Lymphatic system Flashcards by Keaton Joppru

What are the primary lymphatic tissues?

Bone marrow

Thymus

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What are the secondary or peripheral lymphatic tissues?

Spleen
LN
-Mucosa associated lymphatic tissue or nodular non-encapsulated lymphatic tissues

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What are the components of lymphoid tissues?

Stroma

Lymphoid cells

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What is the stroma of the lymphatic tissues made up of?

Cells and reticular fibers

Reticular cells (fibroblasts)
Macs
DC
FDC

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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

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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

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what are some other features of 2’ lymphatic nodules?

Appear after birth
antigen dependent
thymus required for dev
numerous in childhood then decline

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Where can nodules appear?

spleen
solitary
LN
-NOT THE THYMUS

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What are some examples of non-encapsulated nodular lymphatic tissues?

Tonsil
- Palatine, lingual, tubal and pharngeal
Peyer’s patches
Appendix

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What are some functions of non-encapsulated lymphatic tissues?

Trapping antigen

destruction of antigen
selection of memory lymphocytes
B-Cell proliferation

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What are the encapsulated lymphatic tissues?

LN
Spleen
Thymus

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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

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What is responsible for the filtering of lymph?

Macs

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What are some morphological features of LN?

Capsules
Trabeculae
Stroma
Endothelial cells

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What are the 2 division of the LN?

Cortex and Medulla

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What are the subdivisions of the cortex of LN’s?

Superficial
Mid
Deep (paracotex)

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What is the thymus dependent zone found?

Deep cortex

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how do lymphocytes leave the LN?

Via efferent lymphatics at hilus (called recirculating lymphocytes then)

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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)