Lymphoid Tissue and Organs Flashcards
1
Q
What is our body’s immune/defense system?
A
cells, tissues, and organs that protect our body from antigens, pathogens, bacteria and viruses
2
Q
What type of cells do lymphatic tissues contain?
A
lymphocytes
3
Q
What are the two types of lymphocytes?
A
T and B lymphocytes
4
Q
What are the two classifications on lymphatic tissues?
A
primary and secondary
5
Q
What are the two kinds of primary lymphatic tissues?
A
1) bone marrow
2) thymus
6
Q
What is the function of primary lymphatic tissues?
A
1) they are the site of development and maturation for lymphocytes to become immunocompetent cells (immune school)
2) they provide these immunocompetent cells to secondary lymphatic tissues
7
Q
What are the three kinds of secondary lymphatic tissues?
A
1) lymph nodes
2) MALT (mucosa-associated lymphatic tissue)
3) spleen
8
Q
What is the function of lymph nodes?
A
filter lymph
9
Q
What’s the function of MALT?
A
surveillance
10
Q
What’s the function of the spleen?
A
filters blood
11
Q
What is the largest lymphatic organ?
A
spleen
12
Q
What are the 4 varieties of MALT?
A
1) GALT (gut-associated lymphatic tissue)
2) BALT (bronchus-associated lymphatic tissue)
3) GU (genitourinary) tract
4) tonsils
13
Q
Where is GALT located?
A
lamina propria of GI tract
14
Q
Where is BALT located?
A
lamina propria of respiratory tract (ie bronchi)
15
Q
What’s the function of secondary lymphatic tissues?
A
1) battlefield against antigens and pathogens (immunological defense)
2) confrontation with antigens or pathogens occurs here
16
Q
What is lamina propria?
A
1) Latin for first layer
2) loose connective tissue just inside the epithelium
17
Q
How are lymphatic tissue present in lamina propria?
A
they are usually in clusters found in lamina propria. As pathogens invade through the epithelium, the lymphocytes in the area mount an attack on the invading pathogens
18
Q
What are the different cell types found in lymphatic tissue?
A
1) lymphocytes
2) monocytes
3) macrophages
4) plasma cells
19
Q
What are lymphatic nodules? What are the two types?
A
they are like lymphatic tissues but more complex. there are primary and secondary lymphatic nodules, based entirely on appearance
20
Q
Presence of secondary nodules are indicative of what?
A
an immune response is occuring
21
Q
A secondary nodule has which two distinctive areas that can be seen with light microscope?
A
Mantle zone and germinal center
22
Q
What type of lymphocytes does mantle zone contain?
A
small mature lymphocytes
23
Q
What type of lymphocytes does germinal center contain?
A
medium and large lymphocytes
24
Q
What appearance does mantle zone of a secondary lymphatic nodule will have in a micrograph?
A
dark ring that surrounds the germinal center. dark due to the large number of small nuclei per area
25
What appearance does germinal center of a secondary lymphatic nodule will have in a micrograph?
lighter in color and located in the center. this is an area where lots of mitosis and proliferation are occurring
26
What are temporary lymphatic nodules called?
solitary lymphatic nodules
27
What are permanent lymphatic nodules called?
aggregates of lymphatic nodules
28
What are some examples of permanent lymphatic nodules (6)?
1) Peyer's patches in the ileum
2) lymphatic tissue in the appendix
3) BALT
4) tonsils
5) lymph nodes
6) spleen
29
Lymphatic nodules are seen in the wall of the colon, are they temporary or permanent?
they are solitary lymphatic nodules so temporary
30
Are lymphatic tissues in the appendix temporary or permanent?
permanent; they are an example of lymphatic nodule aggregates
31
What type of lymphatic nodules are tonsils?
permanent, aggregates of lymphatic nodules
32
What type of lymphocytes are in tonsils?
B lymphocytes
33
What are the three major types of tonsils?
1) pharyngeal tonsil (adenoid)
2) palatine tonssils
3) lingual tonsils
34
Where is pharyngeal tonsil located?
wall of the nasopharynx
35
What type of epithelium does pharyngeal tonsil have?
ciliated pseudostratified columnar epithelium (respiratory)
36
Where can you find palatine tonsils?
in the oropharynx, on either side (say "uh")
37
Where can find lingual tonsils?
bumps found on the posterior/dorsal portion of the tongue
38
What type of epithelium do lingual tonsils have?
stratified squamous, non-keratinized
39
Briefly describe the epithelium of palatine tonsils
infiltrated by many B lymphocytes and dives into crypts
40
What are crypts?
they are spaces or fissures that may may contain bacteria or food particles, also lined with the same epithelium
41
Describe the cap of palatine tonsils
dense irregular collagenous connective tissue that partially surrounds the basilar region of the tonsil (like a cup or basket)
42
If you see two distinctive areas of in a lymphatic nodule, what type is it?
secondary, the two distinctive areas are mantle zone and germinal center
primary lymphatic nodules are homogenous in appearance
43
What is lymph?
excessive tissue fluid from the vascular system
44
Where are lymph nodes found?
along the path of lymphatic vessels
45
Briefly describe the capsule of a lymph node
thin layer of dense irregular collagenous connective tissue
46
What are trabeculae of a lymph node?
capsule extensions inward as septal processes
47
What carries blood vessels and nerve fibers into the lymph node?
trabeculae
48
What are the two distinctive regions of lymph nodes?
1) cortex (periphery)
| 2) medulla (core)
49
What are the two different surfaces of a lymph node?
1) convex (top of a dome)
| 2) concave
50
Where are afferent lymph vessels located?
convex surface of a lymph node, they have valves that can control flow
51
Describe the flow of lymph through a lymph node
afferent lymph vessel >> subcapsular sinus >> trabecular sinus >> medullary sinus >> efferent lymph vessel
52
What is the hilum and where is it found?
space where vessels enter/exit the lymph node. it is located in the concave surface of lymph node
53
What three vessels are found at the hilum?
1) artery
2) vein
3) efferent lymph vessel
54
Where are subcapsular sinuses located?
just underneath the capsule
55
Where are trabecular sinuses located?
surrounds the trabeculae, separates the connective tissue of the trabeculae from the lymphatic tissue of cortex
56
Where are medullary sinuses located?
inside the medulla
57
Where is the paracortex located?
it's also known as deep cortex, located just above the medulla
58
What's the function of reticular fibers in a lymph node?
they create a 3D meshwork that helps suspend cells and sinuses; prevents the looser lymphatic tissue from collapsing
59
What does the 3D reticular tissue consist of (5)?
1) reticular cells and fibers
2) dendritic cells
3) macrophages
4) plasma cells
5) follicular dendritic cells
60
What do reticular cell have that cover the surface of the reticular fibers to isolate them from surrounding lymphatic tissue?
cytoplasmic processes
61
What's the purpose of dendritic cells and macrophages?
they are antigen-presenting cells
62
What are follicular dendritic cells?
they have processes that are situated between lymphocytes and they bind to antigen/antibody complexes
63
What does parenchyma mean?
cellular part
64
What type of lymphocytes are located in lymphatic nodules (follicles) of the cortex?
B lymphocytes
65
What type of lymphocytes are located in the paracortex (deep cortex)?
T lymphocytes
66
What can you find in the cortex of a lymph node?
secondary lymphatic nodules (meaning there are two regions - mantle zone and germinal center)
67
What are medullary cords?
irregular clumps of B lymphocytes, monocytes, macrophages, plasma cells
68
What is the function of medullary sinuses?
final area for lymph to collect and where pathogens can be removed.
69
High endothelial venules (HEVs) are found in which layer of the lymph nodes?
paracortex
70
What is different about HEVs versus regular endothelial cells that normally line vessels?
HEVs are made up of different type of epithelium. these are cuboidal epithelium instead of squamous. because they are taller, they are named "high" endothelial venules
71
Where do majority of lymphocytes enter the lymph node?
via HEVs in the paracortex (90% of lymphocytes)
| the other 10% enter via afferent lymph vessels
72
Once the lymphocytes exit the lumen of HEV, where do they go?
B lymphocytes migrate to the cortex
| T lymphocytes remain in the paracortex
73
What type of collagen are reticular fibers?
type III
74
Where do T lymphocytes mature? Is that where they originate?
thymus, no, they originated from bone marrow (BM)
75
Describe the path a young T lymphocyte
originate from BM, travel via bloodstream to the thymus where they go to school to become immunocompetent T cells.
they start out in the cortex of the thymus, then they mature in the medulla where they graduate and leave to do bigger and better things (like killing pathogens)
76
Where in the thymus would you find the most immature T cells?
most immature will be found in the outer layer; they mature as they move closer to the medulla
77
Where in the thymus would you find mature T cells?
medulla
78
Where do mature T cells get distributed to once they leave the medulla of they thymus (4)?
1) paracortex of lymph nodes
2) periarterial lymphatic sheath of the spleen
3) BALT
4) GALT
79
What are the five things that you won't find in a thymus but will in a lymph node?
The thymus DO NOT contain these:
1) afferent lymphatic vessels
2) 3D reticular fiber framework
3) lymphatic nodules
4) B lymphocytes
5) sinuses or sinusoids
80
What makes up the blood-thymus barrier (4)?
the capillaries are surrounded by the following layers:
1) cortical capillary endothelium
2) basal lamina
3) macrophages
4) type I epithelioreticular cells
81
What's the function of blood-thymus barrier?
isolates the developing T lymphocytes of the cortex from macromolecules circulating in the blood
82
What type of epithelium is cortical capillary endothelium?
```
simple squamous (typical endothelial cells)
continuous type, impermeable to many substances
```
83
How many types of epithelioreticular cells are there?
6
| **Note: types I,II, III are in the cortex. types IV, V, VI are in the medulla
84
Which type of epithelioreticular cells forms a layer over blood vessels which isolates T lymphocytes from overlaying CT?
type I
85
Which type of epithelioreticular cells isolates the cortex from the medulla?
type III
86
Which type of epithelioreticular cells forms a 3D reticulum with their cell processes to suspend T lymphocytes in the cortex?
type II
87
Which type of epithelioreticular cells are similar to type II and forms a 3D reticulum with their cell processes to suspend T lymphocytes in the medulla?
type V
88
Which type of epithelioreticular cells are similar to type II and are found at corticomedullary junction, isolating cortex from medulla?
type IV
89
Which type of epithelioreticular cells are a special type known as Hassall's corpuscles?
type VI
90
Where are Hassall's corpuscles found?
medulla of thymus
| **unique to thymus
91
What is the overall function of the epithelioreticular cells of the cortex?
protect, guard and create an antigen-free environment for the maturing lymphocytes residing in the cortex
92
What is DiGeorge's syndrome?
developmental disorder that is characterized by thymic hypoplasia or aplasia, cannot produce T lymphocytes to fight infections leading to death
93
Which pharyngeal pouch does the thymus develop from?
3rd
94
Where do B and T lymphocytes proliferate?
spleen
95
The parenchyma of spleen is divided into which two regions?
1) red pulp
| 2) white pulp
96
Which is more abundant, red or white pulp?
red pulp is more abundant, the "sea"; white pulp are the "islands" found in the sea
97
Does the spleen have a 3D framework of reticular fibers?
yes, they suspend the red pulp and sinuses
98
What do the sinuses in the spleen contain?
RBCs
99
What are the Cords of Billroth?
rows of cells in spleen (red pulp cord), contains macrophages
100
What colors will white and red pulp be if stained with hematoxylin and esoin?
White pulp will stain blue (from hematoxylin)
| Red pulp will stain red (from eosin)
101
What are the two regions of white pulp?
1) PALS (periarterial lymphatic sheath)
| 2) Splenic nodule (Malpighian corpuscle)
102
What can be found in red pulp?
1) splenic cords (of Billroth)
| 2) sinusoids
103
Where will you find T lymphocytes within white pulp?
PALS
104
Where will you find B lymphocytes within white pulp?
splenic nodules (Malpighian corpuscle)
105
The central artery of the spleen pass through which structure?
PALS
106
How is PALS formed?
the tunica adventitia of trabeculae is infiltrated by T lymphocytes, forming a sheath around the central artery
107
Once PALS loses its lymphatic sheath, it gives rise to what structure?
penicillar arterioles, which pass into the red pulp
108
Arterial capillaries are continuation of what?
penicillar arterioles
109
What are sheathed capillaries?
arterial capillaries that are covered by a sheath of macrophages
110
Where do blood empty into from sheathed capillaries?
splenic cords (of Billroth), blood is filtered here
111
Where do blood go after the splenic cords?
splenic sinuses
112
Where do blood go after the splenic sinuses?
general circulation
113
At what structure does the splenic artery enter the spleen and gives rise to multiple branches (trabecular arteries)?
hilum
