Histology of the Thymus and Peripheral Lymphoid Organs Flashcards Preview

Blood and Lymph > Histology of the Thymus and Peripheral Lymphoid Organs > Flashcards

Flashcards in Histology of the Thymus and Peripheral Lymphoid Organs Deck (31)
Loading flashcards...
1
Q

Name three encapsulated lymphoid organs.

A
  1. Lymph Nodes
  2. Thymus
  3. Spleen
2
Q

What structures are considered primary lymphoid organs?

A

Bone marrow

Thymus

3
Q

How does lymph enter and exit a lymph node?

A

Lymph enters in the afferent lymphatic vessels into the subcapsular space

Then they exit through the efferent lymphatic vessels

4
Q

The lymph node is made up of three regions, what are they?

A

Cortex
Paracortex
Medulla

5
Q

What separates the cortex?

A

Trabeculae

6
Q

What is contained in the cortex?

A

Germinal centers full of active cell proliferation and apoptosis

Mostly B cells

Some macrophages

7
Q

What is the paracortex mostly comprised of?

A

T cells and some B cells

8
Q

What is contained in the medulla?

A

B cess, a few T cells and plasma cells

9
Q

Where do the blood vessels enter and exit?

A

At the hilum

10
Q

Why is the high endothelial venule important?

A

It is the site for recognition and diapedesis of lymphocytes from the blood into the lymphatic space of the node.

Contain selectins

11
Q

What occurs in the thymus?

A

Proliferation, differentiation and selection of thymocytes

12
Q

When does the thymus involution occur?

A

Around puberty

13
Q

What composes the cortex of the thymus?

A

More densely packed set of developing thymocytes having dark nuclei. It also stains darker

14
Q

Where can you find more mature thymocytes in the thymus?

A

In the less densely packed medulla.

15
Q

What kind of cells are found just beneath the capsule?

A

Blast cells that divide and give rise to other immature thymocytes

16
Q

Where can you find returning T cells in the thymus?

A

In the medulla.

17
Q

What other cell types can be found in the thymus?

A

Epithelial-like cells
dendritic cells
Macrophages

18
Q

Stromal cells are important in what type of thymocyte maturation process?

A

Positive and negative selection

They secrete various cytokines and unique thymus hormones important in thymocyte maturation

19
Q

Does the thymus contain reticular fibers?

A

No

20
Q

What are Hassl’s corpuscles and why are they important?

A

They are comprised of concentric layers of reticular cells

These cells produce thymus stromal lymphoprotein that is important in suppressing autoimmune events

21
Q

Where do arteries enter the thymus?

A

They enter through the outer capsule and penetrate into the thymus and bifucate within the connective tissue septa

22
Q

Describe the blood-thymus barrier.

A

The endothelial cells of the vessels have tight junctions and are surrounded by a region of connective tissue that is then ensheathed in endothelioreticular cells

23
Q

What are the main vessels going into and out of the spleen?

A

Splenic artery

Splenic vein

24
Q

What is a special feature of the central arterioles of the spleen?

A

The endothelium is discontinuous allowing RBCs, platelets, and WBC to leave circulation.

25
Q

Where is the bulk of lymphoid tissue found in the spleen?

A

They are found wrapped around the central arteriole in perarteriolar lymphoid sheath (PALS). Contain germinal centers

26
Q

Blood flows into _________ and more organized lymphoid tissue is found in the __________

A

Red Pulp

White pulp

27
Q

Loosely-arranged reticular fibers are primarily found in _________ pulp

A

Red

28
Q

Are macrophages found more in the red or white pulp?

A

Both

29
Q

Where are mucosal-associated lymphoid tissues found

A

Mostly in the digestive tract and respiratory system.

Ex: Tonsils, adenoids, appendix, Peyer’s patches

30
Q

Is MALT encapsulated?

A

No

31
Q

What is the role of M cells?

A

They deliver antigens to underlying lymphoid tissue