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
2
Q
what are diffuse lymphoid tissues
A
located throughout the body, associated with mucous membranes
3
Q
what lymphoid structures are associated with mucous membranes
A
respiratory and digestive tracts such as MALT
4
Q
what do diffuse and dense lymphoid tissue both contain
A
large numbers of lymphocytes
5
Q
what happens in primary lymphoid tissues
A
lymphoid tissue where B and T cells acquire surface receptors
6
Q
what are primary lymphoid tissues for B cells? T cells?
A
-B cells: bone marrow
-T cells: thymus
7
Q
what happens in secondary lymphoid tissues
A
mature B and T cells migrate to these tissues
8
Q
what are lymphomas
A
malignant tumors of immune system when they involve solid organs
9
Q
what are leukemias
A
malignant tumors of the immune system when they involve blood
10
Q
what are lymphatic vessels
A
network of blind-ended vessels in connective tissue
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
12
Q
what are lymph nodes
A
encapsulated aggregates of lymphocytes and lymphoid tissue, distributed throughout the body
13
Q
what are lymph nodes arranged in
A
chains or clusters along vessels of lymphatic origin
14
Q
what are examples of lymph nodes
A
submandibular, cervical, axillary, femoral, popliteal, hilar lymph node
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
16
Q
what are lymphoid cells
A
lymphocytes of all types, derived from bone marrow; enter node via bloodstream
17
Q
what are immune accessory cells and give examples
A
antigen presenting cells (macrophages, B cells and T cells, originate in bone marrow)
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
19
Q
what are tingible body macrophages and where are they found
A
primarily found in germinal centers; possess numerous phagocytic vesicles
20
Q
what are stromal cells
A
fibroblasts and reticular cells
21
Q
what are reticular cells
A
fibroblast like cells with phagocytic capability
22
Q
what forms the connective tissue skeleton of lymph nodes
A
stromal cells and extracellular products such as collagen and reticular fibers
23
Q
does the lymph node have a cortex and a medulla
A
yes
24
Q
describe the outer capsule of the lymph node
A
fibrous capsule of dense irregular CT
25
describe the outer cortex of the lymph node
dense outer cellular cortex, containing B cells, T cells, and plasma cells
26
describe the inner medulla of the lymph node
less cellular inner medulla containing B cells
27
what are medullary cords
extensions of cortical tissue into medulla
28
what are medullary sinuses
broad lymphatic channels that separate medullary cords
29
what are trabeculae and where are they located and what is their function
-very thin and collagenous
- interspersed throughout cortex and medulla
- provide support
30
where do vessels enter and exit the lymph node
the hilus
31
what does the hilus look like in a microscope slide
indented area at the end of lymph node
32
how do B cells and T cells leave the bloodstream and enter the node
diapedesis
33
what is diapedesis facilitated by
complementary adhesion molecules (addressins) present on endothelial cells and lymphocytes
34
what do WBCs migrate across in diapedesis
walls of specialized post capillary venules called high endothelial venules
35
what are high endothelial venules lined by and where are they located
lined by cuboidal to columnar endothelium, located in deep inner cortex of node at corticomedullary junction called the paracortical zone
36
what is the subcapsular sinus
space beneath the capsule in lymph node where numerous afferent lymph vessels drain into
37
describe the endothelium of the subcapsular sinus
on the side adjacent to capsule continuous (prevents leakage) but discontinuous on side adjacent to parenchyma
38
what are lymphatic sinuses filled with
reticular fibers and macrophage processes
39
what are the sinuses in the outer cortex of lymph nodes
-cortical sinuses
-trabecular sinuses
-peritrabecular sinuses
40
what do sinuses in the outer cortex drain into
medullary sinuses
41
describe medullary sinuses and what do they contain
-broad, lymphatic channels in inner, less cellular medulla
-contain lymphocytes, plasma cells and macrophages
42
where do medullary sinuses converge
hilus
43
where does lymph drain from the hilus
a single efferent lymph vessel that eventually returns to bloodstream via thoracic duct or R lymphatic duct
44
what is lymphatic drainage to regional lymph nodes important in
metastasis of tumor cells
45
what is the cortex of the lymph node mainly made of
B cells
46
is the cortex of the lymph node uniform
no some areas are more dense than others
47
what are lymphoid follicles and where are they located
within the cortex of the lymph node they are densely packed and highly cellular
48
which follicles contain a germinal center
secondary follicles
49
what do germinal centers in follicles indicate
the node is responding to anitgens
50
how do lymphocytes respond to antigen
by increased antibody production via clonal expansion
51
what are secondary hemopoiesis and what do they contain
sites of B cell proliferation, contain lymphoblasts, macrophages and immature B cells and T cells
52
what is the cause of lymph node enlargement and swollen glands
proliferation of lymphocytes
53
what is the mantle zone
-darker staining rim surrounding germinal center
-region of antigen presentation
54
what is the thymus and where is it located
lobular, lymphatic organ located in mediastinum
55
what is the thymus embryologically derived from
epithelial outgrowth of 3rd pharyngeal pouch
56
what is the thymus important for in fetal development
important hematopoietic organ
57
what is the thymus similar in appearance to and with what exceptions
the lymph node, but lacks lymphoid follicles and medulla lacks medullary cords and sinuses
58
what is the capsule in the thymus made of
dense, irregular connective tissue
59
what divides the thymus into lobules
interlobular septa or trabeculae
60
what are the functions of the thymus
-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
what might the failure of clonal deletion result in
autoimmune diseases
62
what does clonal deletion of self antibodies do
develop immunologic self tolerance
63
what do t-cells express as they mature
-antigen specific t-cell receptors
- CD surface markers
- Class I and II HLA surface markers
64
what does the cortex in the thymus mainly contain
T cells
65
describe the cortex of the thymus and what it contains
highly cellular packed with lymphocytes, mostly T cells and macrophages
66
what follicles are in the cortex of the thymus
primary follicles only
67
does the cortex of the thymus have clonal expansion of t-cells
limited
68
describe the medulla of the thymus and what it contains
less cellular contains mostly B cells, plasma cells and macrophages
69
what are nurse cells and what do they do
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
what do nurse cells secrete
thymotaxin, thymosin, thymopoietin
71
what are hassal's corpuscles
eosinophilic, lamellated structures within medulla and cortex that represent degenerate reticular and epithelial nurse cells
72
what is a key identifier of the thymus
hassal's corpuscles
73
describe the thymus at puberty and in adults
degenerates at puberty and vestigial in adults
74
what is thymic involution
thymus undergoes fatty infiltration and lymphatic depletion
75
what does the inner surface of the capsule of the thymus contain
continuous epithelium to isolate thymus
76
why are there no afferent lymph vessels to the thymys
because t-cells are not fully differentiated
77
what type of lymph vessels are present in the thymus and what do they do
only efferent to drain lymph
78
what is the blood thymus barrier
connective tissue sheath that surrounds thymic blood vessels
79
what does the blood thymus barrier do
forms continuous antigenic barrier around endothelium and basement membrane of blood vessels that isolates thymus from immune system
80
what makes up the blood thymus barrier
epithelioreticular cells, reticular fibers, fibroblasts, macrophages, plasma cells
81
what is the largest lymphoid organ in the body
the spleen
82
what are the immune functions of the spleen
-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
what takes over the function of the spleen if it is removed
liver and bone marrow
84
describe the capsule of the spleen
dense, fibro elastic outer capsule contains smooth muscle cells and acts as a resevoir for RBCs
85
what are the trabeculae of the spleen made of, where are they located and what do they contain
-thick bands of dense CT
- extend in body of spleen
-contain trabecular arteries and veins
86
does the spleen have a cortex or medulla
no neither
87
what is the bulk of the spleen composed of
spongy matrix of red pulp
88
what is in the red pulp of the spleen
pulp cords and sinusoids
89
what do sinusoids contain
mostly blood
90
what do pulp cords contain
large numbers of macrophages and lymphocytes
91
are pulp cords or sinusoids more cellular
pulp cords
92
what are pulp cords supported by
connective tissue skeleton of reticular cells and reticular fibers
93
what does white pulp contain in spleen
large number of WBCs
- follicular areas that may or may not have germinal centers
94
what do follicular areas in white pulp contain
primarily B cells
95
what is in the middle of white pulp
central artery
96
what is the white pulp surrounded by
a thin basophilic mantle zone surrounded by paler marginal zone
97
what is the function of white pulp and what cells does it contain
antigen presentation, phagocytosis; contains large numbers of macrophages, plasma cells and T helper cells
98
what are splenic nodules
enlarged germinal centers visible to naked eye
99
what forms periarteriolar lymphatic sheaths (PALS)
T cells that surround the central artery
100
do PALS have germinal centers
no
101
what do PALS require for ID
immunohistochemical staining
102
what is another term for PALS
primary follicles in white pulp
103
how do branches of the splenic artery enter the spleen
within trabeculae via trabecular arteries
104
what do trabecular arteries branch and form in the spleen
central artery to white pulp
105
where do central arteries run
into red pulp where they branch into perpendicular penicillar arteries
106
what do penicillar arteries branch into in the spleen
arterioles and terminate into 2-3 sheathed capillaries
107
what do blind ending capillaries lack
endothelial lining
108
what surrounds blind ending capillaries
macrophages
109
what do sheathed capillaries form in the spleen
a non-continuous perivascular sheath or cuff that acts as part of filtering mechanism, active in phagocytosis
110
how do blood cells leave sheathed capillaries in the spleen
diapedesis
111
where do blood cells enter sinuses in the spleen
in red pulp
112
what are stave cells
endothelial cells that line sinusoids
113
what do endothelial slits between stave cells allow
free passage of blood cells
114
how does blood drain out of spleen
trabecular veins -> splenic vein
115
what are palatine tonsils and where are they located
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
where are lingual tonsils located and what are they associated with
at the base of tongue and pharyngeal tonsils in nasopharynx, associated with eustacian tubes
117
what are adenoids
pharyngeal tonsils
118
what makes up Waldeyer's ring
palatal, lingual and pharyngeal tonsils
119
what makes up NALT
palatal and pharyngeal tonsils
120
describe the capsule of palatine tonsils
unencapsulated but supported by a cup shaped collagenous hemi capsule
121
do the palatine tonsils have cortex and medulla
no
122
describe the follicles in palatine tonsils
scattered throughout parenchyma, may or may not include germinal centers
123
what is the luminal surface of palatine tonsils and lingual tonsils covered by
stratified squamous nonkeratinized epithelium
124
what does the epithelium in palatine tonsils form
blind-ended tonsilar crypts
125
how do you identify lymph node
cortex with primary and secondary follicles and medulla with medullary cords and sinusoids
126
how do you identify thymus
mostly T cells; Hassal's corpuscles; cortex and medulla present
127
how do you identify the spleen
robust capsule and trabeculae, no cortex and medulla, red and white pulp instead
128
how do you identify the palatine tonsil
hemicapsule and skin-like epithelium with crypts, no cortex and medulla
129
describe the appendix
blind-ended sac, vestigial cecum
130
what happens to the appendix in adults and what does it contain
atrophies, contains mostly B bells
131
what is the appendix used for in herbivores
important digestive organ in herbivores used for bacterial fermentation
132
descirbe the different components of MALT
in gut = GALT
in respiratory tract = BALT
in pharynx = NALT
133
what is MALT
-mucosa associated lymphoid tissue
-diffuse, unencapsulated lymphoid aggregates associated with mucosal surfaces
134
where is MALT located
subepithelial connective tissue of lamina propria
135
what does MALT mainly contain
B cells
136
what does MALT produce and where is it secreted
IgA that are secreted onto the mucosal surface
137
describe the follicles in MALT
may or may not contain germinal centers
138
what is the function of MALT
samples antigenic material
produces lymphoblasts
secretes antibodies
139
what does MALT in gut contain and where are they located
specialized M-cells- squamoid enterocytes
- located in surface epithelium with microfolds on surface
140
how does MALT participate in antigen sampling
transfers antigen from gut lumen into lymphoid follicles
141
when is MALT formed
during fetal development
142
when is MALT distribution at maximum
in childhood, progressively atrophies with age
143
what are peyers patches and where are they most common and least common
special type of MALT scattered throughout small intestine
- most common in ileum, least in duodenum
144
where do peyers patches project
into lumen of gut in dome areas with cuboidal mucosa
145
what do peyers patches contain
M-cells, B cells, and T cells
146
what are peyers patches histologically similar to
MALT
147
do peyers patches produce large amounts of IgA
no
148
describe the presence of germinal centers in peyers patches
frequent; associated with foci of B cells
