Lymphoid Organs Flashcards
What are the lymphoid organs?
Thymus
Lymph nodes
Tonsils
Spleen
Why is bone marrow not considered to be a lymphoid organ?
Lymphocytes are present in large numbers in bone marrow but are not the primary constituent of this tissue
The thymus is a primary lymphoid organ. What cells are programmed here?
T cells
Where are T and B cells produced?
Bone marrow
Where are B cells programmed?
Bone marrow
In which syndrome is there a congenital lack of a thymus leading to an incomplete immune system?
Di George’s syndrome
What is the definition of a lymphoid organ?
A collection of small lymphocytes surrounding by a delicate skeleton usually composed of reticular fibres
Describe mechanical filtration in the lymph node?
Lymph flows from the small afferent vessels to the large ‘tank’ which is the sub capsular sinus which results in a decrease in the speed of lymph flow which causes particles or bacteria present in the lymph to drop down onto the cells below
What is meant by biological filtration in lymph nodes?
Phagocytosis of debris by macrophages?
Where do macrophages exist within the lymph node?
In the sinuses
Where in the lymph node do T cells exist?
the deep cortex
Where in the lymph node do B cells exist?
Outer cortex an medullary cords
Describe the development of lymphoid nodules.
These develop when there is an active antibody response
The B cell which has the appropriate antibody corresponding to the antigen will begin to proliferate and form clones
this forms the lymphoid nodule
a condensation of small lymphocytes next to the antigen forms the cap of the nodule and the main body of the nodule (the germinal centre) is composed of larger lymphocytes
In the spleen, where is the cap of a lymphoid follicle found?
Next to the red pulp
Describe the distribution of T and B cells in the spleen?
T cells immediately surround the central artery in the white pulp
B cells exist outward for here
