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HemeOnc Block > Histo HemeOnc > Flashcards

Histo HemeOnc Flashcards

1
Q

Lymphatic system provides what?

A

immune response to antigens (proteins, carbs, lipids, or nucleic acids)

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2
Q

What are the effector cells of the lymphatic system? What are the three main types?

A

lymphocytes: B, T, NK

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3
Q

What are the supporting cells of the lymphatic system and what is their role?

A
  • stromal cells - support cells forming loose meshwork creating a good environment for lymphocytes
  • monocytes/macrophages, polymorphonuclear leukocytes, and dendritic cells - assist with antigen presentation and regulation of the immune response
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4
Q

What is innate immunity?

A
  • not specific,
  • does not require exposure to an antigen
  • functional at birth
  • natural barriers (physical or chemical)
  • phagocytic and NK cells
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5
Q

Adaptive immunity

A
  • specific
  • develops after exposure to antigen
  • induces resistance against pathogens
  • two types
    • humoral immunity
    • cell-mediated immunity
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6
Q

humoral immunity

A
  • mediated by abs acting on invading agent
  • abs produced by B lymphocytes and plasma cells
  • best against extracellular bacteria
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7
Q

Cell mediated immunity

A
  • Tc lymphocytes, NK cells, monocytes/macrophages, and polymorphonuclear leukocytes
  • attack and destroy virus infected host cells, foreign and tumor cells
  • effective v intracellular and extracellular pathogens
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8
Q

What are the two primary lymphatic organs?

A

bone marrow and thymus

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9
Q

initially, lymphocytes in the primary lymphatic organs are programmed to….

A

recognize a single antigen in process called antigen-independent proliferation and differentiation

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10
Q

What kind of tissue is bone marrow?

A

reticular connective tissue, filling the internal spaces of bone

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11
Q

How is bone marrow separated from the bone proper?

A

endosteum

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12
Q

How does blood get to the bone marrow cavity?

A

nutrient arteries through bone, into arterioles, into plexus of capillary sinusoids aka venous sinuses

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13
Q

What is the general structure of bone marrow?

A
  • hemopoietic cords of cells supported by reticular fibers surround the venous sinuses;
    • cords of cells contain blood cell precursors, mature blood cells, adipocytes, and stromal cells
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14
Q

Composition of bone marrow in young v old

A

younger people have fewer adipocytes in bone marrow and this is called “red marrow”

adults have more adipocytes in the bone marrow and are called “yellow marrow”

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15
Q

What are the stromal cells in bone marrow and what do they do?

A

CT cells like fibroblasts and macrophages; important role in secreation of facters to stimulate hemopoiesis like IL-11

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16
Q

Where do B cells become immunocompetent B cells?

A

bone marrow and MALT

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17
Q

Where do T cells become immunocompetent?

A

originate in bone marrow and then become immunocopetent in thymus

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18
Q

What does the organ of the thymus look like?

A

asymmetric, bilobed organ in the superior mediastinum on the posterier side of the manubrium of the sternum

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19
Q

At what point in life is the thymus the largest?

A

thymus is largest in kids and begins to regress at puberty

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20
Q

What pharyngeal pouches does the thymus originate from?

A

3rd and 4th pharyngeal pouches

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21
Q

When do CLP cells from the bone marrow invade the epithelium rudiment of the thymus?

A

about 10th week

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22
Q

What does the stroma of the thymus originate from?

A

endodermal origin

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23
Q

Where do lymphocytes and macrophages originate from?

A

mesodermal origin (bone marrow derived)

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24
Q

What is the most abundant cell of the thymus?

A

T lymphocyte aka thymocyte

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25
Q

How many of the T cells that start the differentiation process undergo apoptosis and are phagocytized?

A

98%

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26
Q

What cells support lymphocytes and provide framework for developing T cells? What are they like?

A

epithelioreticular cells

true epithelial cells and connected by occluding junctions and desmosomes forming a cytoreticulum; have basal lamina; DO NOT secrete reticular fibers like the true reticular cells of the LNs

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27
Q

In the thymus, what cells are dispersed among the T cells? What do they do?

A

Macrophages

responsible for phagocytosis of T cells that do not fulfill thymus education requirements

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28
Q

What is the histological structure of the thymus capsule?

A
  • well-developed CT capsule
  • divided into lobes
  • CT dives into parenchyma in thin struts, forming trabeculae, dividing the thymus into incomplete lobes
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29
Q

What is the cortex of the thymus like?

A
  • outer, densely cellular portion of each lobule
  • densely packed lymphocytes giving a basophilic appearance
  • least differentiated lymphocytes found here, then mature and go toward medulla
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30
Q

What is the medulla of the thymus like?

A
  • less cellular part of lobules
  • lighter stain than cortex
  • has mature, differentiated T cells, macrophages
  • Hassal’s corpuscles - concentric structures of epithelioreticular cells
    • center can have keratin pearl
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31
Q

What prevents antigens from escaping cortical capillaries into the thymus cortex to avoid contact with developing T cells?

A

Blood-thymus barrier

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32
Q

What are the three mechanisms of the blood-thymus barrier?

A
  • tight junctions between the endothelial cells of the thymus cortical continuous capillaries
  • perivascular CT surrounding caps is loaded with macrophages that phagocytose antigens that manage to get through epithelium
  • endothelioreticular cells form occluding junctions around capillaries and together w their basal laminae form the third component of the blood-thymus barrier
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33
Q

Vaguely, what is T cell education?

A
  • see if T cell is good enough to complete mission later
  • several steps, characterized by a change in the expression and deletion of certain surface markers
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34
Q

What is the earliest stage in T cell education? Where does this occur?

A

double negative stage

in outer cortex, close to the capsule of the thymus

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35
Q

What happens during the double-negative stage?

A

lymphocytes do not have either CD4 or CD8 and only posess CD2 and CD7 on their cell surface

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36
Q

Where does the double-positive stage occur? What is expressed at this time?

A

occurs in cortex of thymus

T cells expressing TCR, CD3, and both CD4 and CD8 on cell surface

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37
Q

What happens in the double-positive stage?

A

T cells are presented with both self-MHC and self- and foreign antigens

if they fail to recognize either they are eliminated;

the cells that do recognize those in the process (positive selection) leave the cortex and enter the medulla

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38
Q

What happens after positive selection? Where does this next step take place?

A

negative selection

in the medulla

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39
Q

What is the process of negative selection?

A

double positive cells in the medulla that recognize self-antigen presented by self-MHC are eliminated

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40
Q

Surviving cells of negative selection become what? What is this stage called?

What do the cells do now?

A

either CD8+ Tc or CD4+ T helper

lose the other CD marker so now they are single-positive stage

they are allowed to leave the thymus and enter circulation

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41
Q

What are the secondary lymphatic organs?

A

MALT, GALT, BALT, tonsils, LNs, and spleen

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42
Q

Where do lymphocytes undergo antigen-dependent activation?

A

secondary lymphatic organs

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43
Q

What is MALT typically formed of? (3 major manifestations)

A

diffuse lymphoid tissue

single lymphoid follicles

aggregated lymphoid follicles

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44
Q

What does not have a capsule and consists of loosely arranged immune cells?

A

diffuse lymphoid tissue

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45
Q

Where is diffuse lymphoid tissue mostly found?

A

lamina propria of the GIT, respiratory passages and GUT

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46
Q

After contact with antigen in diffuse lymphoid tissue, where do the lymphocytes go?

A

travel to lymph nodes where they undergo proliferation and differentiation;

progeny of these cells then return to lamina propria as effector B and T lymphocytes

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47
Q

What are lymphoid follicles and where can I find them?

A

spherical structures scattered throughout the lamina propria of the GIT, respiratory passages, and GUT; also found in LNs, spleen, and tonsils

lacking a capsule

48
Q

What cells compose lymphoid follicles?

A

B lymphocytes mostly

follicular dendritic cells express receptors for soluble immunoglobulins

49
Q

What do follicular dendritic cells do?

A

express receptors fo soluble immunoglobulins;

bind immunoglobulins, which will bind antigens

cells do not readily endocytose the immunoglobulin receptors and antigens bound to these receptors are stored on the surface of the cells for long time

important in maintenance of memory B cells and in the selection of B cells with very high affinity antibodies

50
Q

What is the difference between primary and secondary lymphoid follicles?

A
  • primary
    • no dividing lymphocytes
    • uniformly composed of small lymphocytes
    • B cells that have not yet been activated
  • secondary
    • dividing lymphocytes
    • contain activated B cells
    • develop after a lymphocyte that has recognized and antigen in the mucosa returns to a primary follicle and undergoes proliferation
      • has germinal center and mantle
51
Q

What does the germinal center of secondary lymphoid follicles contain?

A

large activated immatrue lymphocytes (lymphoblasts) that are undergoing mitoses

lighter staining than the mature small lymphocytes

follicular dendritic cells are also present

52
Q

What does the mantle (aka corona) of the secondary lymphoid follcile contain?

A
  • contains small lymphocytes that surround the germinal center creating characteristic bull’s eye appearance
53
Q

Where are aggregated lymphoid follicles found?

A
  • peyers patches are in the lamina propria of the ileum and consist of numerous lymphoid follicles
  • lamina propria of the vermiform appendix is heavily infiltrated w lymphocytes and contains numerous lymphoid follicles
54
Q

What forms a ring of lymphatic tissue at the entrance of the oropharynx? What are they composed of?

A

tonsils

aggregates of lymphoid follicles

55
Q

What are the largest of the three kinds of tonsils? Where are they located?

A

Palatine tonsils

located on the posterior part of the soft palate between the palatopharyngeal and palatoglossal arches

56
Q

What is the epithelium of palatine tonsils like?

A

non-keratinized stratified squamous epithelium, making multiple dips into the tissue of the tonsil forming the tonsillar crypts

57
Q

What is the epithelium of the tonsillar crypts like?

A

thinner than on the surface and usually infiltrated with T cell and dendritic cells

58
Q

Palatine tonsils contain numerous what?

A

lymphoid follicles containing B-cells;

spaces between the follicles represent the T cell regions and contain high-endothelial venules

59
Q

Where do lymphocytes exit the lymphoid tissue and join the bloodstream?

A

high endothelial venules

60
Q

Do palatine tonsils have a capsule?

A

partially encapsulated and separated from the underlying tissue by a thick CT capsule

61
Q

Where are pharyngeal tonsils located? What else are they called?

A

adenoids are located on the posterior aspect of the nasopharynx

62
Q

What is the epithelium of pharyngeal tonsils?

A

pseudostratified columnar epithelium

makes several folds, but does not have crypts

63
Q

What tonsils are found on the tongue?

A

lingual tonsils

64
Q

What tonsils are found inferior to the auditory tube?

A

tubal tonsils

65
Q

What are small bean shaped encapsulated lymphatic organs that filter lymph?

A

lymph nodes

66
Q

How does the lymph node receive and send out lymph?

A

concave area of the node contains the hilum, where the efferent lymphatic vessel exits the node and the blood vessels enter it

the convex part of the node receives lymph from the afferent lymphatic vessels

67
Q

Describe the capsule of lymph nodes

A

CT capsule

directly beneath is the subcapsular sinus space

the capsule forms projections into the parenchyma called trabeculae

trabeculae contain trabecular (or radial) sinuses within them

68
Q

The bulk of the tissue of the lymph nodes is formed of what?

A

reticular tissue rich in reticular (type III collagen) fibers, reticular cells (fibroblasts), lymphocytes, and dendritic cells/macrophages

69
Q

What is the cortex of lymph nodes like?

A

covers outer part except for hilum

consists of dense lymphatic tissue supported by a framework of reticular fibers synthesized by the specialized fibroblasts called reticulocytes

70
Q

What is cell organization in the outer cortex of the lymph node like?

A

lymphocytes in outer cortex are organized into lymphoid follicles and thus is the B cell region

71
Q

What is the inner cortex of the lymph nodes organized like?

A

inner cortex/paracortex are mostly T cells

contains a large number of high endothelial venules to allow emigration of T cells from blood into the lymph node

72
Q

What is the medulla of the lymph node like?

A

more loosely arranged cells than the cortex

composed of medullary cords surrounded by medullary sinuses

also supported by network of reticular fibers secreted by reticular cells

73
Q

medually cords contain

A

lymphocytes (mostly B cells), plasma cells, macrophages, dendritic cells, adn few T cells

74
Q

medually sinuses receive

A

lymph from trabecular sinuses and converge near the hilum, where they drain into the efferent lymphatic vessel

medually B cells can leave the node through the meduallary sinues to travel the body

75
Q

What do lymphatic sinuses do and contain?

A

allows for the filtration of lymph and provides channels

contain a meshwork of reticular fibers and macrophage processes that are designed to trap antigens and transformed cells (metastatic or infected) filtering the lymph

76
Q

What cells present in lymphatic sinuses secrete antibodies?

A

plasma cells

77
Q

What is the lymph flow through the lymph node pathway?

A
  1. afferent lymphatic vessels from convex area
  2. to the subcapsular sinus
  3. trabecular sinuses run through the CT within the cortex, drain lymph from the subcapsular sinus
  4. to the medullary sinuses among the medullary cords
  5. to the efferent lymphatic vessel leaving through the hilum
78
Q

What is blood flow through the lymph looking like?

A

artery supplying the LN breaks into the capillary bed within the cortex and the postcapillary venules are formed with the inner cortex (paracortex)

79
Q

What epithelium lines postcapillary venules in LNs? What are these also known as?

A

cuboidal

high endothelial venules

80
Q

How does lymph flow into the LNs?

A

express a high concentration of water channels (aquaporin-1)

allows rapid resorption of interstitial fluid via water channels into blood stream

causing lymph to be drawn into the node via afferent lymphatic vessels d/t solvent drag

81
Q

How do B and T cells gain entry to the LNs?

A

specialized endothelial cells of HEVs have receptors that signal both B and T cells to leave the circulation and migrate into the lymph node between endothelial cells

82
Q

Where do B and T cells once in the LNs?

A

T cells remain in the paracortex

B cells migrate to the outer cortex

83
Q

How do lymphocytes leave LNs?

A

most lymphocytes leave the LN by entering lymphatic sinuses from which they flow to an efferent lymphatic vessel

84
Q

What is the function of LNs?

A

important site for phagocytosis and initiation of immune response

85
Q

Increased concentration of antigens in the LN enhances what? What does this cause?

A

enhances the presentation to lymphocytes

leads to activation and differentiation of B cells into antibody producing plasma cells and memory B cells

86
Q

What do plasma cells do within LNs?

A

migrate to medullary cords where they synthesize and release specific antibodies into the lymph flowing through the sinuses

87
Q

What do memory B cells do upon leaving the LNs?

A

circulate to various regions throughout the body, proliferate in response to subsequent exposure to their specific antigen

88
Q

exit of the lymphocytes into the blood from lymphatic tissue goes through what?

A

cuboidal epithelium, high endothelial venules

89
Q

The majority of lymphocytes in the blood are….

A

T cells

90
Q

Where are HEVs usually found?

A

T cell regions of lymphoid tissues

91
Q

What is a B cell’s pathway to get out of the lymphoid tissue?

A

leaving through HEV, have to migrate through the T cell region, during which time they become activated, to reach the B cell region of the lymphoid tissue

92
Q

What does the spleen do?

A

filters blood and reacts immunologically to blood-borne antigens

93
Q

What does the capsule of the spleen contain? Why is this important?

A

dense CT capsule contains regular fibroblasts and myofibroblasts, allowing for the organ to contract, squeezing the blood out of it

trabeculae from the capsule dive into the parenchyma

94
Q

What does the spleen parenchyma contain?

A

white pulp - large number of WBCs

red pulp - high concentration of RBCs

95
Q

What are the two major components of white pulp?

A

periarterial lymphatic sheath (PALS) - mainly T cells surrounding central artery

lymphoid follicles - consist mainly of B cells, attached to the PALS

96
Q

What does the red pulp contain?

A

RBCs, splenic sinuses (dilated sinusoidal capillaries), splenic cords (cords of Billroth)

circulation within the red pulp allows macrophages to screen antigens in the blood

97
Q

What are splenic cords like?

A

resemble meduallary cords in having a dense meshwork of reticular fibers secreted by reticular cells

RBCs, macrophages, lymphocytes, plasma cells, and granulocytes reside within the meshwork

98
Q

Where are damaged RBCs phagocytized?

A

splenic macrophages

iron is recycled

99
Q

splenic sinuses receive blood from where?

A

blood that has been filtered through the cords

100
Q

How does blood get into the spleen? What surrounds these arteries?

A

splenic artery brings blood in and upon entering the capsule breaks into trabecular arteries, which are running through the CT trabeculae and are NOT surrounded by lymphocytes

101
Q

After exiting from the trabeculae the arteries develop…

A

a layer of T cells around them called the periarterial lymphatic sheath (PALS)

artery at this point is called central artery as it is located in the center of PALS

102
Q

What pulp is the central artery in?

A

white pulp, where PALS has a greater role

103
Q

As the central artery loses PALS, it enters

A

the red pulp and branches into several short straight vessels called penicillar arterioles

104
Q

Penicillar arterioles continue as small arterial capillaries which are surrounded by a sheath of

A

macrophages, and are thus called sheathed capillaries

105
Q

sheathed capillaries dump the blood…

this type of circulation is considered…

A

directly into the splenic cords

open circulation

106
Q

after ‘percolating’ through the cords, blood filters into…

A

splenic sinuses, which are dilated venous sinusoidal capillaries

107
Q

What is the endothelium lining sinuses in the spleen like?

A

endothelial cells are rod-shaped and contain gaps between individual cells allowing for RBCs to squeeze through the walls

do NOT have continuous basal lamina

108
Q

blood from the splenic sinuses is collected into the

A

pulp veins

109
Q

pulp veins deliver blood to the larger

A

trabecular veins located within the CT trabeculae

110
Q

trabecular veins eventually merge to form the

A

splenic vein, which exits organ via hilum

111
Q

What are the immune functions of the spleen?

A

antigen presentation by antigen-presenting cells and initiation of immune response

activation and proliferation of B and T lymphocytes

producation of antibodies against antigens present in circulating blood

removal of macromolecular antigens from the blood

112
Q

What are the blood maintenance/hemopoiesis functions of the spleen?

A

removal and destruction of senescent/damaged and abnormal RBCs and platelets (macrophages of red pulp)

retrieval of iron from RBC hgb

formation of RBC during early fetal life

113
Q

How is iron stored once retrieved by the spleen?

A

ferritin/hemosiderin

114
Q

Heme is broken into what by the spleen?

A

bilirubin

115
Q
A

HemeOnc Block (4 decks)

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