Lymphoid Tissues

Front 1

describe the tissues of the lymphoids

Back 1

primary components are marrow and thymus. Capsulated structures include lymph nodes, thymus, spleen, tonsils. Diffuse lymph tissues include lymph nodules, MALT, GALT, and BALT. Cells include lymphocytes, macs, APC's, langerans of skin, M cells, mast cells, granulocytes

Front 2

describe the lymph nodule

Back 2

AKA follicle. Collection of B cells. Primary nodule does not have dividing B cells. Secondary nodules has stimulated B cells with a light staining germinal center where the cells are dividing. Nodules are not present in bone marrow and thymus.

Front 3

describe the flow of lymph

Back 3

1. blind ending capillaries form a net. 2. lymph vessels with valves. 3. afferent vessels enter the node. 4. through the node. 5. efferent vessels leave node. 6. lymph trunks - 4 paired (jugular, subclavian, bronchomediastinal, lumbar) and 1 single (intestinal). 7. lymph ducts: thoracic duct begins with cisterna chyle, drains left half of the body and the right half below the diaphragm, ends in left subclavian vein; right lymphatic duct drains right half above diaphragm and ending in right subclavian

Front 4

describe the lymph node components

Back 4

1. ct capsule where afferent lymph vessels enter. 2. cortex with nodules. 3. deep cortex which is the site of high endothelial postcapillary venules with no intercellular tight junctions and where recirculating lymphocytes leave blood circulation. 4. medulla with medullary cords of lymphocytes, plasma cells and macs. 5. hilum where blood vessels enter and leave and efferent vessels leave. 6. sinuses - subcapsular, cortical, medullary in which macs are located. these trap and present antigens to recirculating lymphocytes

Front 5

describe the location of cells within the lymph node.

Back 5

B cells are located in nodules in cortex. T cells are in deep cortex (paracortex) and between nodules in the cortex. Medullary cords consist mainly of B cells, plasma cells, and macs. Sinuses have macs and endothelial cells.

Front 6

describe how lymph, antigenes and lymphocytes get to the nodes

Back 6

lymph with antigens and lymphocytes enter via afferent vessels into subcapsular sinus, passes through cortical sinuses into the medullary sinuses. leaves these sinuses via efferent vessels at the hilum. Macs trap antigens and note lymphocytes also enter deep cortex via postcapillary venules and leave via the efferent lymph vessels

Front 7

describe the GALT

Back 7

located in the lamina propria of mucosa and includes Peyer's patches (lymph nodules). M (microfold) cells which are APCs replace the typical epithelium of gut over these patches

Front 8

describe the components of the thymus.

Back 8

thin ct capsule which sends septa with blood vessels into the thymus dividing it into lobes and lobules. Cortical region of densely packed lymphocytes - area where T cells are programmed. Medullary region is loosely packed area containing thymic (hassall) corpuscles. medullary area is continuous between lobes and is where blood vessels enter and leave the parenchyma. capillaries enter cortex from medulla. endothelial cells of cortical capillaries have tight junctions forming a blood thymus barrier

Front 9

embriologically, where does the thymus come from?

Back 9

originates from pharyngeal pouches and the supporting tissue for lymphocytes consists of this endodermal epithelium (reticular epithelial cells) not fibroblasts.

Front 10

how do mature T cells exit the thymus?

Back 10

via venules of medulla and efferent lymphatics

Front 11

what lymph structures does the thymus not have?

Back 11

lymph nodules or afferent vessels

Front 12

describe the components of the spleen.

Back 12

very thick ct capsule which sends thick trabecula into the organ. Red pulp. White pulp. Marginal zone between red and white pulp

Front 13

describe the vascular flow in the spleen.

Back 13

splenic artery gives rise to trabecular artery which gives rise to central arteries (arterioles) invested by PALS (periarterial lymphatic sheath of T cells) and nodules. Here is where it gets hairy. Penicillar arteries give rise to sheathed caps formed by macs instead of endothelium which empyt into red pulp between sinusoids (open circulation). alternative route is penicillar arteries to pulp arterioles to mac sheathed arteries to terminal arterial capillaries which drain into sinusoids (closed circulation) or into red pulp between sinusoids (open circulation). to enter the sinusoids, RBC's must deform or they are destroyed by macs. splenic sinusoids drain into pulp veins which drain into trabcular veins into the splenic vein.

Front 14

describe white pulp.

Back 14

consists of diffuse and nodular lymphoid tissue, PALS, and nodules (along central artery)

Front 15

describe red pulp.

Back 15

consists of sinusoids supported by reticular tissue (splenic cords). Sinusoids: have long endothelial cells seperated by intercellular spaces through which RBC must deform and pass. Splenic cords contain reticular cells (fibroblast), blood cells, plasma cells, and macs

Front 16

describe the splenic marginal zone.

Back 16

located at the periphery of the PALS and lymph nodules. Receives blood fom cap loops from central artery. 1st site where blood contacts splenic parenchyma. Has many macs and is an area where T and B cells enter the spleen before going to their specefic locations

Front 17

describe the functions of the spleen.

Back 17

immunological response against blood borne antigens. Filters blood removing particular matter and aged or defective blood cells, particularly RBCs. Provides hematopoiesis in normal fetuses and adults with certain diseases

Front 18

describe the architecture of the palantine tonsils

Back 18

lined with stratified squamous epi and has deep crypts where bacteria can hide and grow

Front 19

describe the architecture of the pharyngeal tonsil

Back 19

covered with pseudostratified ciliated epi, no crypts, only pleats

Front 20

describe the architecture of the lingual tonsils

Back 20

have many crypts covered with stratified squamous epi on posterior surface of the tongue. Crypts are continually washed out by mucous glands which empty into the base of the pits