)
What structure covers the spleen?
tunica serosa
What’s another name for tunica serosa on spleen?
visceral peritoneum
What two layers is the tunica serosa of the spleen made up of?
mesothelium + lamina propria (CT layer)
What two tissues is the capsule of spleen made of?
DICCT + smooth muscle
White pulp of spleen
where lymphocytes are
periarterial lymphatic sheath
(where T cells are) where T cells infiltrate artery/arteriole in spleen
Red pulp
everything around white pulp in spleen
Splenic Cords
everything between venous sinuses in the red pulp of the spleen
Venous sinuses
spaces in red pulp
Marginal Zone
junction of red & white pulp in spleen
Function of Marginal Zone in spleen
where blood flow slows so T & B cells can contact antigen in white pulp
Where does antigen-cell interaction take place in spleen?
marginal zone
What two cell types are in the marginal zone?
macrophages + lymphocytes
Order of Splenic Circulation
aorta –> celiac A –> splenic A –> trabecular A –> artery of the white pulp
Which lymphocyte dominates in the white pulp?
B cells
(T/F) The spleen has lymphatic nodules.
True
Once the splenic artery branches, it becomes ______ artery.
trabecular
Open theory
blood enters right into splenic cord from terminal capillaries and blood percolates to get to venous sinuses
Closed theory
terminal capillaries empty directly into venous sinuses
Fusiform Endothelial Cells
very long endothelial cells lining of venous sinuses with gaps so RBC can get into venous side of circulation
The spleen has only (afferent/efferent) lymph vessels. It (receives/produces) lymph.
efferent
produces
Differences in avian spleen
no lymphatic nodules form (unless diseased state)
What two cell types are present in the splenic cord?
plasma cells + macrophages
What occurs in the spleen when B lymphocytes are stimulated?
nodules form
What occurs in the spleen when T lymphocytes are stimulated?
thickening of periarterial lymphatic sheath (where T cells predominate)
(T/F) Macrophages are immunocompetent (can remember).
False
Arterial Penicillus
terminal portion / branching from artery of the white pulp
Ellipsoid (sheathed capillary)
reticular cells + macrophages
RBC forced through space between and pulls out anything abnormal for macrophages to degrade
Thick smooth muscle in capsule + trabeculae contracted indicates the ______ theory.
closed (because so close to venous sinuses)
When smooth muscle in capsule + trabeculae is relaxed, this indicates ____ theory.
closed (percolates b/c further from venous sinuses)
Annular Reticular Fibers
supportive fibers that surround fusiform endothelial cells in venous sinus
What cell type is in the venous sinuses that help degrade RBC if they cannot get through the fusiform endothelial cell gaps?
macrophages
Venous side of circulation in spleen (mechanism of movement)
red pulp vein –> trabecular vein –> splenic vein –> portal vein to liver
Sinusal vs. Nonsinusal Spleen
smooth muscle in sinuses in ruminants = not technically sinusal so NONSINUSAL
What is different about the avian spleen?
on right side of stomach
NO lymphatic nodules or trabeculae from capsule
ellipsoid has simple cuboidal lining
Mononuclear phagocytes
phagocytic cell with consistently shaped nucleus
Polymorphonuclear Phagocytes
= neutrophil | many forms of the nucleus
Mononuclear Phagocytes
macrophages (have consistently shaped nucleus
Two cell times that derived from the monocyte-macrophage system
mononuclear phagocytes
polymorphonuclear
Monocytes derive sinus-associated cells which can differentiate into what 4 types of macrophages?
splenic
lymph node
bone marrow
liver
Monocytes derive into what 4 cell groups?
Sinus-associated cells
Free cells
Antigen processing cells
Tissue cells
What 2 macrophages types arise from “free cell” lineage of monocyte?
Serous membrane
alveolar
What cells arise from antigen processing cells from monocyte lineage? (5)
M cells
interdigitating cells
follicular dendritic cells
reticular dendritic cells
veiled cells
What 4 cell types derive from tissue cell category of monocyte lineage?
connective tissue macrophages
mesangial cells (kidney)
microglia (CNS)
osteoclasts
Term for elevation in monocytes
Monocytosis
Dendritic cells
“tree-like” branching dendritic processes
Dendritic cell functions (2)
-bind antigen on surface
-retain antigens for long periods
Follicular dendritic cells location
B cells areas (germinal centers)
Interdigitating cells location
T cell areas (proliferating)
Veiled cells location
afferent lymph vessels + sinuses of lymph nodes
Reticular dendritic cells (“clear cells” or Langerhans) location
stratified epithelia
M cell location
aggregated lymphatic nodules (Peyer’s patches) + tonsils
M cell function
upside-down cup open to lymphocyte/macrophages and bring antigens in for “sampling”
T cells make up __% circulating lymphocytes in blood, B cells __% and the other __% are made up by ___.
70
20
Natural Killer (NK) cells
Natural Killer (NK) Cell Function
recognize body’s own cells that become tumors / abnormal growth
produce chemicals similar to T cells
(T/F) NK Cells are immunocompetent.
False
What is prominent in NK cells?
azurophilic granules on the lymphocyte
Killer (cytotoxic) T cells
produce lymphokines when in contact with antigen (destroy abnormal cells)
T cell reverts into ________ when it comes into contact with antigen and becomes _______.
Lymphoblast
immature
List the 4 “clones” a lymphoblast divides into.
Killer (cytotoxic) T cell
T memory cell
Helper T cell
Suppressor T cell
T memory cells
recognize antigen so when encountered again, faster/greater response at next encounter
Helper T cells
help B cells when they encounter antigen
Suppressor T cell
make chemical suppressor substances which keep immune system from going overboard and harming body
Blast transformation
when T & B lymphocytes undergo process back to immature form when encounter antigen
B cells when encounter antigen form what 2 cell “clone” types?
plasma cells
B memory cells
B memory cells
remember antigen, faster/greater response
Lymphocytopoiesis
process of lymphoblast to get progressively smaller
Antigenic/immunological surveillance
circulation and recirculation allow lymphocytes to go anywhere in body
“lymphocyte patrol”
