DD Thymus and peripheral lymphoid organs Flashcards Preview

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Flashcards in DD Thymus and peripheral lymphoid organs Deck (18)
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Why do blood vessels bypass the cortex via trabeculae?
Where do they enter?

Enter the medulla

ensures that differentiating T-lymphocytes (in cortex and medulla) do not get exposed to antigens in the blood until they are fully differentiated


What is the hallmark of the thymus? What is it?

Hassalls corpuscles
-circular light bodies in the medulla


2 arteries that enter the thymus?

Internal thoracid
inferior thyroid


Are there afferent and efferent supply of lymph to the thymus?

No afferent, just efferent


Describe the blood and lymphatic drainage of the thymus

Arteries in,
Venous and efferent lymphatic drainage out.


What creates the difference between the medulla and cortex of the thymus?

difference in lymphocyte population and staining of their nuclei

- lighter
- has hassals corpuscles (circular bodies)
- less lymphocytes

- darker
- characterized by its heavy lymphocyte concentration, is the site of much lymphocytic proliferation.


Describe lymphatic drainage entering the lymph node

Lymph enters lymph node via afferent lymphatic vessels along outer capsule > drains to subcapsulary sinus > reaches cortex + medulla via trabecular sinus > exit via efferent lymphatic vessel


Which vessels leave the lymph node? Thymus?

lymph node?
- efferent vessel
- artery
- vein

- efferent vessel
- vein


What is found in the germinal center and marginal zone of lymph nodes? explain the differences

GC: aggregation of lymphocyte in outer cortex of the lymph node
-rapidly dividing lymphocytes - stain lighter
-activated by B cells

MZ: lymphocytes
-stain darker


Do unchallenged lymph nodes contain germinal centers?


- challenged nodes/secondary follicles have clearly visible germinal center with a marginal zone surrounding it

- unchallenged /primary follicles have no germinal center


Whats special about high endothelial venules in paracortical region?

HEV are lined by thicker than usual endothelial cells > lymphocytes recognize and pass btwn

- allows circulating T and B lymphocytes to enter lymphatic fluid from blood

-HEVs are found in all secondary lymphoid organs (with the exception of spleen)


Which organ contains an abundance of plasma cells? Why is this important?

Spleen - many circulated Antibodies are produced here


Red pulp

RBC rich
more fiber rich for support

75% of spleen, where blood flows through loosely arranged sinuses
- stains lighter than white pulp since white pulp is lymphocyte rich


White pulp

Lymphocyte rich
less fiber rich

○ Darker than red pulp (because it is lymphocyte rich)


What do PALS that surround incoming arteriole in the spleen consist mainly of?

How are they different from nodules?


nodules: contain mostly B-cells


Do red blood cells or white blood cells move between the endothelium of the spleen?


RBC: enter red pulp space
WBC: entter through spleen


Are macrophages in the spleen easily stained? How?

macrophages of spleen ingest ink particles and readily visualized
- fewer in white pulp region


When do lymph nodes become activated in the secondary follicles?

A lymph node becomes activated when B-cells migrate to germinal centers in response to recognition of an antigen. (Get swelling of the lymph nodes)

- remember MZ trap antigen from circulation and present it to lymphocyte