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IHO Week 1 > Lymphatic System Histology > Flashcards

Lymphatic System Histology Flashcards

(54 cards)

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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

Study These Flashcards
A

Superficial cortex

Mid-cortex

Deep cortex (paracortex)

23
Q

Superficial cortex lymph node

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A

Between capsule & outer limits of germinal centers

Majority of cells are B-lymphocytes

24
Q

Midcortex of lymph nodes

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A

Area containing the germinal centers

Primarily B-cells

25
Deep cortex of lymph nodes
Between germinal centers & medullary cords | Majority of cells are T-lymphocytes
26
Medullary cords are
mainly b and plasma cells
27
Blood flow LN
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
HEV
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
Sources of lymphocytes to lymph nodes
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
Lymph node functions
``` Lymph filter (macrophages) Lymphocyte production Antibody production (plasma cells) ```
31
Thymus
Site of differentiation of T lymphocyts
32
Thymus size
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
Thymus development
endoderm of third branchial pouch | --> reticualr stroma of thymus and hassals corpuscles
34
Reticular stroma of thymus composed almost entirely of
epithelial reticular cells (no reticular fibers)
35
Morphological features of thymus
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
Cells of cortex of thymus
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
Thymic hormones
Promote differentiation of stem cells into T-cells | Induce formation of T-cell surface markers
38
thymus medulla
Epithelial reticular cells Some lymphocytes Some connective tissue cells and fibers Hassall’s (thymic) corpuscles
39
Thymus vascular supply
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
Blood-thymus barrier
Prevents antigens in blood stream from entering the thymic cortex Endothelial cells, basal lamina, perivascular space, basal lamina, epithelial reticular cells with desmosomes
41
Spleen gross features
Hilus Thick capsule with some smooth muscle Thick connective tissue trabeculae Splenic pulp (white & red) NO CORTEX OR MEDULLA
42
Splenic pulp consists of
blood cells embedded in, and supported by, a reticular fiber stromal network
43
two types of splenic pulp
red, white
44
white splenic pulp
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
PALs
- Surround white pulp artery (central artery) | - Contain primarily T-cells
46
Splenic lymphatic nodues
Scattered throughout the splenic pulp | Contain primarily B-cells (except in area associated with white pulp or central artery)
47
Red splenic pulp
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
Marginal zone (spleen)
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
what kinds of cells in PALS vs splenic nodules
T cells in PALs | B cells in splenic nodules
50
Splenic circulation
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
closed vs open circulation (spleen)
Closed circulation Terminal capillaries open into sinusoids Open circulation Terminal capillaries open into red pulp Humans use open
52
spleen sinusoids
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
Splenic immune functions
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
Splenic hematopoietic functions
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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