Lymphoid Tissue Flashcards
What are two different systems that provide us with immunity
- Innate immune system (lacks immunological memory)
2. Adaptive immune system (high specificity and memory)
Name the components of the innate immune system
- Barriers against invasion (skin)
- Phagocytes (macrophages and neutrophils)
- Complement (plasma proteins)
- Extracellular killers (lymphocytes and eosinophils)
What is the major role of the innate immune system
Destruction of foreign invaders; ability to distinguish ‘self’ from ‘non-self’ is absolutely critical
What is the adaptive immune system based on
Lymphocytes and a vast array of genetically determined cell surface receptors
How are lymphoid organs connected to one another
Through communication between the blood vascular and lymph vascular systems
What are primary lymphoid organs, and where are they in humans
Sites of lymphocyte production and maturation: bone marrow and thymus
What are secondary lymphoid organs, and what are examples in humans
Sites to which lymphocytes migrate and where they aggregate in large number: spleen, lymph nodes, and lymph nodules
What are the 3 principal forms of lymphocytes
- B cells (produce antibodies)
- T cells (participate in cellular immunity)
- Natural killer cells (killer virus-infected cells, and some tumour cells)
What is the term used for the process by which cells of the immune are identified
Done using immunohistochemistry, termed Cluster Designation (CD) molecules
How many lobes form the thymus, and what separates them
It has two lobes subdivided by septa
Describe the structure of the lobules
- Outer cortex that is highly cellular
2. Less cellular inner medulla
What part of the thymus lobule stains darker
The highly cellular cortex
What cells exist within the thymus
- T cells
- Epithelioreticular cells
- Macrophages (cortex)
What % of immature T cells will ‘fail’ the process of maturation
Around 98%
Describe the movement of mature T cells through the thymus
Cortex -> medulla -> blood vessels
Name the whorls of epithelial cells with a keratin core that accumulate in the thymus’ medulla
Hassall’s corpuscles
Describe 3 functions of the lymphatic system
- Drainage of lymph into the vascular system
- Surveillance of tissue for signs of antigens from foreign invaders
- Delivery of absorbed fats from the small intestine into the vascular system
What are lymphatic vessels lined with interiorly
Endothelium
What are lymph nodes
Encapsulated, highly organised structures interposed along larger lymph vessels
How do lymphocytes enter the lymph nodes
- Via the incoming lymph
2. From the bloodstream
Describe the structure of a secondary follicle within a lymph node
- Germinal centre (less densely packed; dividing B cells)
2. Surrounded by a mantle zone (resting B cells)
What region of a lymph node is populated mostly by T cells
The paracortical region; contains cuboidal epithelium
What cells exist within the medulla of a lymph node
- Plasma cells
2. Macrophages
What does GALT, MALT, and BALT stand for
GALT = gut-associated lymphoid tissue MALT = mucosa-associated lymphoid tissue BALT = bronchial-associated lymphoid tissue
Within the tonsils, what are the deep crypts lined with
Stratified squamous epithelium and the lymphoid follicles
What are the functions of the spleen
- Produce immune response against blood-borne antigens
- Removal of particulate matter and aged blood cells (mostly RBCs)
- Production of blood cells during foetal life
Describe the structure of the spleen
Whitish nodules 0.5-1.0mm in diameter (white pulp) embedded in deep red tissue (red pulp)
How does the spleen recognise old from young red blood cells
Blood cells have to pass through the complex vasculature (requires them to deform); old red blood cells cannot do this and will be phagocytosed by macrophages
