Secondary lymphoid organs

Other than B and T lymphocytes, what other cells are present in lymph nodes?

1. Reticular cells - synthesize type III collagen 2. Dendritic cells - efficient antigen presenting cells 3. Macrophages 4. Follicular dendritic cells- trap antigens in lymph fluid on thin cytoplasmic processes; cytoplasmic processes interdigitate between B cells in germinal centers (not antigen presenting cells)

What are the secondary lymphoid organs?

1. diffuse lymphoid tissue/ lymphoid follicles/tonsils 2. lymph nodes 3. spleen 4. bone marrow

what lymphocytes are most prevalent in lymphatic follicles?

B cells

The superficial cortex of lymph node is mostly composed of what kind of lymphocytes and in what arrangement?

B cells closely packed in follicles

from the sinuses how does blood from the spleen travel?

Blood from sinuses drain into trabecular veins that converge and leave the spleen via the splenic vein and into the circulation

secondary lymphatic organ: lymph nodes

ENCAPSULATED organs located along the lymphatic vessels. Has a dense connective tissue capsule. Composed of afferent (convex) and efferent lymph vessels along with blood supply (concave/hilum). Has superficial and deep cortex, and medulla. https://www.youtube.com/watch?v=LnqL46lKVec https://www.youtube.com/watch?v=EEP0PYEWcwU https://www.youtube.com/watch?v=HjvCv3syWq4

what surrounds the central artery in the white pulp of the spleen?

PALS-Periarterial Lymphatic Sheath - sheath of lymphocytes (mostly T-cells)

compare and contrast primary vs secondary follicles

Primary follicles - inactivated, young follicles;contain chiefly small lymphocytes . Secondary follicles - activated bc have responded to antigen; have a lighter staining center;are larger than primary due to the presence of actively dividing lymphocytes. secondary follicles will have GERMINAL CENTERS (light stain and larger)

How do lymphocytes from the blood migrate into the lymph node and where is this located?

T and B cells migrate from the blood into the HEV (high endothelial venules) of the lymph node. This is located in the DEEP CORTEX

The deep cortex of the lymph node is mostly composed of what kind of lymphocytes?

T cells

what composes the stroma of lymph nodes?

Type III collagen and ground substance

secondary lymphoid organ: diffuse lymphatic tissue

accumulations of non-encapsulated lymphatic tissue (i.e., lymphocytes and related cells) found in the lamina propria and submucosa of the GI, RESPIRATORY, AND GENITO-URINARY TRACT. generally referred to as MALT (Mucous-Associated Lymphatic Tissue) and sometimes also as GALT (Gut-Associated Lymphatic Tissue) when referring to the GI tract.

what are peyer's patches?

aggregates of lymphatic follicles that are ALWAYS found in the mucosa of the ileum

what composes the stroma of the spleen?

branched reticular cells and reticular fibers (type III collagen)

secondary lymphoid organ: lymphatic follicles

concentrations (usually ovoid in shape) of lymphocytes that are NOT ENCAPSULATED and commonly seen in the lamina propria and submucosa of the GI (ileum, appendix, cecum), respiratory and genito-urinary tract.

secondary lymphatic organ: spleen

contains a dense connective tissue capsule and trabeculae that extends into the spleen has a hilus where the splenic artery and vein exist white pulp: lymphatic region

Lymphocytes cross the HEV of the lymph node by migrating between the cells, a process known as....

diapedesis

what is the closed circulation theory of the spleen

holds that the capillaries empty directly into the sinuses (in other species).

what is the open circulation theory of the spleen

holds that the capillaries end prior to the sinuses and blood enters the reticular network of the red pulp. Blood then enters the sinuses through the endothelial pores. (This is the 'human' way)

ENCAPSULATED secondary lymphatic organs

lymph nodes spleen

secondary lymphatic organs that all contain reticular fibers (type III collagen)

lymph nodes spleen bone marrow

the NON encapsulated secondary lymphatic organs are

lymphatic tissue lymphatic follicles

The ____________ ___________ is at the periphery of the white pulp separating white pulp from red pulp.

marginal zone

where are most antigens filtered in the spleen?

marginal zone

what portion of the lymph node is made up of medullary cords separated by sinuses?

medulla (inner most portion of the lymph node)

what happens within secondary lymphoid organs?

naive lymphocytes can come into contact with their antigens and become activated which leads to proliferation and differentiation.

what are some distinguishing histological characteristics of the tonsils?

pharyngeal- contains serous and mucous glands also can contain respiratory epithelium. lingual- contains tongue muscle palatine-contains deep crypts

what composes splenic nodules?

small aggregations of lymphocytes (i.e., follicles) made up of predominantly of B cells.

what is the blood supply of the white pulp of the spleen?

splenic artery -> trabecular artery -> CENTRAL ARTERY

what does the central artery give off to provide blood supply to other portions of the spleen?

supplies marginal zone with branches supplies red pulp with penicillar arterioles

what surrounds the penicillar arterioles of the red pulp?

surrounded by an aggregation of macrophages known as PAMS (Periarterial Macrophage Sheath)

the PARTIALLY encapsulated lymphatic tissue containing follicles are...

tonsils

what are tonsils ?

tonsils are PARTIALLY encapsulated lymphatic tissues containing follicles. The three tonsils (pharyngeal, lingual, palatine form Waldeyer's ring and the surface of these tonsils are covered by stratified squamous epithelium. All three tonsils contain mucous glands.