Lecture 16- Lymphatic System Flashcards
Immune system
Set of defences to prevent or reduce damage or disease
Innate immunity
Set of defences that are present from birth and recognize common characteristics of many pathogens
Adaptive immunity
Involves T and B lymphocytes that can help the immune response learn, adapt and remember previous pathogens
What is interstitial fluid that does not circulate back into the blood is collected by?
Lymphatic vessels
Three parts the lymphatic system consists of:
Network of lymphatic vessels
Lymph
Lymphatic cells and organs
Lymphatic capillaries
Found between tissue cells and blood capillaries in loose connective tissue
Large molecules can pass through
Flow into collecting lymphatic vessel and carry the lymph to lymphatic trunks
Lymphatic trunks
Drains fairly large areas of the the body and eventually empty the lymph back int the circulatory system via the right lymphatic duct or thoracic duct
Lymphatic vessels
Low pressure vessels that use the same mechanisms as veins to return the lymph to circulatory system
Skeletal muscle compression
Pressure changes during breathing
Valves to prevent backflow
Lymphocytes
Arise in red bone marrow and mature into T cells (thymus) or B cells (bone marrow)
T cells
Manage immune responses and some also attack and destroy infected cells
B cells
When they encounter an antigen they can activate into plasma cells which secrete antibodies, which mark antigens for destruction by phagocytosis or other means
Natural killer cells
In at immune cells that are cytotoxic (cell killing)
Macrophages
Can act as phagocytes and help to activate T lymphocytes
Dendritic cells
Found in lymphoid tissue, play a role in t lymphocyte activation (reporter cells)
Reticular cells
Produce reticular fibres that make up the stroma, the network that supports the other cells types in lymphoid tissues (maintains lymph nodes)
Lymphoid tissues
house and provide a proliferation site for lymphocytes and furnish an ideal surveillance site for lymphocytes and macrophages.
Diffuse lymphoid- found in nearly every body organ
Lymphoid follicles- may form part of larger lymphoid organs
Lymph nodes
act as filters to remove and destroy micro-organisms and other debris for the lymph before it is transported back to the bloodstream.
Buboes
inflamed, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy.
Spleen
Largest lymphoid organ locate din upper left sid of abdominal cavity
main function is to remove old and defective red blood cells and platelets as well as foreign matter and debris from the blood. also provides site for
lymphocyte proliferation and immune surveillance.
Surrounded by fibrous capsule and contains bot lymphocytes found in white pulp and macrophages found in red pulp
White pulp
Site where immune function occurs
Red pulp
Site where old blood cells and bloodborn pathogens are destroyed
Mucosa-associated lymphoid tissues (MALT)
set of lymphoid tissues located in mucous membranes throughout the body.
Tonsils
simplest lymphoid organs, forming a ring of lymphoid tissue around the opening to the
pharynx.
They gather and remove many of the pathogens entering the pharynx in food or inhaled air.
Tonsillar crypts
pockets of epithelium that catch bacteria and food particles to train immune cells against potential pathogens.
Peyers patches
Clusters of aggregated lymphoid nodules
found in the wall of the ileum (the distal portion of the small intestine).
Appendix
located off the first part of the large intestine and contains large numbers of lymphoid follicles.
It appears to play a role in maintaining the normal flora of the intestines, rather than simply trying to destroy them.
Thymus
secretes hormones that cause T lymphocytes to become immunocompetent.
most active during childhood, stops growing during adolescence and gradually atrophies in adulthood. continues to function but more slowly.
How does the thymus differ from other lymphoid organs?
It has no B cells and, therefore, no follicles.
It is not directly involved in fighting antigens.
The stroma of the thymus consists of epithelial cells, not reticular fibres, to contain immature T lymphocytes.
Major histocompatibility complex (MHC) proteins
Expressed on the outside of cells
T lymphocytes use MHCs to check on health of cells
What kind of proteins do all nucleated cells have?
Class I MHC proteins.
Cells present a few cytoplasmic proteins on MHC I so T lymphocytes can see if the cell is infected.
What kind of protein do dendritic cells, macrophages and B cells have?
Class II MHC proteins.
Pathogens that get engulfed by these cells are digested into smaller pieces and antigens are presented on MHC II.
Immunocompetence
Recognition of specific antigens
Self tolerance
Ensuring they do to attack the body’s own cells
Positive selection
in the outer cortex of the thymus, which allows only T lymphocytes that recognize MHC proteins to survive.
Negative selection
in the inner medulla of the thymus, which allows only T cells that do not recognize self-antigen proteins to survive.
What is the thymus made up of?
made up of thymic lobules containing an outer cortex of rapidly dividing T cells and an inner medulla where self-reactive T cells are removed.
