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Histo Block 4 > Lymphoid System > Flashcards

Lymphoid System Flashcards

(68 cards)

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1
Q

2 major types of lymphocytes?

A

B and T

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2
Q

Role of T lymphocytes?

A

involved in cell-mediated immunity

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3
Q

Role of B lymphocytes?

A

involved in humoral immunity; differentiate into plasma cells which secrete antibodies

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4
Q

What does recirculating mean?

A

traveling; lymphocytes travel through blood and lymphatic vessels between different sites of lymphoid tissues

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5
Q

What does immunocompetent mean?

A

have developed the ability to recognize and respond to a single, specific foreign antigen

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6
Q

What does recirculation ensure?

A

that the “right” lymphocytes will encounter and thereby destroy the “right” foreign antigens

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7
Q

Function of primary lymphoid organs?

A

place where lymphocytes differentiate into T and B cells

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8
Q

Function of secondary lymphoid organs?

A

where foreign antigens are captures and immune responses are mounted to trap and destroy those antigens

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9
Q

Where do T cells differentiate?

A

Thymus

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10
Q

Where do B cells differentiate?

A

Bone Marrow

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11
Q

Describe diffuse lymphatic tissue.

A

areas of loose CT where large numbers of lymphocytes and plasma cells are present

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12
Q

Where is diffuse lymphatic tissue found?

A

digestive tract, respiratory tract, urogenital tract

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13
Q

Describe isolated lymphatic nodules/follicles.

A

Discrete concentrations of lymphocytes contained in a meshwork of reticular cells

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14
Q

What are the 2 types of isolated lymphatic nodules?

A

primary and secondary

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15
Q

Describe primary lymphatic nodules.

A

oval accumulations of mostly small lymphocytes

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16
Q

Describe secondary lymphatic nodules.

A

Outer dark staining cortex/mantle containing densely packed lymphocytes with a lighter central germinal center with large lymphocytes, plasma cells, and macrophages

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17
Q

Where are aggregated lymphatic nodules found?

A

as Peyer’s patches in the ileum and also in the appendix

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18
Q

What type of lymphoid tissue constitutes about 85% of the body’s lymphoid tissue?

A

MALT

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19
Q

What does MALT mean?

A

mucosa associated lymphoid tissue

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20
Q

Function of tonsils?

A

capture and mount an immune response against antigens entering the body through the mouth and nose

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21
Q

3 kinds of tonsils?

A

palatine, pharyngeal, lingual

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22
Q

location of palatine tonsils?

A

the “tonsils” located on either side of pharynx

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23
Q

location of pharyngeal tonsils?

A

located at the roof of the pharynx

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24
Q

location of the lingual tonsils?

A

near the base of the tongue

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25
Describe the stroma of the palatine tonsils.
half capsule of dense, irregular CT; septa of dense, irregular CT; reticular cells/fibers
26
Describe the parenchyma of the palatine tonsils.
consists of lymphoid nodules and diffuse lymphoid tissue
27
Epithelium of palatine tonsils?
non-keratinized stratified squamous epithelium
28
How is palatine tonsil epithelium kept moist?
by secretions from mucous glands
29
Function of lymph nodes?
small encapsulated organs along the course of larger lymphatic vessels that trap and destroy foreign antigens and particulate matter in the lymph
30
Describe the stroma of lymph nodes.
capsule and septa/trabeculae of dense, irregular CT; reticular cells/fibers
31
What are the 2 components of the parenchyma of lymph nodes?
cortex and medulla
32
Describe structure of the lymph node cortex.
Outer cortex of lymphoid nodules and paracortex/deep cortex of dense lymphoid tissue
33
Describe structure of medulla of lymph nodes.
Medullary cords of B cells, plasma cells, and macrophages dispersed among medullary sinuses
34
Describe the flow of lymph.
Lymph enters afferent lymphatic vessels --> cortical (subcapsular) sinus --> trabecular sinuses --> medullary sinuses --> exits efferent lymphatic vessels
35
What can cause lymph node infections?
trapping of bacteria
36
What can cause metastasis to lymph nodes?
trapping of malignant cells
37
How do most lymphocytes enter lymph nodes?
via the blood supply
38
What type of cells line post-capillary venules in the paracortex and what is their function?
high cuboidal endothelial cells which express surface receptors that specifically recognize lymphocytes
39
How do lymphocytes exit the high endothelial venules?
by diapedesis and migrate to either the outer cortex and medullary cords (B cells) or the paracortex (T cells)
40
Where is the spleen located?
upper left abdomen
41
Describe the stroma of the spleen.
capsule of dense, irregular CT containing myofibroblasts and covered by mesothelium; septa/trabeculae of dense, irregular CT; reticular cells/fibers
42
Describe the parenchyma of the spleen.
islands of white pulp surrounded by red pulp
43
Where does the splenic artery enter the spleen?
at the hilus
44
What surrounds the central artery of the spleen?
white pulp
45
What does white pulp consist of?
PALS (periarterial lymphatic sheath) rich in T cells and splenic nodules
46
What does the red pulp consist of?
splenic cords (cords of Billroth) and splenic sinuses
47
Path of central artery?
leaves the white pulp and enters the red pulp where it branches into penicillar arterioles that continue as sheathed capillaries which end as terminal arterial capillaries
48
Spleen is open of closed system of circulation?
OPEN
49
Functions of the spleen?
trap and mount immune responses against antigens in the blood, remove and phagocytose damaged RBCS and platelets, retrieve iron from hemoglobin and store for later, hematopoiesis during fetal life
50
What happens to splenic functions if spleen is removed?
the bone marrow and liver will take over its role in removing damaged RBCs from circulation but these people will be more prone to infection
51
Location of thymus?
upper chest in front of heart
52
Does the thymus mount an immune response?
NO--primary lymphoid organ where T cells develop
53
Composition of thymus?
comprised of lobules, NOT lymphoid nodules/follicles
54
Describe stroma of thymus.
capsule of dense irregular CT; septa of dense, irregular CT; epithelioreticular cells
55
Function of epithelioreticular cells?
forms a continuous epithelium in early development but are later pushed apart by infiltrating lymphocytes; these cells have long processes that are joined together by desmosomes to form a supporting meshwork
56
Describe the parenchyma of the thymus.
Each lobule has an outer cortex and inner medulla
57
Describe the cortex of the thymus.
many small, densely packed T-cells, macrophages, epithelioreticular cells
58
Describe the medulla of the thymus.
less densely packed T cells, epithelioreticular cells, Hassall's corpuscles
59
What is the distinguishing feature of the thymus?
Hassall's corpuscles
60
Describe Hassall's corpuscles.
concentrically arranged epithelioreticular cells; show signs of keratinization and degeneration
61
What type of lymphoid organ is the thymus?
primary
62
Does the thymic cortex contain foreign antigens?
NO--it has a blood-thymic barrier
63
What are the 5 layers of the blood-thymic barrier?
endothelial cells joined by tight junctions, their basal lamina, perivascular CT w macrophages, basal lamina produced by epithelioreticular cells, epithelioreticular cells
64
What happens to T cells that recognize self antigens?
they are generated but are destined to die, phagocytosed by macrophages
65
Path of differentiated T cells in the thymus?
Differentiated T cells migrate from the cortex to the medulla and they later enter the blood supply by means of high endothelial venules; they then travel to "thymus-dependent" regions of secondary lymphoid organs
66
What happens to the thymus at puberty?
it begins to involute and be replaced by fat cells
67
What happens if the thymus is removed early in development?
it leads to impaired cell-mediated immunity
68
What is the distinguishing feature of the spleen?
central artery

Histo Block 4 (3 decks)

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