DD Thymus and peripheral lymphoid organs Flashcards Preview

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Flashcards in DD Thymus and peripheral lymphoid organs Deck (18):
1

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

2

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

Hassalls corpuscles
-circular light bodies in the medulla

3

2 arteries that enter the thymus?

Internal thoracid
inferior thyroid

4

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

No afferent, just efferent

5

Describe the blood and lymphatic drainage of the thymus

Arteries in,
Venous and efferent lymphatic drainage out.

6

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

difference in lymphocyte population and staining of their nuclei

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

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

7

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

8

Which vessels leave the lymph node? Thymus?

lymph node?
- efferent vessel
- artery
- vein

Thymus?
- efferent vessel
- vein

9

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

10

Do unchallenged lymph nodes contain germinal centers?

No

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

- unchallenged /primary follicles have no germinal center

11

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)

12

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

Spleen - many circulated Antibodies are produced here

13

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

14

White pulp

Lymphocyte rich
less fiber rich

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

15

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

How are they different from nodules?

T-cells

nodules: contain mostly B-cells

16

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

Both

RBC: enter red pulp space
WBC: entter through spleen

17

Are macrophages in the spleen easily stained? How?

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

18

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