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83 Cards in this Set
- Front
- Back
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What is the major cellular component of the immune system?
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Lymphocytes
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2 main types of immune system organs:
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-Primary lymphatic organs
-Secondary lymphatic organs |
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What are lymphocytes a type of?
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WBC
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T lymphs mature in____
B lymphs mature in ____ |
T in Thymus
B in Bone marrow |
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Where are clusters of lymphocytes found?
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In lymph nodes, tonsils, and spleen.
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Where are smaller aggregates of lymphocytes found?
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In MALT
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Are lymphocytes part of innate or adaptive immunity?
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Adaptive
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What are Bcells responsible for?
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Humoral immunity
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What are Tcells responsible for?
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Cell mediated immunity
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What is the characteristic microstructure of a plasma cell?
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-Clock faced heterochromatin
-Eccentric nucleus -Extensive rER -Perinuclear golgi apparatus |
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What does the structure of a plasma cell indicate about its function?
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It is a very active cell that is intensely making and secreting protein for export (Antibody)!
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What are the 5 Ig types made by Bcells?
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GAMED
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What is the thymus surrounded by?
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Loose connective tissue CAPSULE
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What does the capsule do?
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Extends into the thymus as SEPTAE
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What do the capsular septae divide the thymus into?
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Lobules
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What lies within the septae of the thymus?
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-Blood vessels
-Nerves -Efferent lymphatic vessels (?) |
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What differentiates the cortex and medulla of the thymus?
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Cortex = basophilic
Medulla = paler |
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Why are the medullary portions of adjacent lobules continuous?
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Because septae only penetrate the thymus to the cortico-medullary junction.
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Where in the thymus are thymocytes more concentrated?
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In the cortex
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What happens to immature thymocytes if they survive positive selection in the cortex?
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They migrate to the medulla to undergo negative selection
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What happens to Tcells that survive negative selection in the medulla?
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They enter efferent lymphatic vessels and go to 2ndary lymphatic organs or other tissues.
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What cells are in the thymus other than lymphs?
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Epithelial cells
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What links epithelial cells to form a supportive scaffolding for thymocytes?
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Dendritic processes, connected by Desmosomes
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How is the supportive scaffold in the thymus unique from other lymphatic organs?
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Most lymphatic organs have a scaffold of reticular fibers
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What happens to thymocytes whose receptors bind weakly with peptide/mhc complexes presented by epithelial cells?
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They die via PCD.
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What percent of thymocytes survive positive selection?
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2%
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What are the onion shaped aggregates of eosinophilic epithelial cells in the medulla of the thymus?
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Hassall's corpuscles
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What do Hassall's corpuscles do?
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Catabolize apoptotic thymocytes
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What is the function of the Blood-thymus barrier?
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To ensure that Tcells do not come in contact with foreign antigens during the process of negative selection.
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What happens in secondary lymphatic organs?
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Mounting of an immune response using the competent lymphocytes from the primary organs.
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What are secondary lymphatic organs like?
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Flimsy meshlike filter bags
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What is the mesh? What is it made of it it's lymph nodes? What if it's spleen?
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Stroma
-made of reticular fibers in lymph nodes -made of combined smooth muscle and reticular fibers in spleen |
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What are the 'filter' components in lymph nodes?
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-Tcells
-Bcells -Macrophages |
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How are T/Bcells and Macrophages arranged in lymph nodes?
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-Bcells are peripheral/cortical
-Tcells and macrophages in medulla |
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What is the filter component of the spleen?
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White pulp
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What does white pulp consist of?
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-Follicles of Bcells
-PALS of Tcells |
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What is red pulp in the spleen?
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Where RBCs are degraded
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What are the small, blindended capillary-like structures that drain ECF from almost all tissue spaces?
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Lymphatic capillaries
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What happens to the lymph fluid in the lymphatic system before it is returned to the circulation via the thoracic duct?
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It gets FILTERED by our meshlike filter bags - lymph nodes - to remove foreign antigens that may be floating in the ECF.
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What makes up the stroma of the lymph node, and what is it for?
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-Reticular fibers
-Fibroblasts It slows the flow of lymph so it comes in good contact with lymphocytes and macrophages. |
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what surrounds lymph nodes?
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A connective tissue capsule
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What is the little space underneath the capsule?
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Subcapsular sinus
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What are the circular clusters in the cortex that are uniform in intesnsity? What do they consist of?
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Primary lymphoid follicles - naieve Bcells that are quiescent.
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What are the 2 visible features of a secondary lymphoid follicle?
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-Mantle zone
-Light germinal center |
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What could be visible within the germinal center?
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Mitotic figures
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What happens as activated Bcells from germinal centers migrate to the medulla?
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They form cellular tissues called Medullary cords separated by lymph-filled sinuses.
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What do Bcells do when they get to the medulla of the lymph node?
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Release their antibodies to the antigen they had reacted to to go into the general circulation.
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What area lies between the cortex and medulla of the lymph node?
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Paracortex
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What cell dominates the paracortex?
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T cells
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What other important structure is in the paracortex?
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High endothelial venules
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Why do lymph nodes ABSOLUTELY NEED high endothelial venules?
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Because that's where lymphocytes from the blood enter the nodes via homing receptors.
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What does a germinal center in a lymph follicle indicate?
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That new B cells are being produced in response to an antigenic stimulus
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What does a high endothelial venule do?
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Serves as the conduit by which lymphocytes enter and are sequestered in lymph nodes.
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When you palpate a patient's "swollen glands" what are you really palpating?
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lymph nodes that are enlarged and have triggered a pain response.
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What does the carbon stain show in a lymph node?
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The reticular stroma
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What cells sequester carbon?
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Macrophages
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Where the lymph nodes filter foreign antigens from lymph, what does the spleen do?
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Filters them from blood
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On an H/E slide of spleen, what color is red pulp? White pulp?
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Red = red - RBCs
White = blue - WBCs |
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What does red pulp consist of?
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Blood-filled sinusoids
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What separates these sinusoids?
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Cords of densely packed lymphocytes which are White pulp
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What is the approx age of RBC?
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120 days
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When small branches of the splenic artery enter the substance of the spleen, what are they surrounded by?
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Periarterial lymphatic sheath
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What type of cell is in PALS?
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Tcells
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What is within PALS?
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Lymphoid follicles of Bcells
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What are the vessels that are surrounded by PALS?
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Central arterioles
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What do the arterioles and surround PALS together make up?
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White pulp
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What fibers are abundant in the splenic capsule, trabeculae, and blood vessel tunics?
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Reticular fibers
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What are 3 solid organs that have a stroma composed of reticular fibers?
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-Spleen
-Lymph nodes -Liver |
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What do we remember makes up the stroma of the thymus?
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Epithelial cells
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What type of epithelium covers the surface of the palatine tonsil?
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Stratified squamous
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What are the tonsils an example of?
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Isolated lymphatic tissue
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How are the palatine tonsils organized?
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Into crypts, with follicles that are lined up along them.
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What do we call the structure of the palatine tonsils?
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Organized follicles
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What is the function of the lymphatic tissue that encircles the entrance to the GI tract?
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To protect the GI tract by reducing the number of foreign pathogens entering it.
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In what other areas of the body would you find isolated lymphatic tissue organized as lymphatic follicles?
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-Gastrointestinal tracts
-Urinary tracts -Respiratory tracts -Reproductive tracts |
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Where isolated lymphatic tissue forms organized follicles in the tonsils, what does it ALSO form in the ileum?
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Diffuse lymph aggregates
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Looking at the ileum, what are intensely basophilic structures just under the GI tract epithelium?
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ORGANIZED lymph follicles
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What is in the lamina propria of the epithelium?
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DIFFUSE lymph aggregates
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What cells make up diffuse lymph aggregates?
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-Lymphocytes
-Plasma cells -Eosinophils |
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What is the acronym for lymphatic tissue in the GI tract?
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GALT
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Plasma cells are the differentiated product of what cell type?
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B cells
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If plasma cells are intensely secreting antibody, why don't they have more heterochromatin?
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Because it's all the same type of antibody - don't need all their genes active.
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What are large collections of lymph follicles in the ileum called?
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Peyer's patches
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