Lymphoid tissues Flashcards
What are the 3 sources of lymphocytes?
- Yolk sac
- Fetal liver
- Bone marrow
Where are the 4 sites of lymphocyte development?
- Thymus
- Bursa
- Peyer’s patches
- Bone marrow
Where are the 5 sites in which lymphocytes respond to antigens?
- Tonsils
- Spleen
- Lymph nodes
- Peyer’s patches
- Bone marrow
Where lymphocytes are generated and matured is known as?
Primary lymphoid tissue
Where does the production of stem cells occur?
Bone marrow
Where does specialisation occur?
Thymus
What is the role of secondary lymphoid tissue?
Where lymphocytes interact with antigen presenting cells
What happens to T-cells in the thymus?
- T lymphocyte maturation and selection
- T cells arrive as immature thymocytes and leave as mature T cells
Through which structure do T-cells gain access into the thymus?
Hassans Corpuscles
Describe the tissue arrangement of the thymus
- 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
Describe what happens to T-cells in the cortex and medualla
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
How does the thymus change as aging occurs?
More fatty and atrophied areas develop, it is smaller but still functional
Where do lymph nodes drain fluid?
Into afferent lymphatic vessels
Via what do lymphocytes recirculate into the blood from lymph nodes?
Afferent lymphatics and thoracic duct
Which tissue are of the lymph node contains high endothelial venules?
Paracortex
What is the function of high endothelial venules?
- Deals with naive T and B cells that haven’t dealt with an antigen
- This allows them passage into the lymph node
What is a germinal centre?
An area of discrete lymphocyte proliferation
What are the 3 functions of lymph?
- Drains intestinal fluid
- Transports dietary lipids
- Facilitates immune responses by draining antigens from tissues to lymph nodes and eventually the blood
What is the main key difference between the lymph system and the blood system?
Central pump in blood system but no pump in the lymph system so lymph drains slowly
What is the role of the spleen?
- Gives us systemic immunity
- Without a spleen there is nowhere for lymphocytes to recirculate so if reinfected there won’t be antibodies present
What is red and white pulp?
Red pulp = open sinusoids containing RBCs
White pulp = Lymphocytes
What colour does white pulp stain with H and E?
Blue
Where is mucosa-associated lymph tissue (MALT) found?
- GI tract
- Respiratory tract
- Genito-urinary tract
- Peyer’s patches
- Appendix
- Tonsils
Describe the structure of MALT
- Very dense areas of lymphocytes
- Dark blue stained
- Non-encapsulated
Where are Peyer’s patches located?
In ileal submucosa of the small bowel
Where in the Peyer’s patches is the site of antibody production?
Germinal centres
What is the mantle zone within the Peyer’s patch?
An area containing unresponding B-cells
How do antigens from the luminal environment get into the Peyer’s patch?
Domes containing microfolds capture antigens from the luminal environment and transfer them into the Peyer’s patch
