Hist: Lymphoid Tissue

Front 1

What are primary lymphoid tissues and what do they do?

Back 1

Bone marrow; thymus.

They make the cells that seed 2ndary lymphoid tissue.

NOT directly involved in immune response.

Front 2

What are secondary lymphoid tissues and what do they do?

Back 2

Mucosa-associated lymphoid tissue (MALT); Lymph glands; tonsils; spleen. They filter body fluids and respond by producing antibodies and cells, which neutralize/inactivate foreign material.

Front 3

Where will the inflammatory response start after a microbe penetrates an epithelium?

Back 3

In the CT layer (dermis or lamina propria)

Front 4

In what layer is diffuse lymphoid tissue located?

Back 4

Lamina propria

Front 5

What types of cells are in diffuse lymphoid tissue?

Back 5

Mainly lymphocytes, but also macrophages and plasma cells

Front 6

What happens to an antigen not inactivated by MALT?

Back 6

It travels thru lymph vessels to the lymph nodes.

Front 7

What is the combination of tissue fluid, antigens, and lymphocytes in lymph vessels called?

Back 7

Lymph.

Front 8

What filters the blood?

Back 8

Spleen

Front 9

Which cell possesses a multilobed nucleus, serve as first line of defense, and migrate to sites of infection from blood?

Back 9

Neutrophils (polymorphonuclear leukocytes, PMNs)

Front 10

What cell produces histamine and heparin in response to an antigen (allergy response)?

Back 10

Mast cells

Front 11

What cell releases factors that attract neutrophils and eosinophils?

Back 11

Mast cells

Front 12

How to ID mast cells?

Back 12

Centrally located nucleus and multiple large secretory granules.

Front 13

How to ID macrophages?

Back 13

Peripheral heterochromatin in the nucleus; frequently has a notch or indentation; has cellular projections

Front 14

What happens (briefly) in B Cell activation?

Back 14

Exposure to antigen and costimulation by a helper T lymphocyte

Front 15

What type of CT forms the stroma for lymphoid nodules, lymph nodes, spleen, and bone marrow?

Back 15

Reticular fibers (made of Type III collagen) and the reticular cells that produce them. Macrophages and other cells are positioned along the fibers to react if necessary

Front 16

Where can diffuse lymphoid tissue be located?

Back 16

In lamina propria, paracortex of lymph node, and white pulp of the spleen

Front 17

What is difference between diffuse lymphoid tissue and lymphoid nodule?

Back 17

Lymphoid nodule is more organized than diffuse lymphoid tissue, which doesn't form spherical structures. They both are made up primarily of lymphocytes, but the lymphocytes are less concentrated in the diffuse tissue.

Front 18

What is the difference between a primary and secondary lymphoid nodule?

Back 18

A primary lymphoid nodule is a <b>solid, spherical mass of lymphocytes </b> whereas a secondary lymphoid nodule contains a <b>paler patch in middle called germinal center.</b>

Front 19

What is a germinal center?

Back 19

A pale staining part in the middle of secondary lymphoid nodule.

Front 20

What are primary nodules seeded by?

Back 20

B lymphocytes, therefore they're called B-dependent areas

Front 21

What are the components of a secondary lymphoid nodule?

Back 21

Outer mantle/corona: B lymphocytes
Germinal center: Immunoresponsive B cells are formed and migrate to mantle

Front 22

What must happen for a primary nodule to become secondary?

Back 22

Must be stimulated by antigen

Front 23

What are macrophages doing in the germinal center of secondary lymphoid nodule?

Back 23

Phagocytosing degenerating lymphocytes

Front 24

What are peyer's patches? Where are they most commonly found?

Back 24

Aggregations of lymphoid nodules, most commonly found in ileum. They contain clusters of secondary nodules surrounded by diffuse lymphoid tissue.

Front 25

What forms a ring of lymphoid tissue in lamina propria of oral and nasal pharynges?

Back 25

Tonsils

Front 26

What is Waldeyer's ring?

Back 26

Lymph nodes, tonsils, and adenoids

Front 27

What were B cells originally named for?

Back 27

Bursa of Fabricius

Front 28

What organ is primarily responsible for setting up cell-mediated immunity?

Back 28

Thymus

Front 29

What organ is primarily responsible for setting up humoral immunity?

Back 29

Bone marrow

Front 30

What percentage of WBCs are lymphocytes?

Back 30

20-50%

Front 31

What are the 3 (main) types of T cells?

Back 31

Helper, Killer, memory

Front 32

What do helper T cells do?

Back 32

Stimulate the differentiation of B cells into plasma cells. (This is the one that's killed by HIV)

Front 33

What do killer T cells do?

Back 33

Kill foreign cells directly by disrupting their membrane

Front 34

What do memory T cells do?

Back 34

Act quickly to stimulate production of killer T cells when antigen is reintroduced

Front 35

What are immunoblasts?

Back 35

Very large basophilic cells that form T or B cells when they are stimulated by exposure to antigen

Front 36

What are antigen-presenting cells (examples?)

Back 36

Trap, process, and present antigen to lymphocytes resulting in lymphocyte activation.

Belong to monocyte-phagocyte system.

Includes macrophages, dendritic cells, Langerhan's cells, epithelial thymus cells.

Front 37

When does the thymus reach its
a) largest absolute size?
b) largest relative size?

Back 37

a) Puberty
b) Birth

Front 38

How is the thymus <b>stroma</b> embryologically derived?

Back 38

It's a bilobed organ, and its stroma is from epithelium of <b>endodermal origin</b> lining portions of 3rd pharyngeal pouch.

We'd expect it to be from mesoderm, but it's not.

Front 39

What seeds the thymus stroma during embryological development and what's it derived from?

Back 39

Hemopoietic stem cells, mesodermally derived from yolk sac, fetal liver, and bone marrow.

Thymoctyes develop once it's seeded.

Front 40

What are thymocytes and where do they come from?

Back 40

They're lymphocytes of the thymus. They develop from Hemopoietic stem cells (HSCs) originally from yolk sac, fetal liver, and bone marrow. THROUGHOUT LIFE they're supplied to the thymus from the bone marrow since they don't have a self-renewing ability.

Front 41

Where do we first encounter bacteria?

Back 41

MALT

Front 42

What are high endothelial venules (HEVs) and how are they associated with diffuse lymphatic tissue?

Back 42

They have tall <b>cuboidal endothelium </b>(instead of usual simple squamous).

They allow lymphocytes to enter the lymphatic region from the vessel.

They're frequently found together.

Front 43

What is the appendix very similar to? How is it different from this thing?

Back 43

Same morphology as Peyer's patches, but smaller lumen and very active large lymphoid nodules.

Front 44

What allows lymphocytes to escape from blood into lymphatic region?

Back 44

High endothelial venules

Front 45

What partially subdivides the lymphatic tissue in tonsils?

Back 45

Epithelial crypts

Front 46

What can a white patch on a palatine tonsil be?

Back 46

WBCs forming in lymphoid nodules

Front 47

What fluid are MALTs filtering? *******VERY IMPT*******

Back 47

Tissue fluid!

Front 48

What type of epithelium is on pharyngeal tonsil?

Back 48

Pseudostratified ciliated columnar epithelium

Front 49

What separates lymphoid nodules of palatine tonsil from underlying CT, dividing tonsil into lobules?

Back 49

A Capsule of Dense CT

Front 50

What are tonsils part of?

Back 50

MALT

Front 51

What are lymphatic vessels usually filled with in H&E staining?

Back 51

Pink-staining lymph fluid. NO RBCs

Front 52

Thymus is divided into __________ by a capsule

Back 52

lobules

Front 53

Each of the lobules has a darker-staining ________ and lighter-staining ___________

Back 53

Cortex; medulla

Front 54

The thymic stroma is derived from an _________ rather than CT. What implications does this have?

Back 54

Epithelium. No fibers are present and only a meshwork of epithelial reticular cells constitutes the framework/stroma.

Front 55

What cells are diagnostic for thymus, formed from a type of epithelial reticular cell?

Back 55

Hassall's corpuscles

Front 56

What is thymic medulla made of?

Back 56

mature T cells (made in cortex) that then enter the blood stream from the medulla

Front 57

What is thymic cortex made of?

Back 57

Mostly developing T cells (thymocytes) that are derived from blood stem cells that migrate from bone marrow

Front 58

Development of T cells

Back 58

1) Stem cells in bone marrow
2) These migrate to thymic cortex and are called thymocytes
3) Thymocytes develop into T cells and migrate to thymic medulla
4) From thymic medulla T cells enter bloodstream

Front 59

How do lymphoblasts differ histologically from T cells?

Back 59

They've larger, spherical nuclei. T cells nuclei are more heterochromatic.

Front 60

What do Hassall's corpuscles look like histologically? What do they contain?

Back 60

Concentrically arranged epithelial reticular cells. Contain keratohyalin granules.

Very large euchromatic nuclei

Front 61

What is the blood-thymus barrier made of?

Back 61

It's in the thymic cortex. It consists of epithelial reticular cells, endothelial cells, and basal laminae associated with these epithelia.

Front 62

T/F Valves in veins are more numerous than in lymph vessels

Back 62

FALSE.

Front 63

All lymph returns to vascular (blood) system via ________ on L side and _______ on R side at the junction of subclavian and internal jugular veins

Back 63

Thoracic duct; Lymphatic duct

Front 64

Lymph node is surrounded by dense CT capsule that sends ________ into the node

Back 64

Trabeculae

Front 65

What provides stroma for lymph node?

Back 65

Reticular CT

Front 66

What is the indentation in lymph node where arterial blood enters and venous blood and efferent lymph vessels leaves?

Back 66

Hilum

Front 67

What are the subdivisions of the lymph node cortex?

Back 67

Outer - containing lymphoid nodules populated mostly by B lymphocytes

Inner - (aka paracortex) contains mostly T lymphocytes, resembles diffuse lymphoid tissue

Front 68

What are the parts of the lymph node medulla?

Back 68

Medullary cords (finger-like projections); Medullary sinuses that receive lymph from cortical sinuses

Front 69

Where do afferent and efferent lymphatics enter and leave?

Back 69

Enter at subcapsular sinus, go thru cortex, leave at hilum thru medullary sinus

Front 70

The outer cortex and medullary cords of a lymph node are ____ dependent while the inner/paracortex is ______ dependent.

Back 70

B-cell; T cell

Front 71

Thru what vessel can a memory cell enter the lymph node stimulate germinal centers?

Back 71

HEVs

Front 72

Types of cells found in lymph node (4)

Back 72

1) Lymphocytes of all sizes
2) Plasma cells
3) Macrophages (dendritic or reticular)
4) Antigen-presenting cells

Front 73

99% of antigen carried by lymph is removed by __________ spanning sinuses of lymph nodes.

Back 73

Macrophages

Front 74

Tumor cells are perceived as ___________ to lymph nodes.

Back 74

antigen

Front 75

The spleen is subdivided into what? (2)

Back 75

White pulp, red pulp

Front 76

Arteries enter the spleen at the ______ and travel in ________ before supplying the parenchyma of the spleen.

Back 76

hilum; trabeculae

Front 77

What forms the interior splenic stroma?

Back 77

reticular CT

Front 78

What is PALS? (Periarterial lymphoid sheath)

Back 78

Diffuse tissue forming a sleeve around each arteriole.

Lymphoid nodules are suspended between these

Front 79

What fluid do each of these filter:
A) Spleen
B) MALT
C) Lymph node

Back 79

A) Blood
B) Tissue fluid
C) Lymph

Front 80

What's in the white pulp of spleen?

Back 80

PALS surround central (follicular) arterioles. T-dept. Like an arm covered with a shirt.

Germinal centers (B-dept)

Marginal zone at periphery of PALS.

Front 81

What's in the red pulp of spleen?

Back 81

Everything in parenchyma that isn't in white pulp.

Splenic/Billroth cords; venous sinusoids, arterioles, venules

Front 82

Why does red pulp appear red in fresh tissue?

Back 82

Because of large number of vascular sinuses

Front 83

What is the marginal zone?

Back 83

Junction of white with red pulp

Front 84

Splenic sinuses anastomose to form ___________ which enter the __________

Back 84

splenic veins; trabeculae

Front 85

The path by which blood enters splenic sinuses varies by species (closed or open). In humans, ________ is thought to predominate.

Back 85

OPEN. Blood percolates thru pulp before entering the sinuses.