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Histology Test 3 > Spleen > Flashcards

Spleen Flashcards

1
Q

Largest lymphoid organ

A

Spleen

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2
Q

Spleen- Functions?

A
  1. BIGGEST source of macrophages
  2. filters blood
  3. Kills old RBC and recycles Fe.
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3
Q

Spleen Framework?

  1. Capsule
  2. meshwork?
  3. blood vessels course through….?
  4. Hilum characteristics?
A
  1. CT of mesothelium with trabeculae that extend into the interior and branch and anastomose= trabecula. Trabecula contain efferent lymphatic vessels. No afferent lymph vessels.
  2. Pulp (red and white) supported by reticular fiber meshwork (Just like lymph nodes)
  3. Blood vessels course through trabeculae.
  4. Hilus of of spleen is where blood vessels enter–capsule is heaviest here.
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4
Q

Divisions of Spleen

A
  1. White pulp= T-cells
  2. Red pulp= mostly macrophages. Splenic cords are made of red pulp. Splenic sinuses are the veins within red pulp. Reticular fibers and cells support the red pulp
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5
Q

Splenic sinus

A

vein that carries blood through the red pulp.

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6
Q

Efferent lymphatic vessels of spleen can be found in? Afferent?

A

Capsule, large trabeculae, and SOME in white pulp. NO AFFERENT LYMPHATIC VESSELS

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7
Q

Splenic cord

A

the actual “red pulp” stroma surrounding the splenic sinus. This is where filtering takes place and old RBC are eaten.

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8
Q
  1. Splenic nodules are made of ?
  2. Splenic nodule forms along ?
  3. [1] is surrounded by?
  4. Function of splenic nodule?
A
  1. White pulp
  2. central artery
  3. PALS- central a.(leaving trabeculae) ensheathed in lymphatic tissue (t-cells, mostly)
  4. detects antigens from blood with antigen presenting cells
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9
Q

White Pulp Periphery

A

Marginal zone with marginal sinuses. White pulp transitions to red pulp at the sinuses. This is where most of antigen detection takes place.

(spleen)

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10
Q

PALS

A

periarterial lymphatic sheath= lymphatic tissue covering blood vessels leaving the trabeculae–T CELLS MOSTLY

(Spleen)

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11
Q

Red pulp
1. Function
2. support
3.

A
  1. Filters blood, macrophages remove dead RBC (because it’s creepy if they aren’t dead..)= erythrophagia
  2. reticular fibers and cells
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12
Q

Antigens in spleen?

A

Enter via blood and and detected by antigen presenting cells in splenic nodules (esp marginal sinus)

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13
Q

central artery

A

arteries that leave trabeculae with a lymph sheath

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14
Q

Blood flow in splenic nodule

A

Central artery with a periarterial sheath (t-cells) branches from the arteries running in the trabeculae. When the central artery passes through a nodule, it branches into follicular/radial arteries that drain into marginal sinuses.

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15
Q

Blood flow in red pulp

A

after passing through the splenic nodule and into the red pulp, the central arteriole is NOT covered by PALS. It now gives off pencillar arterioles

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16
Q

Pencillar arterioles

A

Marginal sinuses lead to penicillar arterioles, which branch out “like a fan”
1st segment= pulp arteriole with smooth muscle sheath
2nd segment= has sheath of macrophages, reticular fibers and cells.
3rd segment= terminal capillary

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17
Q

periarterial lymphatic sheath VS sheath around 2nd segment of penicillary arterioles

A

PALS surround CENTRAL arterioles as they leave trabecula. Mostly T-cells

Sheath around 2nd part of penicillar arteries is short and made up of macrophages, mostly.

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18
Q

Terminal capillary in spleen

A

final segment of a penicillar arteriole (found in the red pulp).

  1. Closed circulation= drain into sinus which leads to red pulp veins->trabecular v.
  2. Open circulation= drains into red pulp =stroma of splenic cords
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19
Q

Recovering blood when it drains via open circulation?

A

Blood in splenic cords re-enters circulation by passing into sinusoids. This process allows platelets, leukocytes and flexible RBC through. Fat swollen ready to die RBC are blocked and undergo apoptosis and are eaten by macrophages.

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20
Q

formation of splenic nodule?

A

B-cells in PALS can be activated if they recognize and antigen in the blood–it traps the antigen. As the nodule grows around the activated B-cell, the central artery sends out branches (follicular/radial arterioles) to the small sinuses in the peripheral marginal sinus (has developing B-cells) —–his notes contradict the book. According to notes the detection usually takes place at the marginal sinus…..

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21
Q

Thymus

  1. Outside?
  2. divisions?
  3. Major cells?
A
  1. CT capsule that gives off trabeculae
  2. trabecula divide thymus into lobules. Lobules divided into medulla and cortex
  3. Epithelial reticular cells in both parts, but they have DIFFERENT functions in each part.
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22
Q

Lobule of thymus

A

Made of cortex (outer) and medulla (inner). Medulla of each nodule is continuous via AXIAL strand.

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23
Q

Axial strand

A

in thymus, this is what interconnects the medulla part of each lobule

24
Q

Trabeculae

A

Found in the thymus and spleen. The thymus has lobules due to trabeculae. In the spleen, the trabeculae carrie blood vessels. the spleen does NOT have lobules.

25
Q

Cortex of thymus

  1. function
  2. Cell types
A
  1. selection process of t-cells

2. t-cells, epithelial reticular cells (ectodermal), macrophages and large lymphocytes

26
Q

Medulla of the thymus

  1. function
  2. parts?
  3. Cells?
A
  1. Medullary ERCs makes hormones (thymosin and thymopoietin)
  2. ERC network and thymic corpuscles (hassal’s)
  3. Medullary ERC and mature t-cells that pass cortical ERC selection.
27
Q

Epithelial reticular cells (ERC)

  1. types
  2. they do no make?
A
  1. cortical=ectodermal and medullary= endodermal

2. DO NOT MAKE RETICULAR FIBERS!!!

28
Q

ERC- cortical Functions (x4)

A
  1. program which T-cells will die and which t-cells live on (to live in medulla) via POSITIVE and NEGATIVE selection. ERCs present t-cells with MHC I and II complex.
  2. part of blood-thymus barrier
  3. eCtodermal= cortical
  4. lining: separate cortex from capsule. Surround blood vessels in cortex.
29
Q
  1. T helper cells
  2. t-cytolytic cells?
  3. differentiation?
A
  1. T -helper= CD4+, CD8- ( you need more help watching a 4 year old than an 8 year old)
  2. T-cytolytic= CD8+ , CD4-
  3. Differentiation controlled by medullary ERCs
30
Q

ERC- medullary - functions?

A
  1. differentiation of t-helper and t-cytolytic cells
  2. source of hormones= thymosin and thymopoietin
  3. structure: make ERC netowrk and Hassal’s corpuscles
    4.
31
Q

Selection process of t-cell

  1. Part 1 -location and process
  2. Part 2 - location and process
  3. Final t-cells that aren’t eliminated can?
  4. What controls this?
A
  1. Cortex: Positive selection: T-cells are tested to see if they recognized MHC I (CD4+) and II (CD8+). [ this tests TCR]
  2. Cortico-medulalry jct: Negative selection:If they recognize self- antigen they are killed in cortico-medullary junction. If not they live on. They stop expressing CD4 or CD8 at this point to be either CD4+ OR CD8+.
  3. recognize self MHC (functional TCR) but not self-antigens.
32
Q

thymic lymphocyte life span

A

most die in 3-5 days (degenerate in thymus because they didnt pass the tests by cortical ERCs. If they pass, they enter blood via high endothelial post-cap venules

33
Q

High endothelial post-capillary venules

  1. previous lecture it was?
  2. in thymus?
  3. location in thymus?
  4. endothelium?
A
  1. This is how most lymphocytes enter lymph nodes (previous lecture)
  2. how thymic lymphocytes enter the circulating pool
  3. cortico-medullary junction
  4. “thickened, similar to one in lymph node” (tall cuboidal epithelial cells)
34
Q

Cortico-medullary junction

A

common place for the elimination of lymphocytes (after failing negative selection) by macrophages and dendritic cells.

35
Q

Hassal’s corpuscle

A

ERC in medulla form the thymic corpuscle

36
Q

Blood supply to thymus

A

Arteries enter along medullary core and distribute to cortex. NON FENESTRATED epithelium, thick basement membrane and sheath of ERCs (tight junctions) . IMMUNOLOGICALLY SEQUESTERED!
you don’t want maturing t-cells to be exposed to blood antigens

37
Q

TCR extra info for big pic

A

T-cell receptor
Found on t-cells
recognizes antigens bound to self-MHC molecules. In positive selection, t-cell needs to recognize self-MHC= checking integrity of TCR.

38
Q

Review: MHC I vs MHCII

A

MHC I= recognized by CD8+ lymphocytes

MHC II= recognition by CD4+ lymphocytes

39
Q

CD4 + vs CD 8+

A

Initially lymphocytes have both. ERCs in medulla sesct for the loss of one. CD4+ lymphocytes become t helper cells.
CD8+ become cytotoxic lymphocytes
After differentiation in medulla (at corticomedullary jct) the lymphocytes exit via high endothelial capillary venules and enter blood circulation

40
Q

Thymus- Lymphatics in it?

A
  • No lymph nodules

- Interlobular CT has efferent vessels that DRAINS thymus. No afferent lymphatics or sinuses

41
Q

thymus at puberty

A

starts to deteriorate. Still functional

42
Q

Do T-helper cells and T-cytolytic cells differentiate more?

A

Yes, after leaving thymus and circulating in blood, they can interact with antigen presenting dendritic cell. This usually happens in lymphoid organs.

43
Q

Sickle cell and spherocytes?

  1. What happens in spleen?
  2. Symtpoms?
A
  1. Get trapped in splenic sinuses and are destroyed by macrophages.
  2. Anemia, hyperbilirubinemia, splenomegaly (from blockage)
44
Q

Splenomegaly

A

Can be due to blockage (sickle cells, spherocytes) or portal hypertension (from cirrhosis of the liver)

45
Q

DiGeorge syndrome

A

Inherited immunodeficiency–no cortical epithelial reticular cells. No t-cell development.

46
Q

Liver cirrhosis can cause?

A

Portal hypertension–> splenomegaly

47
Q

Thymocyte (t-cell) maturation

give location and characteristics

A
  1. Subcortical thymocyte- double negative for t-cell receptors CD4 and CD8
  2. Cortical t-cell- makes TCR so double positive= CD8 +, CD4+
  3. Medullary thymocyte-single positive t-cell with CD4 or CD8 (selective loss of CD4 or CD8)

(his pic shows TCR being added in medulla…..book shows TCR positive, CD4, CD8+ all happening in cortex)..FYI

48
Q

CD4: CD8 ratio?

A

can be indicative of diseases?

High CD8: CD4 ratio occurs in AIDs patients.

49
Q

Review:

Types of T-helper cells?

A

T-helper cells recognize MHC II = CD 8+.
Th1= viral and bacterial infections
Th2= parasitic infections

50
Q

MALT?

A

mucous-associated lymphoid tissues. This is diffuse immune cells in digestive, respiratory, or urogenital mucosa.
Ex: peyer’s patches, tonsils,

51
Q

Location where lymphocytes are

  1. formed initially
  2. activation and proliferation
A
  1. primary lymphoid organs= thymus and bonemarroy

2. secondary= lymph nodes, spleen, MALT

52
Q

Major lymph organs with cortex and medulla

A

Thymus and lymph nodes

53
Q

Lymph nodules can be found in?

A

MALT (ex: peyer’s patches), cortex of lymph nodes, white pulp of spleen

54
Q

Afferent lymphatic vessels are NOT found in?

A

Thymus, MALT, or spleen

55
Q

lymphoid organ with afferent lymphoid vessels?

A

Lymph nodes–afferents are at the capsule and empty into the subcapsular sinus

56
Q

lymphoid organs with efferent lymphoid vessels?

A 
All
Thymus- few in septa
MALT- yes 
Lymph- at hilum
Spleen- in trabeculae
57
Q

Special features of each type of lymphoid organ

  1. Thymus
  2. MALT
  3. Lymph nodes
  4. Spleen
A
  1. Hassal’s corpuscle in medulla. ERCs in both parts
  2. M-cells cover peyer’s patches; crypts in tonsils have submucosal lining
  3. HEV, medullary cords medullary sinuses
  4. white and red pulp

Histology Test 3 (8 decks)

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