Lymphoid tissues

Question 1

What are the 3 sources of lymphocytes?

Answer 1

• Yolk sac
• Fetal liver
• Bone marrow

Question 2

Where are the 4 sites of lymphocyte development?

Answer 2

• Thymus
• Bursa
• Peyer’s patches
• Bone marrow

Question 3

Where are the 5 sites in which lymphocytes respond to antigens?

Answer 3

• Tonsils
• Spleen
• Lymph nodes
• Peyer’s patches
• Bone marrow

Question 4

Where lymphocytes are generated and matured is known as?

Answer 4

Primary lymphoid tissue

Question 5

Where does the production of stem cells occur?

Answer 5

Bone marrow

Question 6

Where does specialisation occur?

Answer 6

Thymus

Question 7

What is the role of secondary lymphoid tissue?

Answer 7

Where lymphocytes interact with antigen presenting cells

Question 8

What happens to T-cells in the thymus?

Answer 8

• T lymphocyte maturation and selection

- T cells arrive as immature thymocytes and leave as mature T cells

Question 9

Through which structure do T-cells gain access into the thymus?

Answer 9

Hassans Corpuscles

Question 10

Describe the tissue arrangement of the thymus

Answer 10

• Encapsulated and split into lobules
• Each lobule has a cortex and medulla
• Cortex is dark staining and is densely populated with lymphocytes
• Medulla is less densely populated

Question 11

Describe what happens to T-cells in the cortex and medualla

Answer 11

Corex: Thymocytes mature to adult T-lymphocytes and then migrate to the…
Medulla: T-cells are presented with antigens and thymic selection occurs where survivors become functional T-cells

Question 12

How does the thymus change as aging occurs?

Answer 12

More fatty and atrophied areas develop, it is smaller but still functional

Question 13

Where do lymph nodes drain fluid?

Answer 13

Into afferent lymphatic vessels

Question 14

Via what do lymphocytes recirculate into the blood from lymph nodes?

Answer 14

Afferent lymphatics and thoracic duct

Question 15

Which tissue are of the lymph node contains high endothelial venules?

Answer 15

Paracortex

Question 16

What is the function of high endothelial venules?

Answer 16

• Deals with naive T and B cells that haven’t dealt with an antigen
• This allows them passage into the lymph node

Question 17

What is a germinal centre?

Answer 17

An area of discrete lymphocyte proliferation

Question 18

What are the 3 functions of lymph?

Answer 18

• Drains intestinal fluid
• Transports dietary lipids
• Facilitates immune responses by draining antigens from tissues to lymph nodes and eventually the blood

Question 19

What is the main key difference between the lymph system and the blood system?

Answer 19

Central pump in blood system but no pump in the lymph system so lymph drains slowly

Question 20

What is the role of the spleen?

Answer 20

• Gives us systemic immunity

- Without a spleen there is nowhere for lymphocytes to recirculate so if reinfected there won’t be antibodies present

Question 21

What is red and white pulp?

Answer 21

Red pulp = open sinusoids containing RBCs

White pulp = Lymphocytes

Question 22

What colour does white pulp stain with H and E?

Answer 22

Blue

Question 23

Where is mucosa-associated lymph tissue (MALT) found?

Answer 23

• GI tract
• Respiratory tract
• Genito-urinary tract
• Peyer’s patches
• Appendix
• Tonsils

Question 24

Describe the structure of MALT

Answer 24

• Very dense areas of lymphocytes
• Dark blue stained
• Non-encapsulated

Question 25

Where are Peyer’s patches located?

Answer 25

In ileal submucosa of the small bowel

Question 26

Where in the Peyer’s patches is the site of antibody production?

Answer 26

Germinal centres

Question 27

What is the mantle zone within the Peyer’s patch?

Answer 27

An area containing unresponding B-cells

Question 28

How do antigens from the luminal environment get into the Peyer’s patch?

Answer 28

Domes containing microfolds capture antigens from the luminal environment and transfer them into the Peyer’s patch