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What is lymphoid tissue
It is a type of connective tissue characterized by its rich supply of lymphocytes
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What is the support system in lymphoid tissue
Reticular fibrils
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What are the reticular fibers made from
Fibroblasts called reticular cells
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Reticular cells, and therefore fibroblasts are derived from what embryonic tissue
Mesoderm
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The epithelial cells are derived from what embryonic tissue
Endoderm
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When lymphoid tissue is encapsulated by connective tissue it is called
A lymphoid organ (Lympth nodes)
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What is a lymphoid nodule
A bundle of lymphoid cells found in connective tissue
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What is the importance of Mucosa-associated lymphoid tissue (MALT), and where can it be found
It forms a protective barrier (GI, respiratory, reproductive, urinary)
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What is the main distinction between primary and secondary lymphoid nodules
Secondary lymphoid nodules have activated B cells
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Primary lymphoid nodules are absent of
Plasma cells and a germinal center
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Primary lymphoid nodules contain
B Lymphocytes both naive, and B memory cells
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Secondary lymphoid nodules contain what cells that primary nodules lack
- APC's
- Activated B cells
- Germinal centers
- Plasma Cells
- Follicular Dendritic cells
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How is the germinal center formed in the secondary nodules
APC's activate the B cells and they proliferate forming the germinal center
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Follicular dendritic cells differ from traditional dendritic cells in that
They do not act as antigen presenting cells because they do not contain Class II markers
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Follicular Dendritic cells perform what role
They help activate B cells
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MALT contains a lot of what cells
- B cells
- Helper T cells
- Macrophages
- Plasma cells
- APC's
- Lymphoid nodules
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What is a Peyers patch
This is a aggregation of lymphoid nodules in the Ileum
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What are the primary lymphoid organs and why
Thymus and bone marrow, these are the locations that the B and T cells become immunocompetent
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What are the secondary lymphoid organs and why
- Spleen
- Lymph nodes
- Tonsils....
- This is where the immunocompetent cells migrate for action
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Palatine tonsils are located where and have what features
- They are located in the roof of the mouth on the two sides just before the esophagus.
- They are incompletely encapsulated by stratified squamous non-keratinized epithelium containing 10-20 crypts
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Ligual tonsils are located where
Dorsal surface of the posterior 1/3 of the tongue, and have a single crypt
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Thymus is made up of what cells
- T cells
- macrophages
- epithelial cells
- reticular cells
- No B cells
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Hassells corpuscles are found only in
The medulla of the thymus, function is unknown
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The thymus has what two primary zones in its lobules
Medulla and Cortex
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The medulla of the thymus contains what cells
- T cells
- Epithelial reticular cells
- Macrophages
- Hassall corpuscles
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What is unique about the capillaries in the thymus
They are non-fenestrated (no openings), and have a thick basal lamina making them impermeable to proteins and circulating antigens
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Which part of the thymus contains the T cell precursors
The cortex
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When does the thymus reach its greatest size
At puberty, then it shrinks
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What is an additional cell found in the thymus to help with its function in the immune system
Nurse cells that assist T cells in their development
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What happens to T cells in the thymus cortex
They divide by mitosis, presented to self antigens bound to class I and II MHC molecules.
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What is unique about the T cells precursor cells in the thymus
Only 5% of them survive and migrate to the medulla
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What happens to T cells in the medulla of the Thymus
They mature and then are distributed to the rest of the body
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What are the four hormones in the epithelial cells of the thymus that are required for proper T cell maturation
- Thymosin
- Thymopoietin
- Thymulin
- Thymic humoral factor
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What is DiGeorges syndrome
- Congenital Thymic aplasia
- There is abnormal cell mediated immunity, but normal humoral immunity
- Patients have a unique facial structure
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What is the function of the lymph nodes
They are filters of the circulatory system
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What are the primary layers of a lymph node and their contents
- Capsule
- Subcapsular sinus
- Superficial cortex - B cells
- Paracortex - T cells
- Medulla - Plasma cells
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All of the lymph in tissue must pass through
At least one lymph node before entering the blood stream
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What portion of the lymph nodes has high endothelial vessels
The inner or paracortex
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In the lymph nodes the B cells and T cells go to what differing areas
- B cells to the cortex
- T cells to the paracortex
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The high endothelial vessels in the paracortex of the lymph nodes are lined by what cells
Simple cuboidal cells
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What is the route of blood in the lymph nodes
Artery - Hilum of node - cortical capillaries surrounding lymph nodules - high endothelial vessels (Post capillary venules)
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What is Hodgkin Disease
Painless progressive enlargement of lymph nodes, liver, spleen, fever, anemia, and weight lose
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What is the largest lymphoid organ
Spleen
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What is the primary job of the spleen
- To filter the blood and remove worn out RBC's, phagocytes, as well as mount immune responses.
- It is also a production site of activated lymphocytes
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What are the two major components of the pulp on the spleen
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What does the white pulp contain
PALS (periarterial lymphatic sheath) made of T cells, and lymphoid nudules
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When the splenic artery enters the spleen what is the path it undergoes
- Trabecular arteries
- Central artery (encapsulated by PALS)
- Pass the marginal zone
- Enter red pulp
- Leave Trabecular vein
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What is the purpose of the marginal zone in the Spleen
Plays an important role in immunological activities in that it contains many blood antigens
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What does the germinal center of lymphoid nodules contain a lot of
B Cells
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What are the two main components of the red pulp of the spleen
- Splenic cords (Dense lymphoid tissue)
- Sinusoids (irregular blood vessels)
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Splenic sinuses have what important feature for movement of blood
Lots of openings
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What is the difference between a closed system and an open system
The blood in a closed system always remains in the vessels, in an open system the blood opens to the splenic cords and passes through the cells to reach the sinusoids
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Class switching of immunoglobulins primarily happens where
Germinal center of lymphatic nodules
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Dendritic cells are only found where in the lymph nodes
Outer cortex
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Cytotoxic T cells kill target cells via
Lysing them with perforins and fragmentins
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Immunocompetent T cells migrate where in the thymus
To the pariarterial lymphatic sheath
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