4. Lymphoid Organs Flashcards
What are Hassall corpuscles and where are they found?
Function unknow, they are structures found in the medulla of the human thymus, formed from eosinophilic type VI epithelial reticular cells arranged concentrically.
What type of cell does the Thymus protect and develop?
They protect T cells by the blood-thymus barrier.
Where in the lymph node can we find the most amount of B lymphocytes?
In the outer cortex of the nodules and germinal centers.
Where in the lymph node can we find the most amount of T lymphocytes?
In the inner cortex.
What are dendritic cells and where are they found?
They are the antigen-presenting cells of the lymph nodes.
What are high endothelial venules and where are they found?
They form the site of repopulation of lymph nodes and are found in the paracortical zone.
Which organ has a red pulp and a white pulp?
The spleen
What happens in the white pulp?
It consists of lymphoid tissue that ensheaths the central arteriers (periarterial sheath) along with the associated nodues and germinal centers. The periarterial sheath is populated by T lymphocytes. The peripheral white pulp and germinal centers are populated mainly by B lymphocytes.
What are the cords of Billroth?
They are splenic cords found in the red pulp of the spleen. Consisting of fibrils and connective tissue cells with a large population of monocytes and macrophages, these cords contain half of the human body’s monocytes as a reserve so that after tissue injury these monocytes can move in and aid locally sourced monocytes in wound healing.
Decribe the red pulp.
It is made of splenic cords and venous sinusoids. In disorders of erythrocyte shape and/or flexibility, such as hereditary spherocytosis, erythrocytes fail to pass through and get phagocytosed, causing extravascular hemolysis. Erythrocytes pass through the cords of Billroth before entering the sinusoids. The passage into the sinusoids may be seen as a bottleneck, where erythrocytes need to be flexible in order to pass through.
