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IHO Week 1 > Lymphatic System Histology > Flashcards

Lymphatic System Histology Flashcards

1
Q

Central lymphatic tissues

A

Bone marrow: source of B-cells

Thymus: source of T-cells

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2
Q

Peripheral lymph tissue

A

Mucosa-associated lymphatic tissue or nodular non-encapsulated lymphatic tissue
Lymph nodes
Spleen

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3
Q

Components of Lymphoid tissues

A

Stroma (cells - fibroblasts, APCs, DCs, FDCs, reticular fibers), lymphoid cells

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4
Q

Non-encapsulated Lymphatic tissues

A

Diffuse (GI, respiratory, GU, etc.) - dense or loose

Nodular (GI, respiratory, GU, etc)

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5
Q

Lymphatic nodules role vs lymph nodes

A

localized production of lymphocytes

smaller, no capsule, not a filter (no lymph vessel)

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6
Q

Primary lymphatic nodule

A

dark staining spherical balls of lymphocytes

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7
Q

secondary lymphatic nodule

A

contain a reaction (germinal) center

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8
Q

Cells of germinal center (secondary lymphatic nodule)

A

Large & medium lymphocytes (mostly Bs - mitotic)
Small lymphocytes (B and T - not mitotic)
Macrophages
FDCs
Plasma cells

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9
Q

Follicular Dendritic Cell

A

Special cell used to select lymphocytes involved in the generation of antibody and memory.
These are not true DC because they do not present antigen – just morphologically look like DC.

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10
Q

Occurrence of Lymphatic Nodules

A

Solitary, lymph nodes, spleen

NOT THE THYMUS

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11
Q

Examples of non-encapsulated nodular lymphatic tissue

A

Tonsil (palatine, lingual, pharyngeal and tubal)
Peyer’s patches
Appendix

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12
Q

Functions of non-encapsulated lymphatic tissues

A

trapping of antigen
Lymphocyte production in response to antigen (B cell proliferation)
Destruction of antigen
Selection of memory lymphocytes

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13
Q

Encapsulated lymphatic tissues

A

lymph node, spleen, thymus

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14
Q

Only lymphatic organ located in course of lymphatic vessels

A

lymph node

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15
Q

Only lymphatic organ that has lymphatic sinuses

A

Lymph node

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16
Q

Only lymphatic organ that filters lymph

Done by macrophages

A

Lymph node

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17
Q

Morphological features

A

Capsule, trabeculae, stroma (cells, fibers), endothelial cells

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18
Q

Divisions of lymph node

A

cortex and medulla

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19
Q

cortex of lymph node

A

Lymphoid tissue supported by reticular fibers & stromal cells
Lymphocytes
Lymphatic nodules
Germinal centers
Transient
Have tails that extend into medulla as medullary cords
Stromal cells

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20
Q

Lymphatic sinus flow

A

Afferent Lymphatic vessel to Subcapsular sinus to Trabecular sinus to Paracortical sinus to Medullary sinus to Efferent Lymphatic vessel

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21
Q

Medulla of lymph node

A

Lymphoid tissue supported by reticular fibers & stromal cells
Consists of medullary cords & medullary sinuses
Cells: small lymphocytes; differentiating and mature plasma cells; macrophages

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22
Q

Cortical subdivisions of lymph node

A

Superficial cortex

Mid-cortex

Deep cortex (paracortex)

23
Q

Superficial cortex lymph node

A

Between capsule & outer limits of germinal centers

Majority of cells are B-lymphocytes

24
Q

Midcortex of lymph nodes

A

Area containing the germinal centers

Primarily B-cells

25
Q

Deep cortex of lymph nodes

A

Between germinal centers & medullary cords

Majority of cells are T-lymphocytes

26
Q

Medullary cords are

A

mainly b and plasma cells

27
Q

Blood flow LN

A

Arterial vessels (at hilus)
Trabecular vessels
Arterioles & capillaries
Post-capillary venules
Outer (superficial & mid): simple squamous epithelium
Deep (paracortex): simple cuboidal endothelium (HEV’s)
Venous vessels (at hilus)

28
Q

HEV

A

Site of passage of lymphocytes (T- & B-lymphocytes) from blood vessels into lymphatic tissue
These lymphocytes then re-circulate via the efferent lymphatics back into the blood vascular system

29
Q

Sources of lymphocytes to lymph nodes

A

Mitotic division of cells in nodules
Circulating lymphocytes (Pathway: afferent arterioles; pre-capillary arterioles; capillaries; post-capillary venules (HEV’s); lymphatic tissue; lymphatic sinuses; efferent lymphatic vessels)
Afferent lymphatic vessels

30
Q

Lymph node functions

A 
Lymph filter (macrophages)
Lymphocyte production
Antibody production (plasma cells)
31
Q

Thymus

A

Site of differentiation of T lymphocyts

32
Q

Thymus size

A

Size (proportionally) largest during fetal & first 2 years of postnatal life
Increases in size up to puberty
Regresses in size as we subsequently age

33
Q

Thymus development

A

endoderm of third branchial pouch

–> reticualr stroma of thymus and hassals corpuscles

34
Q

Reticular stroma of thymus composed almost entirely of

A

epithelial reticular cells (no reticular fibers)

35
Q

Morphological features of thymus

A

Two lobes
Enclosed by connective tissue capsule
Beneath sternum on upper anterior thoracic wall
Divided into incomplete lobules by c.t. trabeculae or septae

Cortex and medulla

36
Q

Cells of cortex of thymus

A

epithelial reticular cells (endoderm, produce thymic hormones, blood-thymus barrier, support)

Macrophages
Lymphocytes (outer = stem cells, middle, proliferation and differentiation, inner - smallest, no mitoses, mature at corticomedullary junciton)
37
Q

Thymic hormones

A

Promote differentiation of stem cells into T-cells

Induce formation of T-cell surface markers

38
Q

thymus medulla

A

Epithelial reticular cells
Some lymphocytes
Some connective tissue cells and fibers
Hassall’s (thymic) corpuscles

39
Q

Thymus vascular supply

A

Major branches: internal thoracic and inferior thyroid arteries

Cortex
Small arteries & arterioles at corticomedullary (c-m) junction
Cortical anastomsing capillary loops
Post-capillary venules at c-m junction
Venous drainage away from thymus
Medulla
Small arteries & arterioles
Capillaries
Post-capillary venules
Venous drainage away from thymus
40
Q

Blood-thymus barrier

A

Prevents antigens in blood stream from entering the thymic cortex

Endothelial cells, basal lamina, perivascular space, basal lamina, epithelial reticular cells with desmosomes

41
Q

Spleen gross features

A

Hilus
Thick capsule with some smooth muscle
Thick connective tissue trabeculae
Splenic pulp (white & red)

NO CORTEX OR MEDULLA

42
Q

Splenic pulp consists of

A

blood cells embedded in, and supported by, a reticular fiber stromal network

43
Q

two types of splenic pulp

A

red, white

44
Q

white splenic pulp

A

2 compartments:
Periarterial lymphatic sheaths (PALs)
- Surround white pulp artery (central artery)
- Contain primarily T-cells

Splenic (lymphatic) nodules

  • Scattered throughout the splenic pulp
  • Contain primarily B-cells (except in area associated with white pulp or central artery)
45
Q

PALs

A
  • Surround white pulp artery (central artery)

- Contain primarily T-cells

46
Q

Splenic lymphatic nodues

A

Scattered throughout the splenic pulp

Contain primarily B-cells (except in area associated with white pulp or central artery)

47
Q

Red splenic pulp

A

Splenic sinuses (sinusoids)

  • Vascular passageways
  • Lined by specialized endothelial cells

Splenic cords (Billroth cords)

  • Located between sinuses
  • Contain: red blood cells; granulocytes; lymphocytes; macrophages; platelets; plasma cells; reticular cells & fibers
48
Q

Marginal zone (spleen)

A

The transitional zone between the red & white pulp

Small blood vessels dump their blood into this area

Recirculating lymphocytes return to enter either the periarterial lymphoid sheaths or the splenic nodules

49
Q

what kinds of cells in PALS vs splenic nodules

A

T cells in PALs

B cells in splenic nodules

50
Q

Splenic circulation

A

splenic artery – trabecular artery – white pulp or central artery – penicillus OR follicular artery – venous sinusoids or red pulp – pulp veins – trabecular veins – splenic veins

51
Q

closed vs open circulation (spleen)

A

Closed circulation
Terminal capillaries open into sinusoids

Open circulation
Terminal capillaries open into red pulp
Humans use open

52
Q

spleen sinusoids

A

Consist of elongated and narrow endothelial cells

Endothelial cells supported by an anastomosing ring of basement membrane and reticular fibers that encircle the sinusoid like the hoops of a barrel

53
Q

Splenic immune functions

A

Antibody presentation by APCs
Mostly dendritic cells and macrophages

Activation and proliferation of B and T lymphocytes

Production of antibodies against antigen present in circulating blood

Removal of macromolecular antigens from the blood

54
Q

Splenic hematopoietic functions

A

Removal and destruction of senescent, damaged, and abnormal erythrocytes and platelets
Retrieval of iron from erythrocyte hemoglobin
Formation of erythrocytes & granulocytes during early fetal life
Storage of blood, especially red blood cells and platelets

IHO Week 1 (9 decks)

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