Lymphatic system Flashcards
What are the primary lymphatic tissues?
Bone marrow
Thymus
What are the secondary or peripheral lymphatic tissues?
Spleen
LN
-Mucosa associated lymphatic tissue or nodular non-encapsulated lymphatic tissues
What are the components of lymphoid tissues?
Stroma
Lymphoid cells
What is the stroma of the lymphatic tissues made up of?
Cells and reticular fibers
- Reticular cells (fibroblasts)
- Macs
- DC
- FDC
How would you diff lymph nodes from nodules?
smaller
- no capsule
- nodules have no filter because no connection with lymphatic vessel
- its still a localized production of lymphoctyes
What does a 1’ lymphatic nodule look like and how would one tell it apart from a 2’?
- dark staining spherical balls
- where 2’ contain a reaction germinal center
what are some other features of 2’ lymphatic nodules?
- Appear after birth
- antigen dependent
- thymus required for dev
- numerous in childhood then decline
Where can nodules appear?
spleen
solitary
LN
-NOT THE THYMUS
What are some examples of non-encapsulated nodular lymphatic tissues?
Tonsil
- Palatine, lingual, tubal and pharngeal
Peyer’s patches
Appendix
What are some functions of non-encapsulated lymphatic tissues?
Trapping antigen
- destruction of antigen
- selection of memory lymphocytes
- B-Cell proliferation
What are the encapsulated lymphatic tissues?
LN
Spleen
Thymus
What are some unique qualities of lymph nodes?
only organ located in course of lymphatic vessels
- only 1 with lymphatic sinuses
- only 1 that filters lymph
What is responsible for the filtering of lymph?
Macs
What are some morphological features of LN?
Capsules
Trabeculae
Stroma
Endothelial cells
What are the 2 division of the LN?
Cortex and Medulla
What are the subdivisions of the cortex of LN’s?
Superficial
Mid
Deep (paracotex)
What is the thymus dependent zone found?
Deep cortex
how do lymphocytes leave the LN?
Via efferent lymphatics at hilus (called recirculating lymphocytes then)
What is the flow of lymph?
Afferent Lymphatic vessels
- subcapsular sinus
- trabecular sinus
- paracortical sinus
- medullary sinus
- efferent lympmhatic vessel
What is HEV?
High endothelial venule
- thickened endothelium that only lymphocytes can cross
- then these lymphocytes can recirculate
What is the blood flow through LN’s?
Arterial vessels (Hilus)
- trabecular vessels
- arterioles and capillaries
- post capillary venules
- venous vessels (hilus)
What is the purpose of thymic hormones on HEV?
Needed for maintenance and formation of HEV
Where can lymphocytes divide that RBC’s and granulocytes cannot?
Nodules
What are the function of the lymph node?
Filers lymph via macs
lymphocyte production
antibody production (plasma cells)
When is the thymus largest proportionally?
in the first 2 year of life
- increase in size till puberty and less after that
What is the development of the thymus?
Endoderm via 3rd brachial pouch
Where is the thymus located?
Beneath sternum on upper ant thoracic wall
- anteriosuperior mediastinum
where would you find Hassall’s corpuscles and what do they look like?
Medulla of thymus
- Keratinized
What are the major suppliers of the thymus in terms of arterial supply?
Internal thoracic and inferior thyroid
What is the purpose of the blood- thymus barrier and how is it kept?
Prevents antigens in blood stream from entering the thymic cortex
- Endothelial cell tight junctions
- basal lamina of endothelial cells
- perivascular (CT) space
- epithelial reticular cells with desmosomes
What is the spleen?
largest lymphatic organ
- no afferent lymphatic vessels
- efferent lymphatic vessles present
- no lymph sinuses
- filters blood and lymph
What can take over function of spleen if lost?
BM and liver
Does the spleen have a medulla or cortex?
No
- capsuled by smooth muscle
- thick ct trabeculae
- splenic pulp white and red
- hilus
What is splenic pulp?
Consists of blood cells embedded in and supported by reticular fiber stromal network
- 2 types (red & white)
What are the compartments of white pulp?
Periarterial lymphatic sheaths (PALs)
- Splenic (lymphatic) nodules
Where are T cells mainly contained in the pulp?
PALs
- splenic contains primarily B-cells (scattered throughout)
What the the subdivisions of the red pulp?
- Splenic sinuses (sinusoids)
- Splenic cords (billroth cord)
- Marginal Zone
What are the splenic sinuses?
Vascular passageways
lined by specialized enothelial cells
What are splenic cords?
Located between the sinuses
- contain RBC’s, granulocytes, lymphocytes. macs, platelets, plasma cells, reticular cells and fibers
What is the marginal zone?
transitional zone between red and while pulp
- small blood vessels dump their blood into this area
-
Where do closed circulation terminate?
Open into sinusoids
Where doe open circulation of the spleen terminate?
open into red pulp
What are sinusoids?
Consist of elongated and narrow endothelial cells
- supported by basement membrane and reticular fibers that encircle the sinusoid
WHat are the splenic immune functions?
APC
- activation and prolif of B and T cells
- production of antibodies against antigen in blood
- removal of macromolecular antigens from blood
What are the spleens hemopoietic functions?
remove and destruct abnormal RBC’s and platelets
- retrieval of iron from hemoglobin
- formation of RBC’s and granulocytes during fetal life
- store blood (RBC’s and platelets)
