Flashcards in DD Thymus and peripheral lymphoid organs Deck (18)
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?
-circular light bodies in the medulla
2 arteries that enter the thymus?
Are there afferent and efferent supply of lymph to the thymus?
No afferent, just efferent
Describe the blood and lymphatic drainage of the thymus
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
- has hassals corpuscles (circular bodies)
- less lymphocytes
- 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?
- efferent vessel
- efferent vessel
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
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
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
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