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Histology > Lymphoid II > Flashcards

Lymphoid II Flashcards

1
Q

Central Lymphoid Organs

A
  • Thymus (T cells) and Bone Marrow (B cells)
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2
Q

Encapsulated Peripheral Lymphoid Organs

A
  • Lymph Nodes - Filters Lymph

- Spleen- Filters Blood

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3
Q

Unencapsulated Peripheral Lymphoid Organs

A
  • MALT, single, diffuse, transitory, aggregated
  • Surveillance of antigens via mucosal surfaces
  • MALT houses 85% of all lymphoid tissues
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4
Q

Homing Pattern

A
  • B cells reside in the cortical nodules and medulla of the lymph nodes. As well as the lymphoid nodules in the spleen
  • T cells are in the paracortex of the lymph nodes anad Periarterial lymphatic sheath (PALS) of the Spleen
  • In the blood, mostly T cells
  • In mucosal Tissues- mostly B cells
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5
Q

Nodules vs Node

A
  • Nodules are not completely encapsulated
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6
Q

Circulating Lymphocytes

A
  • Mostly T cells

- small percentage of B cells and NK cells

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7
Q

Diffuse Lymphoid Tissue

A
  • small intestine
  • Lamina Propria- mainly B cells
  • Plasma cells secrete IgA
  • IgA protects- mucosal epithelium infection
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8
Q

Generation and Function of IgA

A
  • Produced by plasma cells
  • secretory piece/component added by epithelial cells, protects against lysosomal degradation
  • This component is clipped at surface to release IgA dimer into lumen
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9
Q

Solitary Nodules (follicles)

A
  • GI and Respiratory Tracts
  • contains mucosa and submucosa
  • unencapsulated - no CT layer around the nodule
  • Primary Nodule- naive B cell
  • Secondary Nodule- has a mantle and germinal center
  • Germinal center- activated immune cells ( B cells, t helper, dendritic)
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10
Q

Tonsils

A
  • Aggregated Nodules

- No CT, therefore not fully encapsulated and therefore aggregated nodules

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11
Q

Peyers Patches

A
  • Aggregated Nodules
  • Occur in ileum of GI Tract
  • Formed from lose lymphatic tissue and produce primary nodules, no germinal center
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12
Q

Microfold Cells

A
  • In Peyers Patches
  • Transport antigen to macrophages for stimulation of B and T cells
  • Helps initiate an immune response
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13
Q

Vermiform Appendix

A
  • Aggregated Nodule

- Contains much more lymphatic tissue in younger humans vs adult

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14
Q

Bone Marrow

A
  • Central lymphoid organ

- Encapsulated by endothelial cells

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15
Q

Thymus

A
  • Central lymphoid organ
  • site of T cell maturation- cortex
  • Bilobed
  • Contains cortex and medulla
  • Encapsulated
  • microframework of the thymus is formed by epithelial reticular cells
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16
Q

T cell positive and negative selection

A
  • T cells undergo somatic recombination in the thymus
  • if T cell recognizes self antigen, it is destroyed- Negative selection
  • If it does not recognize self antigen, it is released into circulation
  • 95% are self recognizing and are destoryed
17
Q

Blood - Thymus Barrier

A
  • Prevents formed elements of the blood coming into contact with thymocytes and other cells in those regions, stimulating an immune response
18
Q

Hassall’s Corpuscle

A
  • Unique to thymus
  • Found in Medulla of thymus
  • derived from medullary epithelial retricular cells
  • Keratinized
  • secretes thymic epithelizal cytokines
19
Q

Immunosenesecne

A
  • gradual deterioration of the immune system with age

- Lymphatic tissue greatly decreases

20
Q

Lymph Nodes

A
  • > 500 lymph nodes
  • filter of lyphatic vessels
  • Rich in nodes- neck, mediastinum, retroperitonium
  • Filter lymph and hold T and B cells
  • Lymphatic fluid comes in through afferent lymphatics, goes down various sinuses, and then exits through efferent lymphatics in the hilum
21
Q

Supericial Cortex of Lymph nodes

A
  • B cells and APCs
22
Q

Deep Cortex (paracortex)

A
  • T cells and APCs
23
Q

Postcapillary High Endothelial Venule (HEV)

A
  • Paracortex of lymph nodes
  • Lined with cuboidal endothelium
  • Lymphocytes squeeze through cuboidal cells and into blood vessels
24
Q

Spleen

A
  • Filters blood
  • Store Platelets
  • Extra medullary hematopoiesis - residual function observed in fetus
  • Red pulp- red blood cells
  • White pulp- abundance of leukocytes
25
Q

Periarterial Lymphatic sheath

A
  • Contains T cells

- Directly adjacent to central artery

26
Q

Peripheral White pulp

A
  • Contains B cells
27
Q

Blood Circulation of the Spleen

A
  • Passels through central artery, into white pulp, into marginal zone and back into central artery
  • Then it goes into red pulp, through venous sinusoids and into hepatic portal vein
28
Q

Closed vs Open Circulation

A
  • Sinusoid Open cirulation- Filtration slow 90%

- Sinusoid closed cirulation, fast 10%

29
Q

Splenic Sinusoids of Red Pulp

A
  • Blood cells flowing though the spleen must cross the sinusoidal wall to re enter the blood.
  • Only healthy blood cells can survive this fully intact
  • Macrophages are here to phagocytize the older red blood cells

Histology (25 decks)

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