Lymphatic Organs & Tissue Flashcards
Lymph nodes
Small bean shaped encapsulated lymphatic organs located along the pathway of lymphatic vessels
2 types of lymphatic vessels
Afferent & efferent lymphatic vessels
Afferent lymphatic vessels
Bring lymph into lymph node
Efferent lymphatic vessels
Brings lymph away from lymph node at the hilum
Hilum
Concave depression on the concave surface, serves as an entrance/exit for blood & lymphatic vessels & nerves
Supporting elements of lymph nodes
Capsule
Trabeculae (CT septa)
Reticular tissue
lymph nodes
Capsule is composed of…
dense irregular CT
lymph nodes
Trabeculae (CT septa)
CT extensions from the capsule that extend into the lymph node forming a supportive framework
lymph nodes
Reticular tissue
Reticular cells & fibers form a fine supporting meshwork
General architecture of lymph node
Parenchyma divided into cortex & medulla
lymph nodes
Parenchyma is divided into ____ and ____
Cortex & medulla
lymph nodes
Subcapsular sinus
Immediately below the capsule, receives lymph from afferent lymphatics
lymph nodes
Cortical (trabecular) sinuses
Branching from the subcapsular sinus among the lymphatic nodules within Trabeculae
Lymphatic (lymphoid) nodules
Round aggregations of lymphocytes, mostly B lymphocytes (B cells)
2 types of lymphatic nodules
Primary & secondary lymphatic nodules
Primary lymphatic nodule immune function
Currently no immune response
Secondary lymphatic nodule immune function
Immune response to antigen presentation
Secondary lymphatic nodules structure
- paler germinal centre of proliferating lymphocytes (mostly B cells) surrounded by corona (mantle) of smaller mature B lymphocytes
Lymphatic nodules may transition into ____
Diffuse lymphatic tissue - random lymphocyte arrangement between nodules
(Not bound by CT)
lymph nodes
Paracortex
Deeper extension of the cortex, no lymphatic nodules, diffuse lymphatic tissue, mostly T cells
lymph nodes
High endothelial venules (HEVs) are located in the ____
Paracortex
lymph nodes
Paracortex contains mostly ____
T cells
High endothelial venules (HEVs)
Specialized post capillary venules, entry point for most circulating lymphocytes
lymph nodes
2 major components of medulla
Medullary cords
Medullary sinuses
lymph nodes
Medullary cords
Branched, cord-like masses of reticular fibers containing mostly B lymphocytes, and plasma cells. T lymphocytes, macrophages and dendritic cells
lymph nodes
Medullary cords contain branched cord-like masses of ____
Reticular fibers
lymph nodes
Medullary cords contains mostly ____
B lymphocytes
lymph nodes
Medullary sinuses
- Dilated lymphatic vessels with discontinuous endothelium, extending from cortical sinuses
- converge & empty into into efferent lymphatic vessel at the hilum
lymph nodes
Medullary sinuses extend from the ____
Cortical sinuses
Medullary sinuses converge & empty into the ____ at the ____
Efferent lymphatic vessel at the hilum
Thymus location
Bi-lobed organ in the superior mediastinum, anterior to the heart
Thymus function
Site of T-cell differentiation (into thymocytes) & proliferation
Only ____ reside in the thymus
T lymphocytes
General architecture of thymus
- CT capsule surrounding thymus
- Trabeculae (CT septa) extending from capsule into parenchyma, separating tissue into completely separate thymic lobules
Epithelioreticular cells
Features of reticular cells & epithelial cells
- supportive cells, no true CT fibers within a thymic lobule
Epithelioreticular cells function
- line capsule, Trabeculae & surround microvasculature, forming blood-thymus barrier
- form cytoreticulum to support thymocytes
Blood-thymus barrier
Prevents exposure of thymocytes (T cells) to antigens
thymus
Cortex
Each lobule has an outer darker staining region, more densely packed thymocytes (T cells)
thymus
Medulla
Paler staining (fewer thymocytes), Epithelioreticular cells more visible
thymus
Hassall’s corpuscles (thymic corpuscles) are located in the ____
Medulla
Hassall’s corpuscles
- Larger aggregates of concentrically wrapped Epithelioreticular cells, contain keratohyalin granules
- thought to produce factors (interleukins) that promote T cell development
Hassall’s corpuscles are thought to produce ____
Factors (interleukins) that promote T cells development
What are the specialized post Capillary venules located in the Paracortex of a lymph node, that act as an entry point for most circulating lymphocytes?
HEVs
Functions of spleen
- filter blood & react immunologically to blood-borne antigens (white pulp & red pulp)
- main site of destruction & removal of old, damaged & abnormal RBCs & platelets AND storage of extra RBCs (red pulp)
spleen
General architecture
CT capsule - surrounds spleen
Trabeculae (CT septa) - contain myofibroblasts
Hilum - splenic artery enters here
spleen
Functions of Trabeculae (CT septa)
- support trabecular arteries
- myofibroblasts help release RBC storage pool when necessary
spleen
Where does the splenic artery enter?
Hilum
spleen
Parenchyma consists of ____ & ____
Red pulp & white pulp
spleen
What is White pulp
Lymphatic nodules (primary or secondary, mainly B lymphocytes)
White pulp contains a ____
Central artery
spleen
What Branches from trabecular arteries?
Central artery
- splenic a.
- trabecular aa.
- central aa.
- penicillar arterioles
- sinusoids
spleen
Periarterial lymphatic sheath (PALS)
- Cylindrical aggregation of lymphocytes around the central artery
- mainly T lymphocytes in initial formation of white pulp
spleen
Red pulp is made up of…
Splenic cords (billroth cords)
Splenic sinusoids (sinuses)
spleen
Splenic cords (billroth cords)
Reticular tissue containing large numbers of stored RBCs, macrophages & lymphocytes, and plasma cells & dendritic cells
spleen
Splenic sinusoids (sinuses)
Sinusoidal capillaries, site where senescent RBCs are removed
spleen
Penicillar arterioles:
1/2 are ____
1/2 are ____
- 1/2 open ended: dumping blood into stroma of splenic cords
- 1/2 are typical closed circulation
Diffuse & Mucosa-Associated Lymphatic Tissue includes…
- MALT - mucosa associated lymphatic tissue (eg. GALT, BALT)
- tonsils
- Peyer’s patches (ileum)
- appendix
3 tonsils
- palatine tonsils
- pharyngeal tonsils (adenoids)
- lingual tonsils
What are tonsils?
- 3 irregular masses of lymphoid tissue in the oral cavity & nasopharynx
- cells encounter antigens entering mouth & nose
Immune cells in the tonsils are…
Not permanent
- lymphocytes come and go as necessary to accommodate immune response
Lymphocytes in appendix
Lymphocytes dispersed diffusely throughout CT of mucosa or aggregated into nodules
Immune cells of appendix are…
Not permanent
- lymphocytes come & go as necessary to accommodate immune response
