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Lymphoid System Flashcards

(38 cards)

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1
Q

What are the functions of the lymphoid system?

A
  1. Phagocytosis
    -macrophages
  2. Production of immunological cells
    -APCs (dendritic, macrophage, B cells)
    -B & T lymphocytes
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2
Q

Describe primary lymphoid organs.

A

produce lymphocytes
1. Bone marrow = B cells mature
2. Cloacal bursa/bursa of fabricius (birds only) = B cells mature
3. Thymus = T cells mature
lymphocytes made in bone marrow mature in bone marrow, bursa, or thymus

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3
Q

Describe secondary lymphoid organs.

A

lymphocytes migrate to secondary lymphoid organs for activation & presentation of antigen
1. Lymph nodes (not in birds)
-filter antigens before returning it to blood
2. Spleen
-filters antigens from blood
3. MALT
-local immune response
4. Tonsils

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4
Q

What are the functions of primary lymphatic organs?

A
  1. Where T & B cells originate
  2. Access by antigen is controlled by barriers
  3. Apoptotic elimination of self reactive cells
  4. Released to circulation to sites where antigens are encountered (secondary lymphoid)
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5
Q

Describe bone marrow.

A

-source of pluripotent stem cells (B & T)
-stromal cells
>release factors that aid in cell differentiation
>macrophages

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6
Q

Describe the cloacal bursa.

A

‘Bursa of fabricus’
1. Dorsal wall of cloaca
2. Function is equivalent to bone marrow in mammals (B cell differentiation)

Pseudostratified columnar
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7
Q

Describe the thymus.

A
  1. Located in mediastinum (cranial to heart)
  2. Epithelial reticulum & lymphocytes
  3. Lymphocytic stem cells migrate from bone marrow
  4. Fill spaces between reticular epithelial cells
  5. Develop into T cells which migrate to secondary lymphoid organs & MALT
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8
Q

Describe the thymus cortex.

A
  1. Stains darker = high # of lymphocytes
  2. Positive selection
    -good developing lymphocytes (thymocytes)
  3. Tingible body macrophages near medulla
    -phagocytose dead bad T cells
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9
Q

Describe the thymus medulla.

A
  1. Epithelial reticular cells
  2. Negative selection
    -bad lymphocytes (auto reactive)
    -phagocytosed by tingible body macrophages
  3. Medullary reticular epithelial cells form thymic/hassalls corpuscles
    -lg central calcified/degen cells surrounded by concentric circles of keratinized cells
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10
Q

Canine thymus picture.

A

Cortex = darker
Medulla = lighter with Hassalls corpuscles (pink circles)

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11
Q

Canine thymus medulla picture.

A
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12
Q

Describe blood vessels in thymus.

A
  1. Arteries enter via corticomedullary junction within CT septa
  2. Divide into arterioles within septa
  3. Branch into capillary network in cortex ‘cortical capillaries’
  4. Cortical capillaries = blood thymus barrier
    -continuous endothelium
    -perivascular CT
    -sheath of epithelial reticular cell processes
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13
Q

Describe thymic involution.

A
  1. Thymus active in young animals & involutes after sexual maturity
  2. Gradual depletion of lymphocytes
  3. Replacement by adipocytes
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14
Q

Describe the lymph node.

A
  1. Capsule
    -dense, irregular CT
    -trabeculae
  2. Cortex
    -subcapsular sinus
    -lymphoid follicles (B cell rich)
    -paracortex (T cell rich)
    -high endothelial blood vessels
  3. Medulla
    -medullary cords
    -medullary sinus
  4. Stroma
    -reticular cells & fibers
Circles = lymphoid follicles. Medulla = white middle. Cortex = purple
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15
Q

Describe the flow of the lymph node.

A

Afferent lymphatic vessel -> subcapsular sinus -> cortical (trabecular) sinus -> medullary sinus -> efferent lymphatic vessel

CORTEX:
-lymphoid follicles & lymphocytes
MEDULLA:
-macrophages, lymphocytes, plasma cells

Ventral = efferent lymphatic vessel
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16
Q

Describe the cortex & medulla of the lymph node.

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A

Cortex:
-lymphoid follicles
-paracortex
-high endothelial blood vessels
Medulla:
-medullary cords
-lymphocytes
-macrophages
-plasma cells
>medullary sinus
—macrophages
—reticular cells

17
Q

Describe primary VS secondary lymphoid follicles.

Study These Flashcards
A

Primary -> ANTIGEN -> secondary

18
Q

Describe high endothelial venules (diapedesis).

Study These Flashcards
A

-in paracortex
-cuboidal
-allow extravasation of lymphocytes

19
Q

Medulla with sinus & cords (picture).

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A

S = sinus
C = cords

20
Q

Close up of sinus with macrophages.

21
Q

Labeled lymph node picture.

22
Q

Describe porcine lymph nodes.

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A

-backwards = central lymphoid follicles
-afferent lymphatics (V) enter though hilus (H) & follow trabeculae (t) to the central lymphatic nodules (n)
-peripheral sinus/cord (L)

23
Q

Describe hemal nodes.

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A

-alongside bloodstream
-in ruminants = dark colored
-erthryocytes in sinus
-no lymphatic supply
-near spleen, kidney, lg blood vessels (ventral side of vertebrae)
-function like the spleen

24
Q

Describe hemolymph nodes.

Study These Flashcards
A

-in pigs
-RBCs in sinus due to hemorrhage

1 = erythrocyte 2 = lymphocyte
25
What are the functions of the spleen?
1. Filter blood -old RBCs & WBCs -recover & store iron -macrophage of red pulp = contain RBCs & hemosiderin 2. Sample/remove antigen from blood via phagocytosis 3. Immune response against blood borne antigens (B & T) 4. Hematopoiesis in fetus 5. Store RBCs in horse, cat, dog -more smooth muscle & elastic in capsule = contraction & release of RBCs into blood -defense spleen = less smooth muscle in capsule (human & rabbit) -ruminants & pigs = intermediate
26
Describe the splenic structure.
-outer capsule = dense CT with smooth muscle & elastic fiber >gives rise to trabeculae = collagen, elastic fibers, smooth muscle >each trabecular contain central artery or vein
27
Describe white pulp VS red pulp.
WHITE -central arterioles -periarterial lymphoid sheath - PALS (T) -follicles (B) RED -venous sinus (RBCs) -reticular fiber & cells -macrophage, lymphocyte, plasma cells -PAMS
28
Describe splenic blood flow.
-via central artery & branches w periarterial lymphatic sheath (PALS) = white pulp -branches = penicillary arteries -end in blind ending capillaries w periarteriolar macrophage (PAMS) in red pulp -capillaries drain into red pulp parenchyma & then venous sinuses in an open circulation -capillaries drain into venous sinus = closed circulation -sinus well developed in dogs (cats, horse, ruminant = non sinusal spleen)
29
Describe MALT.
-GALT -BALT -tonsil -ocular -urogenital -mammary
30
BALT picture.
(Lymphoid tissue)
31
GALT picture.
*Light purple areas* -peyers patch -aggregated lymphatic nodules EX. Anti mesenteric side of ileum
32
Peyers patch picture.
33
Describe micro fold cells.
-peyers patch are covered by a columnar layer of micro fold cells (M cells) -specialized epithelial cells -pinocytose GI contents & secrete content on the lymphocytes & macrophages of peyers patch
34
Describe lacteals.
-blind ended lymph capillaries in small intestine villi
35
Describe lymphatic vessels.
-blind ended tubes -endothelial lining -absorb fluid from interstitum & pass it back to blood -inflammatory cell & antigen movement from peripheral tissue -lymph flow in one direction = from periphery to heart -surrounding tissue compress/expand vessel -one way valve = prevent backflow -anchoring fibrils = pull endothelial cells apart & fluid enters vessel
36
Picture of lymphatic vessel, arteriole, venule.
1. Left = lymphatic vessel with a valve -no erythrocytes 2. Middle = arteriole -1-3 layers of circular sm muscle 3. Right = venule -no sm muscle in wall
37
Describe function of lymphatics.
-deliver lymph to lymph nodes -drain tissue fluid through fenestrated capillaries
38
Describe palatine tonsil.
-collection of lymphatic nodules present in tunica muscle of pharynx -may/may not have crypts -no afferent lymphatics, samples lumen -efferent lymphatics drain tonsils -local antibody production

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