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Histology > Lymphoid Organs > Flashcards

Lymphoid Organs Flashcards

1
Q

what are dense lymphoid tissues and give examples

A

organized into discreet structures or organs

-lymph nodes, spleen, thymus, tonsil

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2
Q

what are diffuse lymphoid tissues

A

located throughout the body, associated with mucous membranes

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3
Q

what lymphoid structures are associated with mucous membranes

A

respiratory and digestive tracts such as MALT

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4
Q

what do diffuse and dense lymphoid tissue both contain

A

large numbers of lymphocytes

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5
Q

what happens in primary lymphoid tissues

A

lymphoid tissue where B and T cells acquire surface receptors

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6
Q

what are primary lymphoid tissues for B cells? T cells?

A

-B cells: bone marrow
-T cells: thymus

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7
Q

what happens in secondary lymphoid tissues

A

mature B and T cells migrate to these tissues

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8
Q

what are lymphomas

A

malignant tumors of immune system when they involve solid organs

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9
Q

what are leukemias

A

malignant tumors of the immune system when they involve blood

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10
Q

what are lymphatic vessels

A

network of blind-ended vessels in connective tissue

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11
Q

what are the functions of lymphatic vessels

A

-provide a route which allows cells and large molecules in ECS to re-enter blood stream
- assist circulation of lymphocytes, concentrate antigen for elimination within lymph nodes

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12
Q

what are lymph nodes

A

encapsulated aggregates of lymphocytes and lymphoid tissue, distributed throughout the body

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13
Q

what are lymph nodes arranged in

A

chains or clusters along vessels of lymphatic origin

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14
Q

what are examples of lymph nodes

A

submandibular, cervical, axillary, femoral, popliteal, hilar lymph node

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15
Q

what are the 4 functions of lymph node

A

-non-specific filtering of particulate matter and microorganisms from lymph
- interaction of circulating lymphocytes with antigen in lymph
- aggregation, activation and proliferation of B-cells with subsequent antibody production
- aggregation and proliferation of T cells and induction of cytotoxic immunity

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16
Q

what are lymphoid cells

A

lymphocytes of all types, derived from bone marrow; enter node via bloodstream

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17
Q

what are immune accessory cells and give examples

A

antigen presenting cells (macrophages, B cells and T cells, originate in bone marrow)

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18
Q

what are follicular dendritic cells and where are they found

A

macrophages at periphery of germinal centers; antigen presenting cells
- found in one location in the lymph node

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19
Q

what are tingible body macrophages and where are they found

A

primarily found in germinal centers; possess numerous phagocytic vesicles

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20
Q

what are stromal cells

A

fibroblasts and reticular cells

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21
Q

what are reticular cells

A

fibroblast like cells with phagocytic capability

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22
Q

what forms the connective tissue skeleton of lymph nodes

A

stromal cells and extracellular products such as collagen and reticular fibers

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23
Q

does the lymph node have a cortex and a medulla

A

yes

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24
Q

describe the outer capsule of the lymph node

A

fibrous capsule of dense irregular CT

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25
Q

describe the outer cortex of the lymph node

A

dense outer cellular cortex, containing B cells, T cells, and plasma cells

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26
Q

describe the inner medulla of the lymph node

A

less cellular inner medulla containing B cells

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27
Q

what are medullary cords

A

extensions of cortical tissue into medulla

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28
Q

what are medullary sinuses

A

broad lymphatic channels that separate medullary cords

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29
Q

what are trabeculae and where are they located and what is their function

A

-very thin and collagenous
- interspersed throughout cortex and medulla
- provide support

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30
Q

where do vessels enter and exit the lymph node

A

the hilus

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31
Q

what does the hilus look like in a microscope slide

A

indented area at the end of lymph node

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32
Q

how do B cells and T cells leave the bloodstream and enter the node

A

diapedesis

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33
Q

what is diapedesis facilitated by

A

complementary adhesion molecules (addressins) present on endothelial cells and lymphocytes

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34
Q

what do WBCs migrate across in diapedesis

A

walls of specialized post capillary venules called high endothelial venules

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35
Q

what are high endothelial venules lined by and where are they located

A

lined by cuboidal to columnar endothelium, located in deep inner cortex of node at corticomedullary junction called the paracortical zone

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36
Q

what is the subcapsular sinus

A

space beneath the capsule in lymph node where numerous afferent lymph vessels drain into

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37
Q

describe the endothelium of the subcapsular sinus

A

on the side adjacent to capsule continuous (prevents leakage) but discontinuous on side adjacent to parenchyma

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38
Q

what are lymphatic sinuses filled with

A

reticular fibers and macrophage processes

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39
Q

what are the sinuses in the outer cortex of lymph nodes

A

-cortical sinuses
-trabecular sinuses
-peritrabecular sinuses

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40
Q

what do sinuses in the outer cortex drain into

A

medullary sinuses

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41
Q

describe medullary sinuses and what do they contain

A

-broad, lymphatic channels in inner, less cellular medulla
-contain lymphocytes, plasma cells and macrophages

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42
Q

where do medullary sinuses converge

A

hilus

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43
Q

where does lymph drain from the hilus

A

a single efferent lymph vessel that eventually returns to bloodstream via thoracic duct or R lymphatic duct

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44
Q

what is lymphatic drainage to regional lymph nodes important in

A

metastasis of tumor cells

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45
Q

what is the cortex of the lymph node mainly made of

A

B cells

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46
Q

is the cortex of the lymph node uniform

A

no some areas are more dense than others

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47
Q

what are lymphoid follicles and where are they located

A

within the cortex of the lymph node they are densely packed and highly cellular

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48
Q

which follicles contain a germinal center

A

secondary follicles

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49
Q

what do germinal centers in follicles indicate

A

the node is responding to anitgens

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50
Q

how do lymphocytes respond to antigen

A

by increased antibody production via clonal expansion

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51
Q

what are secondary hemopoiesis and what do they contain

A

sites of B cell proliferation, contain lymphoblasts, macrophages and immature B cells and T cells

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52
Q

what is the cause of lymph node enlargement and swollen glands

A

proliferation of lymphocytes

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53
Q

what is the mantle zone

A

-darker staining rim surrounding germinal center
-region of antigen presentation

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54
Q

what is the thymus and where is it located

A

lobular, lymphatic organ located in mediastinum

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55
Q

what is the thymus embryologically derived from

A

epithelial outgrowth of 3rd pharyngeal pouch

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56
Q

what is the thymus important for in fetal development

A

important hematopoietic organ

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57
Q

what is the thymus similar in appearance to and with what exceptions

A

the lymph node, but lacks lymphoid follicles and medulla lacks medullary cords and sinuses

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58
Q

what is the capsule in the thymus made of

A

dense, irregular connective tissue

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59
Q

what divides the thymus into lobules

A

interlobular septa or trabeculae

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60
Q

what are the functions of the thymus

A

-production of mature, immunocompetent Th and Tc cells
-clonal proliferation of Tc cells
-clonal deletion of self antibodies
-secretion of hormones regulating t-cell development and maturation

61
Q

what might the failure of clonal deletion result in

A

autoimmune diseases

62
Q

what does clonal deletion of self antibodies do

A

develop immunologic self tolerance

63
Q

what do t-cells express as they mature

A

-antigen specific t-cell receptors
- CD surface markers
- Class I and II HLA surface markers

64
Q

what does the cortex in the thymus mainly contain

A

T cells

65
Q

describe the cortex of the thymus and what it contains

A

highly cellular packed with lymphocytes, mostly T cells and macrophages

66
Q

what follicles are in the cortex of the thymus

A

primary follicles only

67
Q

does the cortex of the thymus have clonal expansion of t-cells

A

limited

68
Q

describe the medulla of the thymus and what it contains

A

less cellular contains mostly B cells, plasma cells and macrophages

69
Q

what are nurse cells and what do they do

A

epithelial cells within thymus (cortex and medulla),
provide nurse function and structural support
-secretes hormones that attract regulate and promote t- cell proliferation and differentiation into Tc, Ts, and Th cells

70
Q

what do nurse cells secrete

A

thymotaxin, thymosin, thymopoietin

71
Q

what are hassal’s corpuscles

A

eosinophilic, lamellated structures within medulla and cortex that represent degenerate reticular and epithelial nurse cells

72
Q

what is a key identifier of the thymus

A

hassal’s corpuscles

73
Q

describe the thymus at puberty and in adults

A

degenerates at puberty and vestigial in adults

74
Q

what is thymic involution

A

thymus undergoes fatty infiltration and lymphatic depletion

75
Q

what does the inner surface of the capsule of the thymus contain

A

continuous epithelium to isolate thymus

76
Q

why are there no afferent lymph vessels to the thymys

A

because t-cells are not fully differentiated

77
Q

what type of lymph vessels are present in the thymus and what do they do

A

only efferent to drain lymph

78
Q

what is the blood thymus barrier

A

connective tissue sheath that surrounds thymic blood vessels

79
Q

what does the blood thymus barrier do

A

forms continuous antigenic barrier around endothelium and basement membrane of blood vessels that isolates thymus from immune system

80
Q

what makes up the blood thymus barrier

A

epithelioreticular cells, reticular fibers, fibroblasts, macrophages, plasma cells

81
Q

what is the largest lymphoid organ in the body

A

the spleen

82
Q

what are the immune functions of the spleen

A

-B and T cell replication, manufacturing of antibodies, antigen removal
-removes particulate matter and aged or defective RBC’s from circulation via phagocytosis
- recycles iron from hemoglobin
-hemopoiesis in fetus

83
Q

what takes over the function of the spleen if it is removed

A

liver and bone marrow

84
Q

describe the capsule of the spleen

A

dense, fibro elastic outer capsule contains smooth muscle cells and acts as a resevoir for RBCs

85
Q

what are the trabeculae of the spleen made of, where are they located and what do they contain

A

-thick bands of dense CT
- extend in body of spleen
-contain trabecular arteries and veins

86
Q

does the spleen have a cortex or medulla

A

no neither

87
Q

what is the bulk of the spleen composed of

A

spongy matrix of red pulp

88
Q

what is in the red pulp of the spleen

A

pulp cords and sinusoids

89
Q

what do sinusoids contain

A

mostly blood

90
Q

what do pulp cords contain

A

large numbers of macrophages and lymphocytes

91
Q

are pulp cords or sinusoids more cellular

A

pulp cords

92
Q

what are pulp cords supported by

A

connective tissue skeleton of reticular cells and reticular fibers

93
Q

what does white pulp contain in spleen

A

large number of WBCs
- follicular areas that may or may not have germinal centers

94
Q

what do follicular areas in white pulp contain

A

primarily B cells

95
Q

what is in the middle of white pulp

A

central artery

96
Q

what is the white pulp surrounded by

A

a thin basophilic mantle zone surrounded by paler marginal zone

97
Q

what is the function of white pulp and what cells does it contain

A

antigen presentation, phagocytosis; contains large numbers of macrophages, plasma cells and T helper cells

98
Q

what are splenic nodules

A

enlarged germinal centers visible to naked eye

99
Q

what forms periarteriolar lymphatic sheaths (PALS)

A

T cells that surround the central artery

100
Q

do PALS have germinal centers

A

no

101
Q

what do PALS require for ID

A

immunohistochemical staining

102
Q

what is another term for PALS

A

primary follicles in white pulp

103
Q

how do branches of the splenic artery enter the spleen

A

within trabeculae via trabecular arteries

104
Q

what do trabecular arteries branch and form in the spleen

A

central artery to white pulp

105
Q

where do central arteries run

A

into red pulp where they branch into perpendicular penicillar arteries

106
Q

what do penicillar arteries branch into in the spleen

A

arterioles and terminate into 2-3 sheathed capillaries

107
Q

what do blind ending capillaries lack

A

endothelial lining

108
Q

what surrounds blind ending capillaries

A

macrophages

109
Q

what do sheathed capillaries form in the spleen

A

a non-continuous perivascular sheath or cuff that acts as part of filtering mechanism, active in phagocytosis

110
Q

how do blood cells leave sheathed capillaries in the spleen

A

diapedesis

111
Q

where do blood cells enter sinuses in the spleen

A

in red pulp

112
Q

what are stave cells

A

endothelial cells that line sinusoids

113
Q

what do endothelial slits between stave cells allow

A

free passage of blood cells

114
Q

how does blood drain out of spleen

A

trabecular veins -> splenic vein

115
Q

what are palatine tonsils and where are they located

A

paired structures located at the junction of oral and pharyngeal cavities within tonsillar crypts between anterior and posterior tonsillar pillars called palatoglossal and palatopharyngeal arches

116
Q

where are lingual tonsils located and what are they associated with

A

at the base of tongue and pharyngeal tonsils in nasopharynx, associated with eustacian tubes

117
Q

what are adenoids

A

pharyngeal tonsils

118
Q

what makes up Waldeyer’s ring

A

palatal, lingual and pharyngeal tonsils

119
Q

what makes up NALT

A

palatal and pharyngeal tonsils

120
Q

describe the capsule of palatine tonsils

A

unencapsulated but supported by a cup shaped collagenous hemi capsule

121
Q

do the palatine tonsils have cortex and medulla

A

no

122
Q

describe the follicles in palatine tonsils

A

scattered throughout parenchyma, may or may not include germinal centers

123
Q

what is the luminal surface of palatine tonsils and lingual tonsils covered by

A

stratified squamous nonkeratinized epithelium

124
Q

what does the epithelium in palatine tonsils form

A

blind-ended tonsilar crypts

125
Q

how do you identify lymph node

A

cortex with primary and secondary follicles and medulla with medullary cords and sinusoids

126
Q

how do you identify thymus

A

mostly T cells; Hassal’s corpuscles; cortex and medulla present

127
Q

how do you identify the spleen

A

robust capsule and trabeculae, no cortex and medulla, red and white pulp instead

128
Q

how do you identify the palatine tonsil

A

hemicapsule and skin-like epithelium with crypts, no cortex and medulla

129
Q

describe the appendix

A

blind-ended sac, vestigial cecum

130
Q

what happens to the appendix in adults and what does it contain

A

atrophies, contains mostly B bells

131
Q

what is the appendix used for in herbivores

A

important digestive organ in herbivores used for bacterial fermentation

132
Q

descirbe the different components of MALT

A

in gut = GALT
in respiratory tract = BALT
in pharynx = NALT

133
Q

what is MALT

A

-mucosa associated lymphoid tissue
-diffuse, unencapsulated lymphoid aggregates associated with mucosal surfaces

134
Q

where is MALT located

A

subepithelial connective tissue of lamina propria

135
Q

what does MALT mainly contain

A

B cells

136
Q

what does MALT produce and where is it secreted

A

IgA that are secreted onto the mucosal surface

137
Q

describe the follicles in MALT

A

may or may not contain germinal centers

138
Q

what is the function of MALT

A

samples antigenic material
produces lymphoblasts
secretes antibodies

139
Q

what does MALT in gut contain and where are they located

A

specialized M-cells- squamoid enterocytes
- located in surface epithelium with microfolds on surface

140
Q

how does MALT participate in antigen sampling

A

transfers antigen from gut lumen into lymphoid follicles

141
Q

when is MALT formed

A

during fetal development

142
Q

when is MALT distribution at maximum

A

in childhood, progressively atrophies with age

143
Q

what are peyers patches and where are they most common and least common

A

special type of MALT scattered throughout small intestine
- most common in ileum, least in duodenum

144
Q

where do peyers patches project

A

into lumen of gut in dome areas with cuboidal mucosa

145
Q

what do peyers patches contain

A

M-cells, B cells, and T cells

146
Q

what are peyers patches histologically similar to

A

MALT

147
Q

do peyers patches produce large amounts of IgA

A

no

148
Q

describe the presence of germinal centers in peyers patches

A

frequent; associated with foci of B cells

Histology (27 decks)

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