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Microanatomy 2 > Lymphoid System > Flashcards

Lymphoid System Flashcards

1
Q

The Immune system

A

Provides protection for the body against invading pathogens
- initial protection of body provided by epithelium that covers all surfaces
- Immune system takes over protection once epithelial barrier is breached

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2
Q

Types of immune system

A

Innate( natural) immune system
Adaptive (acquired) immune system

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3
Q

Innate(natural) immune system

A

nonspecific, performed by complements, macrophages, neutrophils, and natural killer cells

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4
Q

Adaptive (acquired) immune system

A

Reacts against specific antigenic component, performed by lymphoid system

Two types: Humoral immunity
Cellular (cell mediated) immunity

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5
Q

Lymphoid tissue

A

Specialized form of connective tissue that involved in adaptive immune defense of body

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6
Q

Lymphocyte

A

Principal functional cell
Mature and immature forms
( lymphoblasts, medium and small lymphocytes)

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7
Q

Humoral Immunity

A

Antigen stimulates production of an antibody ) from B-lymphocytes: plasma cell) which neutralizes antigen

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8
Q

Cellular (cell mediated) Immunity

A

Cell(t-lymphocytes) directly attacks foreign cell or altered host cell through binding to the specific antigen or “epitope”

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9
Q

Types of Lymphocytes

A

B lymphocyte
T lymphocyte
Null cell
Indistinguishable when viewed under the light microscope

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10
Q

B Lymphocytes

A

Surface antibodies (IgD & IgE) act as receptors
Effector cell
- Plasma cell –> production of antibodies
Memory cell
- Programmed to react to specific antigen

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11
Q

Antigen

A

Molecule(s) that is (are) foreign to the body

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12
Q

Antibody (immunoglobulin)

A

Protein secrete to neutralize an antigen
Key component of a humoral immune response to an antigen

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13
Q

T Lymphocytes

A

Surface receptors bind with antigens
Effector cell
- Destroy foreign cells and altered cells by enzymes and cytokines
Memory cell
- Programmed to react to specific antigen

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14
Q

Null Cells

A

Small portion of lymphocytes
NK cells (natural killer cells)
- Destroy foreign, viral, altered, or cancer cells without help of t lymphocytes or passage through thymus

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15
Q

Stem Cells

A

Cell of origin for cells of blood

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16
Q

Dendritic cells

A

Antigen presenting cell

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17
Q

Other cell types

A

Macrophages
Granulocytes

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18
Q

Reticular Connective tissue

A

Framework of lymphoid tissue
Reticular cells

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19
Q

Reticular Cells

A

A “fibroblast”with specialized function to produce and maintain reticular connective tissue

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20
Q

Arrangements of lymphoid tissue

A

Diffuse lymphoid tissue (T-cell zone)
Dense solitary lymph nodules (B-cell zone)

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21
Q

Mucosa-Associated Lymphoid Tissue (MALT)

A

Non-encapsulated lymphoid tissue located in the mucosa
Examples: Gut and bronchus associated ( GALT and BALT)

22
Q

Lymphoid organs

A

Highly organized lymphoid tissue Capsule with trabeculae or septa (connective tissue)

Have both diffused lymphoid tissue and nodules (except in thymus)

23
Q

Primary Lymphoid organs

A

Sites where lymphocytes produced &/ or become immunocompetent
Organs include bone marrow and thymus

24
Q

Secondary Lymphoid organs

A

Site where “immunocompetent” lymphocytes contact antigens and proliferate
Organs include lymph nodes, Spleen, Tonsils, Peyer’s patches, Hemal Nodes

25
Q

Lymph Node

A

Secondary Lymphoid organ
Is palpable
Function: Regional filtration of tissue fluid (lymph)
- Antigen recognition
- Antibody production
- Lymphopoiesis

26
Q

Tissue Fluid of Lymph node

A

Fluid component of blood that leaves circulatory system to enter extracellular matrix of connective tissue
- Leaves extracellular matrix & re enters blood capillaries & venues

27
Q

Lymph

A

Is excess tissue fluid.
Enters lymphatic capillaries for returned to the general circulatory system

28
Q

Lymph Channels (pathway for tissue fluid through lymph node)

A

Afferent lymphatic vessels
Intranodal channels
- Subcapsular sinus
- Intermediate sinus
- Medullary sinus
Efferent lymphatic vessel

29
Q

Stroma

A

Capsule
- Dense irregular connective tissue
Trabeculae
- Internal struts
Reticular Connective Tissue
- Form intranodal sinuses
- Stellate reticular cells and squamous cells

30
Q

Parenchyma: Lymph node

A

Cortex
- Outer layer housing lymphoid nodules; B-lymphocytes

Parecortex
- Area between cortex and medulla, housing T-lymphocytes “thymus-dependent zone”

Medulla
- Center area composed of medullary cords and sinuses

31
Q

Primary nodule

A

Resting stage
congregation of B lymphocytes

32
Q

Naive B-lymphocytes

A

Immunocompetent but never interacted with an antigen

Coming from bone marrow, enter node from high endothelial venules (HEVs) of paracortical (thymic dependent) region

33
Q

Memory B lymphocytes

A

May enter through HEVs or afferent lymphatic vessels

34
Q

Secondary Nodule

A

Site of proliferation(mitosis) of B-lymphocytes following antigen binding

Forms a germinal center by activated lymphocytes

Outlined with corona

Germinal center is formed in a pre-existing primary nodule
- primary nodule activation to form germinal center, then become secondary nodule

35
Q

Germinal Center

A

Activated B-lymphocytes come to primary nodule & proliferate

Lymphoblast formed, and further divided to plasma cells and memory cells

Follicular dendritic cell assists with proliferation of lymphocyte, and present antigen to lymphocyte

36
Q

Corona (mantle)

A

Dense accumulation of lymphocytes surrounding germinal center

Composed of:
- Displaced naive & memory B-lymphocytes & T-lymphocytes from original primary nodule
- transient newly formed memory B-lymphocytes & plasma cell

37
Q

Paracortex

A
  • “Thymus dependent zone”
  • Diffuse lymphoid tissue
  • Localization of T-lymphocytes & interdigitating dendritic cells
    (antigen presenting cells)
  • Site of proliferation of T-lymphocytes
  • “high endothelial venules” vascular sites where lymphocytes leave the vascular beds and enter
    lymph node
38
Q

Medulla

A

Medullary cord
Lymph Sinuses

39
Q

Medullary Cord

A

Diffuse lymphoid tissue
* Congregation of plasmacells, lymphocytes &
macrophages

40
Q

Lymph Sinuses

A

Open channels formed by reticular tissue, filled with lymphocytes and lymph fluid

41
Q

Blood circulation in Lymph Nodes

A
  • Nodal artery enters node at hilus
    – Branches traverse medulla in trabeculae
    – Branches leave trabeculae to enter paracortex & cortex
    – Capillary bed formed in cortex
    – Capillaries merge to form High Endothelial Venules
    – Venules drains into larger veins, which exit at the hilus
42
Q

High Endothelial Venules

A

Located in PARACORTEX

Endothelial cells are cuboidal in shape

Receptors for recognition by lymphocytes (traveling in blood)

Lymphocytes leave blood & enter the paracortex and nodules

43
Q

Peyer’s Patch

A

Secondary lymphoid organ

Most abundant in wall of ileum

Aggregated Lymphoid Nodules

Diffuse lymphoid tissue between & around nodules

Lymphoid nodules located in submucosa

Diffuse lymphoid tissue extends into lamina propria

Classified as component of “Gut Associated Lymphoid Tissue”
(GALT)

no capsule

only efferent lymphatic vessels

44
Q

Peyer’s Patch: Aggregated lymphoid nodules

A

*Primary nodules
*Secondary nodules
*Germinal center
*Corona

45
Q

Peyer’s Patch: diffused lymphoid tissue

A

*Between & around nodules
*“High endothelial venules”
Site where B-lymphocytes & Tlymphocytes leave circulating
blood & enter Peyer’s patch

46
Q

Peyer’s Patch: B-lymphocytes

A

Proliferate in germinal center of secondary nodules

47
Q

Peyer’s Patch: T-lymphocytes

A

localized in satellite region adjacent to proximal portion of nodules

48
Q

Peyer’s Patch: M- cells (microfold cells)

A

*Specialized cells in simple columnar epithelium that lines luminal surface of ileum ABOVE PEYER’S PATCH

*Apical surface of M cell contacts lumen of ileum

*Sample (capture) antigens in lumen of ileum

*Antigen presenting cells embedded in basal surface of M cell

49
Q

Tonsil

A

*Incompletely encapsulated
*Multiple sites around nasal and oral body openings
*Secondary lymphoid organ
*Intercept antigens entering body orifices

50
Q

Tonsil : Stroma

A

Capsule

Microanatomy 2 (6 decks)

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