Lymphatics Part 2 Flashcards
What type of collagen is in lymph nodes? Whats the benefit?
Type 3 collagen (Reticular Fibers); Open fiber network maximizes cell interactions
What is the hilum of a lymph node?
A miniscule lymphatic artery/vein enter and exit here.
Describe HEVs
HEV endothelium is simple cuboidal and thicker than normal endothelium; Allows lymphocytes to leave blood circulation and enter the lymph node. (Diapedesis)
Describe the Superficial cortex of a lymph node
The B cell zone; Once naive B cells move out of the HEV they move through the paracortex and into the cortex in response to chemokines.
What do B cells do once they’re in the cortex?
They form follicles; Primary follicles are mature-naive b cells. Secondary follicles are mature b cells that have been activated by antigen. They form a germinal center; There are more secondary follicles than primary.
What is the relationship between the number of follicles and the intensity/duration of antigenic challenge?
They are directly related.
Describe the mantle zone?
The mantle zone contains unactivated, naive mature b cells that were originally in the primary follicle from which the secondary follicle evolved.
Histologically describe the mantle zone?
The darker staining perimeter around the lighter staining germinal center; Germinal center + Mantle zone = Follicle
Where can plasma cells be found?
Initially in the germinal centers; Mature plasma cells are in the medullary cords.
Describe the deep cortex (Paracortex).
T cell zone; Between the superficial cortex and the medulla. Once they exit HEVs, t cells move here due to chemotaxis; Similar to B cell movement.
What other cells move to the deep cortex?
Dendritic cells move there to present antigen to mature, naive t cells.
Describe the relationship between afferent lymph vessels and efferent lymph vessels
There are multiple afferent lymph vessels as opposed to a single efferent lymph vessel.
Summarize the lymph circulation
Afferent vessel, Subcapsular sinus, trabecular sinus, medullary sinus, efferent vessel. Repeat
What is the major difference between the spleen and the lymph node?
Antigens are delivered by blood, not lymph.
Can the spleen perform hematopoiesis?
Yes if under extreme stress for more blood cells.
Describe the spleen parenchyma.
A loose meshwork of reticular fibers (Type 3 collagen); Divided into red and white pulp. 3 to 1 ratio.
Describe the white pulp histologically.
Looks basophilic due to high to lymphocyte density and antigen presenting cells.
What is the marginal zone?
The boundary region between white pulpls lymphoid follicle and surrounding red pulp.
Histologically describe the marginal zone.
More eosinophilic than the red pulp because of the pooling of blood; Possesses vascular spaces of blood called marginal sinuses. Contains B cells and macrophages, T cells, and APCs.
What is a periarterial lymphatic sheath?
T-cell zone of spleen; A cylindrical aggregation of mostly T cells immediately surrounding a microscopic central artery.
Discuss the open circulation in the spleen.
The bulk flow of blood from the terminal arterial capillaries through the splenic cords and splenic sinuses; Blood is not continuously in specific vessels.
