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FoundSci Unit 6 > Lymph Tissues and Organs > Flashcards

Lymph Tissues and Organs Flashcards

1
Q

What are the 3 main lines of defense of the immune system?

A

Protective surfaces

Innate immune system

Adaptive immune system

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2
Q

How does the immune system use protective surfaces?

A

First line of defense

Physical barrier

Keep out pathogens as long as they stay intact

Breaches in skin or mucosal linings allow pathogens into deeper tissues

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3
Q

What is the innate immune system?

A

Rapid reactions to infection, but cannot learn

Cells - neutrophils, eosiniophils, basophils, mast cells, macrophages, natural killer cells

Cells equipped with generic protein tools to fight pathogens - bacteriocidal enzymes for example

Cells able to mobilize rapidly

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4
Q

What is the adaptive immune system?

A

Slow to respond to infections, but able to learn

Second and subsequent encounters with pathogens elicit greater, more specific and faster responses

Takes 3-5 days to mount a response - needs large number of lymphocytes with specificity for a particular pathogen (or antigen)

Main cells - B lymphocytes (b cells) and T lymphocytes (T cells)

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5
Q

What are B lymphocytes?

A

Humoral response - cells use antibodies to recognize antigens

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6
Q

What are T lymphocytes?

A

Cellular response - cells recognize antigens directly

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7
Q

Parenchyma

A

Parts of a gland or organ that are specialized for that gland or organ’s unique function - differs depending on structure

Ex. Lung parenchyma - airways and alveoli

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8
Q

Stroma

A

Support tissue - usually CT proper

Any CT that covers, subdivides, and or physically supports functional cells in parenchyma

Usually has vessels and nerves that supply parenchyma in generic way

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9
Q

What is the main site of inflammatory and immune response in tissues?

A

CT of the stroma

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10
Q

What is the lymphoid system?

A

All places where lymphoid cells proliferate, differentiate, and mature into immunocompetent cells, or where they mount immune responses

Lymphoid cells - B and T cells

Lymphatic tissues can form temporarily within other tissues or organs and can also form permanent structure (=lympoid organs)

Lymphoid organs

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11
Q

What are lymphoid organs?

A

Bone marrow

Thymus

Lymph nodes

Spleen

Various types of mucosa-associated lymphoid tissue

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12
Q

What are primarily (central) lymphoid organs?

A

Organs where lymphocytes differentiate, become educated and learn to distinguish self from not self

Bone marrow and thymus

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13
Q

What are secondary (peripheral) lymphoid organs?

A

Organs and tissues where mature B cells and T cells encounter foreign antigens/pathogens, become activated in response to antigens, and where immune responses take place

Lymph nodes, spleen, and MALT tissues with nodules

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14
Q

What do we also classify lymphoid tissues based on, beside organs?

A

Organization - diffuse vs. nodular

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15
Q

Where do lymphocytes differentiate, develop, and mature to become B lymphocytes (B cells)?

A

Bone marrow

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16
Q

How does bone marrow function as a primary lymphoid organ?

A

Bone marrow releases mature (unactivated) B cells into blood and they travel to secondary lymphatic organs that have nodules.

B cells in secondary organs are activated when an antigen binds a surface immunoglobulin and then it undergoes mitosis to form clones

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17
Q

What can clones do when a B cell is activated?

A

Clones can synthesize an Ig with same antigen specificity

Most clones mature into plasma cells

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18
Q

What do plasma cells make?

A

lots and lots of antibody (Ig)

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19
Q

What does the thymus do as a primary lymphoid organ?

A

Precuror of T cells start out in bone marrow and go to thymus

Differentiate into thymus into immunincompetent T cells - thymocytes

Thymocytes mature into immunocompenetent lymphocytes in thymus

Mature in thymus and called T lymphocytes (T cells)

Thymus released T cells (unactivated) into blood and they travel to 2 thymus dependent secondary lymphatic tissues (paracortex of lymph nodes and PALS of spleen)

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20
Q

Where do T cells going after being released from thymus?

A

Thymus dependent secondary lymphatic tissues

Paracortex of lymph nodes

PALS of spleen

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21
Q

What is MALT?

A

Mucosa Associated Lymphoid Tissue

Any lymphoid tissue located within a mucous membrane lining a tract

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22
Q

Where is mucosa located and what is the benefit of MALT?

A

Walls of respiratory tract, GI, and GU tracts

Prominent near orifices, major transitions within tracts and near where trachea splits into primary bronchi

Antigens or pathogens get through epithelial lining of a tract are immediately confronted by immunocompetent lymphocytes in tissues below

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23
Q

What is GALT?

A

Gut Associated lymphoid tissue

24
Q

What is BALT?

A

bronchus associated lymphoid tissue

25
What are tonsils considered?
MALT embedded in walls of pharynx/throat
26
What is diffuse lymphatic tissue? What is its structure?
Least organized lymphatic tissue Always forms within some other organ Unorganized clusters of lymphocytes - never forms lymphatic nodules (follicles), temporary aggregations Cells: B cells, T cells, plasma cells, monocytes/macrophages Stroma: No capulse, reticular CT may be present to suspend and support cells
27
What are solitary lymphatic nodules?
Isolated temporary structures and can appear, disappear, and reappear
28
What are lymphatic aggregates?
Permanent clusters of lymphatic nodules within another organ
29
What are secondary lymphatic nodules collectively called and what do they contain?
Peyer patches Permanent structures in walls of ileum Contain B cells, T cells, and macrophages Similar aggregates in walls of appendix
30
What are the 3 kinds of tonsils?
Palatine tonsils Lingual tonsils Pharyngeal tonsils
31
What are the characteristics of tonsils?
All 3 types are MALT and contain lymphatic aggregates Stroma: surfaces covered with epithelium and partial/incomplete CT capsules with long septa. Capsules physically protect underlying tissue and may provide some protection vs spread of tonsillar infections Cells: B cells and T cells
32
What do lymph nodes do?
Filter lymph - remove bacteria and other antigens or pathogens
33
Afferent lymphatic vessles
Where lymph arrives (on convex side of node)
34
Hilum of lymph node
Area with blood vessels and efferent lymphatic vessels (on concave side of node) Lymph exits node via efferent lymphatic vessels
35
What are lymphatic nodules?
Dense spherical aggregations of lymphocytes with some organization Sites of initial immune responses 2 types - primary and secondary Can be solitary or form aggregates Always present in the tonsils, lymph nodes, and spleen
36
What is the mantle zone and germinal center of secondary lymphatic nodules?
Mantle zone - smaller but mature lymphoctyes Germinal center - most are activated B cells (many dividing to form new clones), some follicular dendritic cells (antigen presenting cell) Germinal center site where lymphocyte clones are produced - mitotic figures
37
What are palatine tonsils?
Located at boundary of oral cavity and oropharynx Covered with nonkeratinized stratified squamous epithelium Have deep crevices called tonsillar crypts (fissures)
38
What are lingual tonsils?
Small bumps on the dorsal surface of posterior 1/3 of tongue Covered with nonkeratinized stratified squamous epithelium Have crypts
39
What are pharyngeal tonsil?
Located in roof of nasopharynx Covered with ciliated pseudostratified columnar epithelium Has pleats (no crypts) = broader folds of surface
40
What types of cells are in lymph nodes?
B cells T cells Plasma cellss Stellate reticular cells - synthesize and secrete collagen III fibers and ground substance for ECM Dendritic cells - antigen-presenting cells and monitor stroma for foreign substances Macrophages - phagocytic cells, line sinuses, antigen presenting cells
41
What is in the paracortex and what does it do?
High endothelial venules - special postcapillary venules lined by cuboidal endothelial cells, instead of the ormal simple squamous endothelial cells Specialized venules that allow B and T cells to pass through their walls and enter lymph node tissue faster/more easily
42
How do lymphocytes enter lymph nodes?
Enter lymph nodes from the bloodstream via HEVs in the paracortex Most lymphocytes leave lymph nodes via efferent lymphatic vessels
43
What is the flow of lymph?
Afferent lymphatic vessels Subscapular sinuses Peritrabecular sinuses Medullary sinuses Efferent lymphatic vessel
44
What is the function and structure of thymus?
Primary lymphoid organ - site where T cells mature and become immunocompetent Stroma: capsule surrounds both lobes, trabeculae partially subdivide thymus into thymic lobules, thymus lacks afferent lymphatic vessels Parenchyma: medulla and cortex
45
What are the 3 types of cells in thymic cortex?
1. Thymocytes 2. Macrophages 3. Epithelial reticular cells (Types I, II, and III)
46
What are thymocytes?
Immature T lymphocytes
47
What are the function of macrophages in the cortex?
Phagocytize any developing T cells that do not meet thymic requirements
48
What is the function of epithelial reticular cells (Types I, II, and III)?
Form a 3D cellular framework that seals off the cortex and physically supports the thymocytes Some are also "teachers" that present self-antigens and foreign antigens to thymocytes
49
What are the cells in the thymic medulla?
Epithelial reticular cells (Types IV, V, VI) - seal off boundaries and form the 3D cellular framework that supports the developing T cells Thymocytes Some macrophages mature T cells
50
What do epithelial reticular cells?
Cortex: Types I, II, II - all 3 types work to create a pristine environment for the maturing thymocytes Medulla: Types IV, V, VI
51
What is is the blood-thymus barrier?
Ensures blood borne antigens do not get into cortical tissues where thymocytes are developing Isolates developing thymocytes and protects them from unregulated or premature exposure to antigens circulating in blood Creates an immunologically protected region within the thymic cortex Increased permeability of the blood-thymic barrier or premature exposure of thymocytes to antigens results in impaired immunity
52
What are the immune functions of the spleen?
Site of B cell and T cell proliferation Site where dendritic cells and macrophages present antigens Formation of antibodies that bind to antigens circulating in the blood Site where antigens are removed from blood
53
What are the hematopoietic functions of the spleen?
Filters cellular components of blood Inspects RBCs - removes old/damaged RBCs from circulation Recycles iron from destroyed RBCs Removed old/damaged platelets from circulation Hematopoiesis site
54
What is the white pulp of the spleen?
Splenic nodules - lymphatic nodules that lie along the paths of central arteries, most cells are B cells Periarterial lymphatic sheath - sheath of T cells around the central artery
55
What is the red pulp of the spleen?
Splenic cords (cords of Billroth) - branching cords of splenic tissue and splenic macrophages monitor RBCs remove old and damaged RBCs from circulation Splenic sinuses - blood filled sinusoidal capillaries

FoundSci Unit 6 (14 decks)

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