Lymphatics Part 2

Question 1

What type of collagen is in lymph nodes? Whats the benefit?

Answer 1

Type 3 collagen (Reticular Fibers); Open fiber network maximizes cell interactions

Question 2

What is the hilum of a lymph node?

Answer 2

A miniscule lymphatic artery/vein enter and exit here.

Question 3

Describe HEVs

Answer 3

HEV endothelium is simple cuboidal and thicker than normal endothelium; Allows lymphocytes to leave blood circulation and enter the lymph node. (Diapedesis)

Question 4

Describe the Superficial cortex of a lymph node

Answer 4

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.

Question 5

What do B cells do once they’re in the cortex?

Answer 5

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.

Question 6

What is the relationship between the number of follicles and the intensity/duration of antigenic challenge?

Answer 6

They are directly related.

Question 7

Describe the mantle zone?

Answer 7

The mantle zone contains unactivated, naive mature b cells that were originally in the primary follicle from which the secondary follicle evolved.

Question 8

Histologically describe the mantle zone?

Answer 8

The darker staining perimeter around the lighter staining germinal center; Germinal center + Mantle zone = Follicle

Question 9

Where can plasma cells be found?

Answer 9

Initially in the germinal centers; Mature plasma cells are in the medullary cords.

Question 10

Describe the deep cortex (Paracortex).

Answer 10

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.

Question 11

What other cells move to the deep cortex?

Answer 11

Dendritic cells move there to present antigen to mature, naive t cells.

Question 12

Describe the relationship between afferent lymph vessels and efferent lymph vessels

Answer 12

There are multiple afferent lymph vessels as opposed to a single efferent lymph vessel.

Question 13

Summarize the lymph circulation

Answer 13

Afferent vessel, Subcapsular sinus, trabecular sinus, medullary sinus, efferent vessel. Repeat

Question 14

What is the major difference between the spleen and the lymph node?

Answer 14

Antigens are delivered by blood, not lymph.

Question 15

Can the spleen perform hematopoiesis?

Answer 15

Yes if under extreme stress for more blood cells.

Question 16

Describe the spleen parenchyma.

Answer 16

A loose meshwork of reticular fibers (Type 3 collagen); Divided into red and white pulp. 3 to 1 ratio.

Question 17

Describe the white pulp histologically.

Answer 17

Looks basophilic due to high to lymphocyte density and antigen presenting cells.

Question 18

What is the marginal zone?

Answer 18

The boundary region between white pulpls lymphoid follicle and surrounding red pulp.

Question 19

Histologically describe the marginal zone.

Answer 19

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.

Question 20

What is a periarterial lymphatic sheath?

Answer 20

T-cell zone of spleen; A cylindrical aggregation of mostly T cells immediately surrounding a microscopic central artery.

Question 21

Discuss the open circulation in the spleen.

Answer 21

The bulk flow of blood from the terminal arterial capillaries through the splenic cords and splenic sinuses; Blood is not continuously in specific vessels.