Lymphatic Tissue Flashcards
What are the two primary lymphatic tissues? What characteristic distinguishes them?
Bone marrow
Thymus
Site of development and maturation of lymphocytes into immunocompetent cells
What are the three secondary lymphatic tissues?
- Lymph nodes
- Mucosa-associated lymphatic tissue (MALT)
- Spleen
What are the four subtypes of mucosa-associated lymphatic tissue?
- GALT (gut associated)
- BALT (bronchus)
- GU tract
- Tonsils
What is the defining characteristic of secondary lymphatic tissue?
Site of formation of immunological defense against antigens or pathogens
Confrontation with antigens or pathogens occurs here
What part of the lymph system filters lymph?
Lymph nodes
What part of the lymph system filters blood??
Spleen
What part of the lymph system acts as surveillance?
MALT
Where does confrontation of antigens occur?
In secondary lymphatic tissues
Where is GALT found?
In the lamina propria of the intestines
Where are the mucous-associated lymphatic tissues found within the body?
Sprinkled in loose CT as part of another organ, usually in the lamina propria
What type of cells are present in lymphatic tissue?
Lymphocytes
Monocytes
Macrophages
Plasma cells
What type of fibers are present in lymphatic tissue?
Reticular fibers
What are the histological characterisitcs of primary lymphatic nodules?
appears homogenous throughout, has mostly small lymphocytes
What are the histological characterisitcs of secondary lymphatic nodules?
Has a corona zone and a germinal center
What distinguishes between primary and secondary lumphatic nodules?
Appearance
What is the corona zone in secondary lymphatic tissue?
the outer, dark-staining zone, containing mature lymphocytes
What is the germinal center of secondary lymphatic nodules?
The inner, light-straining zone containing immature lymphocytes
Encounter with an antigen has what effect on the germinal centers of secondary lymphocytes?
Causes the center to swell
What helps suspend cells in primary lymphatic nodules?
Reticular fibers
When there is a clear differentiation in the mantle zone and the germinal center of secondary lymphatic nodules, what has occurred?
Anitgen is/was present
What processes are taking place in the germinal center of secondary lymphatic nodules?
Mitosis
What type of cells are in the mantle zone of secondary lymphatic nodules?
Mature lymphocytes
What are the two forms that lymphatic nodules may appear as? How long do each last (relatively)?
Solitary lymph nodes are short lived
Aggregates of lymph nodes are permanent
What are the four examples of lymphatic node aggregates that were discussed in class?
Peyer’s patches
Lymphatic tissue in appendix
BALT in respiratory tract
Lymphatic nodules in the tonsils lymph nodes, and spleen
What are Peyer’s patches? Where are they found? What do they contain?
Lymph node aggregates in the ileum that contains B and T lymphocytes
What do the lymphatic tissue in the appendix contain? Where are these found in the layers of the tissue?
Consists of permanent aggregations of lymphatic nodules
in the lamina propria and the submucosa of the appendix
The lymphatic nodules present in the tonsils, lymph nodes, and spleen are of what type?
Lymphatic aggregates
What type of lymph tissue is found in the appendix?
Primary lymphatic nodule aggregates
The pharyngeal, palatine, and lingual tonsils are aggregations of what? What cells do they contain?
Lymphatic nodules, containing B lymphocytes
What is characteristic of the CT of the tonsils? What is the purpose of this?
Thay have partial / incomplete CT capsule which sends septa into the interior of the tonsil.
Capsule may provide some protection from spread of tonsilar infections
What is the epithelial type that surround the pharyengeal tonsils?
Pseudostratified columnar
What is the epithelial type that surround the lingual tonsils?
Stratified squamous (non-keratinized)
What is the epithelial type that surround the palatine tonsils? What infiltrates this?
Stratified squamous (non-keratinized), infiltrated by B lymphocytes
What are the epithelial lined pits that are present in palatine tonsils?
Crypts
What surrounds the palatine tonsils on the non-luminal side?
Cap
What do the palatine tonsils contain? What is the purpose of these?
lymphatic nodules where B-lymphocytes are produced
What type of epithelium covers the pharyngeal tonsil? What specialization does the epithelium have?
Pseudostratified columnar with cilia
What forms the white exudate found in viral tonsillitis?
WBCs
Adenoid tonsils is to (insert word here) as pharyngeal tonsils is to crypts.
Pleats
What are the only organs that are located along the path of a lymphatic vessel?
Lymph nodes
What is the function of lymph nodes?
Filter lymph prior to being passed on to the bloodstream
What covers lymph nodes? What is this made of?
A capsule formed by dense CT
What are trabeculae in lymph nodes? What is located here?
CT septa that extend from into the lymph node carrying blood vessels and nerves?
What carries blood vessels and nerves into lymph nodes?
Trabeculae
What is the site where blood vessel and efferent lymphatic vessel leave the lymph node?
Hilum
What forms the inner part of the lymph node?
Cortex + Medulla
What are the vessels that bring in lymph/blood to the lymph node? What specialization do these have?
Afferent lymph vessels that have valves
What are the three sinuses of lymph nodes?
Subcapsular
Trabecular
Medullary
Where are subscapular sinuses located in lymph nodes? What do these sinuses drain into?
Just beneath the capsule, and drain into trabeculae
Where are the trabecular sinuses located, and where do they drain?
Found separating the lymphatic nodules from trabeculae, and drain into medullary sinuses
What two cells types are found within trabecular sinuses, and what are their function?
Endothelial cells which act as gates for lymph and reticular cells that serve as anchoring points for macrophages
All lymph sinuses are lined by what type of cells?
Macrophages
What is the last sinuses in lymph nodes that are found in the deepest layer, and are wide and tortuous?
Medullary sinuses
What do the medullary sinuses drain into?
Efferent lymph vessels
What is the framework that suspends cells in the lymph node made from? What cells make it?
Reticular fibers from reticulocytes
What is the flow of lymph through a lymph node?
- Afferent lymphatic vessels (numerous, penetrate capsule, have valves)
- Subcapsular (cortical) sinus (located between capsule and parenchyma)
- Trabecular sinuses
- Medullary sinuses – interconnected lymphatic channels (wide, tortuous)
- Efferent lymphatic vessels (at hilum, have valves)
What are the three types of cells that are found in the reticular tissue of lymph nodes?
Reticulocytes
Dendritic cells
Macrophages
Follicular dendritic cells
What is the function of reticulocytes?
Synthesize collagen III (reticular fibers)
What is the function of the dendritic cells in lymph tissue?
Anitgen presenting cells that monitor for foreign substances
What is the function of the macrophages found in lymphatic tissue?
Phagocytic
What is the function of the follicular dendritic cells of the reticular tissue?
Bind antigen complexes
What is the parenchyma part of lymphatic cells?
The cellular part
What are the three components of the parenchyma cells?
Cortex
Paracortex
Medulla
What is the function of the dendritic recticular cells that are a part of the cortex of lymph nodes?
bind newly synthesized immunoglobulin and when these cells re-encounter the same antigen, they bind it and present it to the B- and T-lymphocytes
What does the paracortex part of lymph nodes contain?
- T-lymphocytes
2.
Does the cortex part of lymph tissue have more or less cells than the medulla part?
More
What is the thymus-dependent part of the lymph node? Why?
The paracortex, because it receives B and T lymphocytes from the blood via high endothelial venules
What is the function of the high endothelial venules of lymph nodes?
Receive 90% of the B and T lymphocytes from the blood produced by the thymus
What are the two routes into lymph nodes that B and T lymphocytes may take?
Through afferent lymph vessel (10%)
High endothelial venules
What is contained in the Medullary cords of the medulla of lymph nodes?
Reticular cells/fibers
Lymphocytes
Plasma cells
(Most cells associated with lymph nodes)
Are lymphatic nodules primary or secondary? Permanent or temporary?
Secondary, thus permanent
What is the blood supply/flow of lymph nodes?
- Hilum
- trabeculae
- medulla
- medullary cords
- Form capillaries
- empty into post capillary venules
Where are B-lymphocytes primarily found in lymph nodes?
Cortex
Where are T-lymphocytes primarily found in lymph nodes?
Paracortex
Where do the t-lymphocytes that are present in lymph nodes ultimately come from?
Thymus
Where are the high endothelial venules found in the lymph node?
In the paracortex
What is the epithelium that lines high endothelial venules?
simple cuboidal to columnar
What happens to B and T lymphocytes when the leave the high endothelial venules?
B go to the cortex
T go the the paracortex
What are medullary cords?
Clumps of cells that contain plasma cells, dendritic cells, macrophages
Are the sinuses of lymph nodes empty spaces?
No–filled with reticular cells lymphocytes
Do the plasma cells leave the lymph node, or just their antibodies?
Just the antibodies
Where to T lymphocytes originate from? Where do they go to after that?
Bone marrow, go to thymus where they mature
How many lobes are they to the thymus?
2
What is the capsule of the thymus made of?
Dense, irregular collagenous CT
What partitions the thymus to form thymic lobules?
Trabeculae
What are the two compartments of each thymic lobule?
cortex and medulla
Are the lobules of the thymus completely separate?
No
What does the capsule of the thymus contain?
Blood vessels, efferent lymphatic vessels and nerves
What does the CT of the thymus contain?
Collagen, fibroblasts, plasma cells, granulocytes, lymphocytes
mast cells
adipose cells
Macrophages
True or false: the medulla of each thymic lobule is distinct and separate?
False–all are connected
What happens as t-lymphocytes migrate through the cortex to the medulla?
Mature
What is the framework for the thymus?
Epithelial retciular cells
What are type I reticular cells?
Cells that forma a seal around the cortex of the thymus, separating it from the CT capsule and trabeculae
What are the junctions between type I reticular cells?
Occludens (tight) junctions
What are type II epithelioreticular cells?
Are cells that branch in a stellate fashion to form a meshwork in the mid cortex
Functions as “teachers”
What are type II epithelioreticular cells connected by?
Desmosomes
What are type III epithelioreticular cells?
Cells that reside deep in the cortex of the thymus, and form the corticomedullary junction, forming a seal between the cortex and the medulla
What common function do all three types of epithelial reticular cells have?
Protection the thymus and isolate it from antigens
Which type of epithelioreticular cells form the blood-thymus barrier? What are the other components of this? (4)
- Type I cells
- Basal lamina
- Cortical capillary endothelium
- Macrophages
Where are the first four types of epithelioreticular cells found?
I = outer
II = in the cortex
III and IV = at the medullary and paracortex junction
What are type IV epithelial reticular cells? What do they do? Where are they found?
cells are associated with Type III cells and participate in the establishment of a “barrier” at the corticomedullary junction
What are type V epithelial reticular cells? What do they do? Where are they found?
form the meshwork / cytoreticulum (framework) of the medulla
What are type VI epithelial reticular cells? What do they do? Where are they found?
form thymic corpuscles called Hassall’s corpuscles - concentric, eosinophilic, whorls, unique to the thymic medulla. They exhibit keratinization
What are Hasall’s corpuscles? Do they stain darker or lighter than the surrounding tissue?
Areas formed by type VI epithelioreticular cells that contain mature T-lymphocytes
Stain lighter
Where do immuocompetent T lymphocytes leave the thymus? Where do they go?
Via postcapillary venules to go to the paracortex of lymph nodes, PALS of the spleen, GALT, and BALT
Where is the only place that Hasall’s corpusles are found?
Thymus
What is DiGeorge’s syndrome?
Developmental disorder where the thymus does not develop, thus causing an inability to produce T lymphocytes.
Death = by infection
Where is the major site of T and B lymphocytes proliferation?
Spleen
What is the white pulp of the spleen made of?
PALS
Splenic nodules
What suspends the red pulp?
Reticular fibers
What are the two major components of the spleen?
Red and white pulp
What is contained in the Red pulp of the spleen?
Splenic sinuses
Spelnic cords
What is the function of splenic sinuses? What are they lined by
Are lined by endothelial cells, with wide intercellular spaces allowing blood cells to pass in and out of the sinuses
Drain into pulp veins which in turn drain into trabecular veins
What is the artery that enters the spleen at its hilum? What does it give rise to once inside?
Splenic artery, which gives rise to trabecular arteries
What happens to the trabecular arteries once they enter they leave the CT of the trabeculae?
Loose their tunica adventitia, and are infiltrated with T-lymphocytes
What is the periarteral sheath?
T-lymphocyte covered central artery in the spleen
What are the arteries that lose their T-lymphocyte sheath and penetrate into the red pulp?
Penicullar arterioles, then arterial capillaries
Where do the arterial capillaries and sheathed capillaries in the spleen drain into?
Splenic sinuses
What is the path of blood flow in the spleen? (7)
- Spenic artery
- Trabecular arteries
- PALS, central artery
- Penicillar arteries
- Arteriole capillaries
- Sheathed capillaries
- Splenic sinuses
What color does white pulp in the spleen stain?
Basophilic Blue
What is the part of the spleen that contains T-lymphocytes?
White pulp
What are splenic nodules? What do they contain? Where are they found
Lymphatic nodules in the white pulp that contain B lymphocytes
What is the marginal zone of the spleen?
Between the red and white pulp
What are the two components of the red pulp? What does it stain with?
- Spelcni cords
- Splenic sinuses
Eosinophilic
What are the splenic cords that make up the red pulp of the spleen?
They are irregular branchig cords of tissue consisting of reticular fibers/cells, with the spaces between fibers filled with filtered blood
What are the splenic sinus of the red pulp in the spleen? What are their function?
Sinuses lined by enothelial cells.
Drain blood into pulp veins, which drain into trabecular veins
