Lymphoid Tisssue Flashcards
1
Q
Lymphoid Tissue
A
Specialized connective tissue that protects against infection
2
Q
Primary Lymphoid Tissue
A
- Sites where lymphocytes are produced or mature
- Includes the bone marrow and thymus
3
Q
Secondary Lymphoid Tissue
A
- Sites where lymphocytes interact and begin immune responses
- Includes lymph nodes, tonsils, spleen, and diffuse lymphoid tissue
4
Q
Lymphatic Nodules/Follicles
A
Key histologic characteristic of most lymphoid tissue
-
Primary Follicle (blue circle in picture)
- Lacks germinal center
-
Secondary Follicle (orange circle in picture)
- Inner pale area is the germinal center of proliferation B-cells which are activated and develop into plasma/memory cells
- Outer darker area is the corona/mantle made of mature cells
Infection increases the number of secondary follicles
5
Q
Lymphatic Vessels/Ducts
A
- Collects proteins, lipids, immune cells, and interstitial fluid from tissue, which is then filtered through lymph nodes, and returned to vascular system
- Single layer of endothelium that lacks continuous basal lamina, thus has leaky vessels in loose connective tissue
- Valves prevent backflow; body movement moves contents
- Thoracic duct and right lymphatic trunk drain into venous system
6
Q
Lymph Nodes
A
- Bean shaped lymphoid organ
- Filters lymph for pathogens
- Lymph enters through afferent vessels on convex surface
- Lymph leaves through efferent vessels on cacave surface
7
Q
Lymph Node Cortex
A
- Outer portion of the lymph node
- Contains follicles, macrophages, reticular cells, and follicular dentritic cells (resident cells in the follicles)
8
Q
Lymph Node Paracortex
A
- A layer deeper than the cortex
- Contains T-Cells and high endothelial venules (HEVs)
- HEVs are specialized blood vessels that bring circulation lymphaocytes into the lymph node
9
Q
Lymph Node Medulla
A
- Layer deeper than both the cortex and paracortex
- Contains medullary sinusoids and medullary cords
10
Q
Lymph Node Capsule
A
- Outermost part of the lymph node
- Made from dense connective tissue covering
- Includes trabeculae which are infoldings of the capsule
11
Q
Lymph Node Subcapsular Sinus
A
- Entry point for afferent lymph vessels
- Lots of macrophages (blue arrows in picture) and dentritic cells
- Reticular cells make collagen III scaffolding
12
Q
Lymph Node Medullary Sinusoids
A
- In the Medulla of the lymph node
- White spaces between cells (blue arrows in picture)
- Lined by endothelium and merge into efferent lymph vessels
13
Q
Lymph Node Medullary Cords
A
- In the medulla of the lymph node
- Group of cells surrounding the sinusoids (orange arrow heads in the picture)
- Contains plasma cells and lymphocytes
14
Q
What are the two ways for cells to enter the lymph nodes?
A
- HEV: niave T and B cells often enter this way
- Afferent lymphatic vessels: dendritic cells commonly enter this way
15
Q
Types of Diffuse Lymphatic Tissue
A
Mucosal Associated Lymphatic Tissue (MALT) with the following subcategories:
- Bronchus/Nasal Associated Lymphatic Tissue (BALT/NALT)
- Gut Associated Lymphatic Tissue (GALT)
16
Q
Mucosal Associated Lymphatic Tissue (MALT)
A
- Non-encapsulated aggregation of lymphocytes beneath epithelia (lamina propria) of GI, respiratory, and GU tissue
- Subcategories include BALT/NALT and GALT
17
Q
Bronchus/Nasal Associated Lymphatic Tissue (BALT/NALT)
A
- Lymphoid aggregation in respiratory tract
18
Q
Gut Associated Lymphatic Tissue (GALT)
A
- Lymphoid aggregations in the GI tract (orange outline in picture)
- Vermiform appendix (will be shown in Block 5)
- Peyer’s Patch: mergers of lymphatic tissue in the ileum of the small intestines (blue arrows in picture)
19
Q
Tonsils
A
- Lymhoid tissue in the throat
- Combats antigen of nose and mouth
- Have lymphatic follicles (blue arrows in picture)
- Tonsils are covered in epithelia (stratified squamous or pseudostratified)
- Crypts are invaginations of the surface epithelia (yellow arrowhead in picture)
20
Q
Thymus (location, function, and development)
A
- Bilobed organ located anterior to the heart
- Site of T-cell maturation
- Develops from endoderm and mesoderm
21
Q
Thymus Structure
A
- Trabeculae (arrows in picture) section thymus into thymic lobules (bracket in picture)
- Immature T-cells in the cortex. Mature as they move toward the medulla. Mature naive T-cells exit via blood or lymph vessels.
- No lymphatic follicles
22
Q
Thymus Hassall’s Corpuscles
A
- Worls of eosinophilic cells of unkown function
- In the medulla of the thymus
- Key histology feature helpful for identifying the thymus
23
Q
Spleen
A
- Largest lymphoid organ in the body
- Locted in the upper left quadrant of abdominal cavity
-
White Pulps (blue arrows in picture)
- Made of lymphatic nodules (dark circles in picture)
-
Red Pulp (yellow arrowheads in picture)
- Red due to large population of RBCs
- Macrophages in red pulp filder damaged RBCs and sample antigens
- Contains splenic cords formed by reticular cells and houses many cells types
24
Q
Periarteriolar Lymphoid Sheath (PALS)
A
- Part of the white pulp of the spleen
- Acts similar to lymph nodes but the spleen is better at catching blood-borne pathogen antigen
- T and B cells can be activated and differentiate here
- T-cell zone is in the interior; B-cell zone is in the exterior
25
Q
Spleen Central Artery
A
- Surrounded by PALS (mostly T-cells and some marcophages)
- Found in the center or edge of lymphatic follicles
26
Q
Red Pulp Histology
A
- Splenic sinusoids (blue arrows in picture): lighter area surrounded by macrophages
- Splenic cords (yellow arrowhead in picture): loose connective tissue and cells between sinusoids filled with multiple immune cells
27
Q
Lymphoid Tissue Flow Chart
A
