Lymphoreticular System Flashcards
What is the function of the lymphoreticular system?
Reclaim lost fluid for return to the cardiovascular system
Absorbs and transports fatty acids and fats as chyle from the digestive system
Protect against pathogens and cancer cells
How are lymphocytes produced?
Made in bone marrow
2 types produced - B lymphocyte and T lymphocyte
Thymus produce T lymphocytes
Bone marrow produce B lymphocytes
B lymphocytes associated with plasma cells
T lymphocytes divide into suppressor, killer and helper
Explain the immune response of B lymphocytes
Initiated when B cells encounte antigens, which are triggered by B cell receptors
B cells then internalize the antigen and process it into smaller fragments, which are displayed on the surface of the B cell.
Helper T cells recognize these complexes and secrete cytokines to further activate the B cell.
Activated B cells undergo clonal expansion, proliferating and dividing into plasma cells and memory B cells.
Plasma cells produce antibodies which are specific to the antigen and form an antigen-antibody complex marking it for destruction.
Some activated B cells differentiate into memory B cells which provide a rapid secondary immune response if same antigen is encountered.
Explain the immune response of T lymphocytes
Cell-mediated immunity involves the recognition of antigens by T cells through the T cell receptor, activation by T cells, and clonal expansion.
Activated T cells are stimulated by antigen-presenting cells such as dendritic cells, macrophages, or B cells.
The population of T cells capable of recognizing and responding to the antigen is amplified- clonal expansion
Cytotoxic T cells (CD8+ T cells) directly kill infected or abnormal cells, while helper T cells secrete cytokines to regulate the immune response.
Regulatory T cells maintain immune homeostasis by suppressing excessive responses and preventing autoimmune reactions
What are the 5 types of white blood cells?
Neutrophil - multi lobed nucleus, granulocyte
Monocyte - horse shoe shaped nucleus, agranulocyte, larger than eosinophil
Basophil - granulocyte, granules obscure nucleus
Eosinophil - granulocyte, bilobed nucleus
Lymphocyte - agranulocyte, large round nucleus
Describe the spleen
oval shape
Acts as a filter for blood as part of the immune system
Red pulp - CT framework (trabeculae), contains reticular fibres, rich vascular supply filters blood
White pulp - periarteriolar lymphatic sheaths, white pulp responds to antigens and produces antibodies
Lymphoid follicles termed white pulp
Describe the lymph node
Spherical or kidney shaped
Encapsulated, deals with lymph-borne antigens
Outer curved boundary - lymphatic vessels enter
Hilum - lymphatics leave
Light area is medulla and dark area is cortex
Purple circle is a follicle (germinal center in follicle)
What are the 2 types of lymphatic tissue?
Discrete - organised into a space e.g lymph nodes, thymus, spleen
Diffuse - spread out e.g, mucosa associated lymphoid tissue.
Describe the thymus
Consists of 2 lobes connected by an isthmus
Function of thymus is to educate thymocytes that arrive from bone marrow
Cortex - intense thymocyte proliferation (increase in number) occurs here, pale pink areas are support networks of epithelial reticular cells
Medulla - specialised epithelial cells, dendritic cells and macrophages are present as the thymocytes move from the cortex to medulla
In medulla of thymus are concentric whorls of epithelial reticular cells
Whorl contains keratin in the middle - Hassall’s corpuscles.
Describe the immune response of macrophages
First cell to recognise and engulf antigens
Macrophages break down these substances and present the smaller proteins to T cells
Also produce cytokines which regulate activity of lymphocytes
How is lymph formed?
Lymph originates as fluid lost from capillaries
Collected in blind end lymphatic capillaries
Overlapping endothelial cells create one-way mini valves
Fluids, solutes driven into lymphatic capillary by pressure in interstitial space
