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Vet Microanatomy 1 > Lymphatic system > Flashcards

Flashcards in Lymphatic system Deck (63):
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

31

lymph vessels and sinuses

-afferent lymph vessels enter lymph node at several places along the capsule
-open into subcapsular sinus
-afferent and efferent lymph vessels have valves (thus one way flow of lymph)
-cortical sinusses arise from subcapsular sinus, follow trabeculae to form medullary sinuses

32

medullary sinuses

-formed by cortical sinuses from subcapsular sinus
-open network of channels
-converge toward hilus
-open into efferent lymph vessels, all lymph leaves through efferent

33

major arteries enter the hilus to supply either the...

-medullary cords and cortex; have high endothelial venules, the site of lymphocytes extravasation
-or supply the trabeculae and supply the connective tissue and capsule of the region

34

path through lymph node/vessels

-afferent vessel -> marginal/subcapsular sinuses -> cortical/trabecular sinuses -> medullary sinuses -> efferent vessel

35

when stimulated by antigens, primary lymphoid follicles...

-change their histological morphology to secondary lymphoid follicles, possessing a marginal zone and germinal center

36

T-cells are found mainly in what region of lymph nodes

the paracortex, region of the cortex closest to the medulla

37

follicles of lymph nodes are the site of

antigen presentation and B cell differentiation
-follicles (germinal center) contain immature B cells, mature lymphocytes, and follicular dendritic cells (don't have to identify these tho)

38

microanatomy of secondary (activated follicle

- contains the germinal center, which is subdivided into basila dark zone (DZ) and apical light zone (LZ)
-both are contained in the marginal zone
-marginal zone contains lots of lymphocytes

39

paracortex contains mainly

-T cells, macrophages, and high endothelial blood vessels

40

lymphocytes enter lymph nodes via...

peripheral blood

41

dendritic cells enter lymph nodes via...

afferent lymphatics

42

spleen function

-filters blood; old/senescent rbc and wbc
-recovers and stores iron
-macrophages of red pulp commonly contain portions of RBC and hemosiderin
-samples/removes antigens from blood
-mounts immune responses against blood-borne antigens
-hematopoiesis in fetus
-stores platelets and RBC

43

spleen storage function

-stores RBC and platelets
-mainly occurs in horse, dog, and cattle
-smooth muscle is a prominent feature of capsule and trabeculae in species
-splenic contraction increases systemic hematocrit
-cats do not have a storage type spleen

44

splenic structure

-outer capsule is dense connective tissue with underlying smooth muscle
-capsule give rise to trabeculae: collagen, elastic fivers, smooth muscle
-each trabeculae contains a central artery or vein

45

splenic white pulp

-has central arterioles
-periarterial lympoid sheaths/PALS (thymus derived)
-and follicles (bone marrow derived)
-has lymphocytes, site of immune response

46

splenic red pulp

-has sinusoids for RBC storage
-parenchyma composed of macrophages and blood cells eventually enter venous sinuses

47

how are porcine lymph nodes different from other animals

-they are 'opposite': afferent vessels enter hilus, follow trabeculae, and exit via efferent vessels
-as opposed to other animals, where the efferent vessels exit through hilus

48

splenic blood flow

-enter via central artery
-branches to form penicillary arteries
-end in sheated capillaries (no endothelial cells, end blindly)
-blood enters space in parenchyma
-then to sinus system
-sinuses become larger and larger
-then splenic vein
-hepatic portal vein
-called open circ system system parenchyma not a true blood vessel

49

splenic venous sinuses

-post-parenchyma
-compose the rest of red pulp
-have long contractile endothelial cells
-basement membrane is discontinuous

50

white pulp parenchyma, what structures do B cells and T cells form?

-B cells: form lymphoid follicles, have germinal centers in young animals
-T cells: located around central arterioles, forming the periarteriolar lymphoid sheath

51

Mucosal Associtaed Lymphoid Tissue name the types

-gut-associated lymphoid tissue
-bronchial-associated lymphoid tissue
-tonsils
-ocular
-urogenital
-mammary

52

secondary lymphatic tissues functions

-strategic locations at sites of antigen entry
-antigen presenting cells induce immune response
-single or aggregations of lymphoid nodules
-augment mechanical and chemical barriers of surface mucosal epithelium

53

gut-associated lymphatic tissue (GALT) includes:

-solitary and aggregated lymphatic nodules
-intraepithelial lymphocytes
-subepithelial lymphocytes
-plasma cells
-macrophages

54

aggregated lymphatic nodules/peyer's patches of GALT

-present in small intestine's ileum
-may involute with age, may function different to smaller patches]
-smaller aggregated nodules in small intestine, colon, and rectum persist into adulthood

55

lacteals

-blind-ended lymph capillaries in small intestinal villi
-micelles from the chyme are absorbed, converted by the cell to chylomicrons; these enter lacteals to become part of the chyle
-smooth muscles of villi contract, pumping the lacteal to force chyle into lymphatic vessels

56

aggregated lymphatic nodules/peyer's patches cont.

-found in lamina propria and submucosa of distal ileum
-B cells migrate there from bone marrow
-because some level of B cell maturation occurs here, often considered as a primary lymphatic organ
-same central light and peripheral dark zones
as other lymph nodules
-overlain by simple columnar (M-cells)
-bursa of fabricius in chickens considered its equivalent

57

M-cells

-microfold cells, the simple columnar layer covering peyer's patch domes
-specialized epithelial cells
-pinocytose GI contents and secrete them on lymphocytes and macrophages of peyer's patches

58

Bronchiolar associated lymphoid tissue/BALT

-similar to GALT, found at bronchioles

59

Tonsils

-aggregated lymphatic nodules in pharynx
-adjacent to lumen of host organ, they sample luminal content
-have no afferent lymphatic vessels
-have local production of antibodies; are important in immune response
-may or may not have crypts

60

osmotic pressure and hydrostatic pressure: which increases and which decreases along the capillaries as lymph drains

-hydrostatic pressure decreases as lymph/blood drains from the capillaries
-osmotic pressure increases

61

lymphatic vessels:

blind-ended tubes lined by endothelial cells
-absorb fluid from interstitium, pass it back into blood stream
-inflammatory cell and antigen movement from peripheral tissue to nearest local lymph node for recognition in response

62

lymphatic vessel appearance

-possess valve
-clear content, no erythrocytes, occasionally lymphocytes

63

lymphatic vessel flow

-deliver lymph to lymph nodes (which are regional monitoring centers for immune response)
-lymph flows in one direction from periphery to heart
-surrounding tissues compress or expand on vessel
-one way valve prevents backflow