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Flashcards in Lymphatic system Deck (63)
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1

primary organs and their function

-bone marrow
-thymus
-cloacal bursa (birds only)
-aggregated lymphoid nodules in small intestines (peyer's patches)
-generate lymphocytes from progenitor cells

2

secondary organs and their function

-lymph nodes
-spleen
-mucosal associated lymphoid tissue
-sites of lymphocyte activation/differentiation in context of immune response

3

function of lymphatic system

-to protect the body against pathogenic organisms and their products
-help in removal and disposal of cells undergoing natural or induced degenerations

4

mechanisms of action and the cells in which they occur

-phagocytosis (macrophages)
-production of immunologically competent cells (antigen presenting cells: dendritic cells, macrophages, b cells; and b/t lymphocytes)

5

fixed macrophages can be found in

sinusoids of the liver, spleen, and lymph nodes, as well as the reticulum of bone marrow

6

free macrophages can be found in

blood, lungs, and serous cavities

7

antigen presenting cells include what cells? what is their function

-dendritic cells, macrophages, and b-cells
-captre, process, and present fragments from extracellular antigens on MHC II

8

B cells are lymphoid stems cells differentiating where? Where to T cells form?

-bursa or bone marrow for b-cells
-thymus for t-cells

9

primary lymphatic organs functions specifics

-where t and b cells originate and their unique features established
-access by antigen is strictly controlled by barriers
-apoptotic elimination of self-reactive cells
-released to circulation to sites where antigen encountered (aka secondary lymphoid)

10

bone marrow is the source of

pluripotent stem cells, which become B and T cells
-background of stromal cells as well, which become macrophages

11

Cloacal bursa functionally equivalent to what

-dorsal wall of cloaca
-functionally equivalent to mammalian bone marrow for B cell differentiation

12

cloacal bursa: difference between dark cortex and light medulla

dark cortex: densely packed small lymphocytes
light medulla: lymphocytes, macrophages, reticular epithelial cells

13

Thymus location and function

-located in mediastinum just cranial to heart
-composed of epithelial reticulum (network) and lymphocytes
-lymphocytic stem cells migrate from bone marrow
-fill spaces btw reticular epithelial cells of developing organ
-site of T-cell development

14

thymic cortex

-stains much darker than thymic medulla due to greater number of lymphocytes present
-area of positive selection ("good lymphocytes")
-tingible body macrophages that frequent near the medulla to phagocytise and eliminate dead T cells

15

Thymic Medulla

-contains epithelial reticular cells in addition to lymphocytes
-area of negative selection ("bad" lymphocytes-autoreactive)
-some medullary reticular epithelial cells form thymic corpuscles or Hassall's corpuscles

16

thymic corpuscles

-large central calcified or degenerated cells surrounded by concentric circles of keratinized cells
-characteristic/notable aspect of thymus

17

blood supply of thymus

-arteries enter the thymus at the corticomedullary juntion within the connective tissue septa
-divides into arterioles within the septa
-branch into capillary network in the cortex

18

cortical capillaries of thymus

-forms the blood thymus barrier consisting of
-continuous endothelium
-perivascular connective tissue
-sheath of epithelial reticular cell processes

19

blood thymus barrier function

decreases antigen access to thymus, limits interference with positive T cell selection

20

educated T cells

-leave the thymus through postcapillary venules at the corticomeduulary junction
-enter blood, settle in T cell areas of secondary lymphatic tissue

21

Thymic involution

-thymus is active in young animals, involutes after sexual maturity (involution = shrinkage)
-gradual depletion of lymphocytes
-replacement by adipocytes

22

secondary lymphatic organs morphology/function

-network of organs, aggregated lymphatic tissue and cells
-linked by lymphatic vessels and blood vessels
-critical in innate/adaptive immunity
-filter mechanisms such as cells

23

lymph nodes function

-filter antigens from lymph before returning it to bloodstream
-ONLY lymphatic organ with both afferent and efferent lymph vessels and sinuses containing lymph

24

lymph node consists of three parts

-capsule, cortex, medulla, and hilus

25

lymph node cortex

-primary and secondary follicles rich in b-cells
-paracortical tissue rich in t-cells
-high endothelial blood vessels
-subcapsular sinus

26

lymph node medulla consists of

medullary cords and sinus

27

hilus

-slight indentation of lymph node
-arteries enter and efferent lymphatics and veins leave at hilus

28

lymph node capsule

-dense, irregular connective tissue
-(ruminants have smooth muscles cells too)
-trabeculae of capsule extend into cortex and medulla

29

trabeculae of lymph nodes

-extend from capsule into cortex and medulla
-structural support, contain blood vessels and nerves, and are surrounded by sinuses

30

lymph node stroma

-reticular cells and fibers that support lymphocytes, macrophages, and plasma cells