Flashcards in Histology of the Lymphoreticular System Deck (55)
What are the organs of the lymphoreticular system?
Thymus, lymph node, mucosa-associated lymphoid tissue (MALT), spleen
The immune system provides highly specific responses to what specifically?
To antigens with the destruction of the antigen
What was the original definition of an antigen?
Any molecule that binds specifically to an antibody
What does the term antigen now also refer to?
Any molecule or molecular fragment that can be bound by a major histocompatability complex (MHC) and presented to a T helper cell
What is the function of a MHC - major histocompatability complex?
The function of MHC molecules is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells.
What are the the types of lymphocytes?
B lymphocytes and t lymphocytes
What is the function of the b lymphocytes?
To produce antibodies
What is the function of the t lymphocytes?
They have several subtypes and act as suppressor cells, cytotoxic cells and helper cells
What are antigen presenting cells?
They include macrophages and the b lymphocytes control the activation of the t cells. An antigen-presenting cell is a cell that displays antigen complexed with major histocompatibility complexes (MHCs) on their surfaces
Why are the b lymphocytes called b lymphocytes?
Because they are formed from a stem cell, into a pre-b cell and the pre-b cell matures into a fully functional b cell in the red bone marrow
Why are the t lymphocytes called t lymphocytes?
Because they are formed from a stem cell into a pre t cell in the red bone marrow. but then the pre-t cell matures into a fully functional t cell in the thymus
Roughly what percentage of white blood cells in circulation are lymphocytes?
The number of lymphocytes in circulation increase in response to what?
In response to a viral infection
How would you describe lymphocytes under a microscope
they have a round/oval nuclei with dense chromatin and nucleoli which are not usually visible and often very little cytoplasm
How does the size of a lymphocyte compare to the size of red blood cells?
red blood cells are about 7 microns in diameter - about the size of a lymphocyte nucleus
What are the two types of lymphocytes?
t and b
what are the three types of t lymphocyte?
t helper cells, cytotoxic t cells and suppressor t cells
what do t helper cells do
they help other lymphocytes perform functions
what do cytotoxic t cells do
they kill virally infected and malignant cells
what do suppressor t cells do
they switch off the immune system when the stimulating antigen is removed
what do b lymphocytes do
they produce antibodies following maturation to plasma cells
what is a plasma cell
a fully differentiated B-lymphocyte (white blood cell) which produces a single type of antibody.
what types of cells are included in the antigen presenting cells category
macrophage monocyte type cells and dendritic cells
what do antigen presenting cells do?
the antigen is taken up by the apc and processed. processed antigen is then bound to a major histocompatability complex and the mhc-peptide complex is exposed to the outside world
how would you describe the dendritic cell morphology
finger like projections
what are the four organs of the lymphoid system
thymus, lymph nodes, mucosa-associated lymphoid tissue, spleen
what is the thymus
a flattened lymphoid organ
where is the thymus located
in the upper anterior mediastinum and lower part of the neck
when is the thymus most active and when does it undergo involution
most active during childhood, heaviest at puberty and then undergoes involution