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Histo Block 4 > Lymphoid System > Flashcards

Lymphoid System Flashcards

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
Q

Describe the stroma of the palatine tonsils.

A

half capsule of dense, irregular CT; septa of dense, irregular CT; reticular cells/fibers

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26
Q

Describe the parenchyma of the palatine tonsils.

A

consists of lymphoid nodules and diffuse lymphoid tissue

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27
Q

Epithelium of palatine tonsils?

A

non-keratinized stratified squamous epithelium

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28
Q

How is palatine tonsil epithelium kept moist?

A

by secretions from mucous glands

29
Q

Function of lymph nodes?

A

small encapsulated organs along the course of larger lymphatic vessels that trap and destroy foreign antigens and particulate matter in the lymph

30
Q

Describe the stroma of lymph nodes.

A

capsule and septa/trabeculae of dense, irregular CT; reticular cells/fibers

31
Q

What are the 2 components of the parenchyma of lymph nodes?

A

cortex and medulla

32
Q

Describe structure of the lymph node cortex.

A

Outer cortex of lymphoid nodules and paracortex/deep cortex of dense lymphoid tissue

33
Q

Describe structure of medulla of lymph nodes.

A

Medullary cords of B cells, plasma cells, and macrophages dispersed among medullary sinuses

34
Q

Describe the flow of lymph.

A

Lymph enters afferent lymphatic vessels –> cortical (subcapsular) sinus –> trabecular sinuses –> medullary sinuses –> exits efferent lymphatic vessels

35
Q

What can cause lymph node infections?

A

trapping of bacteria

36
Q

What can cause metastasis to lymph nodes?

A

trapping of malignant cells

37
Q

How do most lymphocytes enter lymph nodes?

A

via the blood supply

38
Q

What type of cells line post-capillary venules in the paracortex and what is their function?

A

high cuboidal endothelial cells which express surface receptors that specifically recognize lymphocytes

39
Q

How do lymphocytes exit the high endothelial venules?

A

by diapedesis and migrate to either the outer cortex and medullary cords (B cells) or the paracortex (T cells)

40
Q

Where is the spleen located?

A

upper left abdomen

41
Q

Describe the stroma of the spleen.

A

capsule of dense, irregular CT containing myofibroblasts and covered by mesothelium; septa/trabeculae of dense, irregular CT; reticular cells/fibers

42
Q

Describe the parenchyma of the spleen.

A

islands of white pulp surrounded by red pulp

43
Q

Where does the splenic artery enter the spleen?

A

at the hilus

44
Q

What surrounds the central artery of the spleen?

A

white pulp

45
Q

What does white pulp consist of?

A

PALS (periarterial lymphatic sheath) rich in T cells and splenic nodules

46
Q

What does the red pulp consist of?

A

splenic cords (cords of Billroth) and splenic sinuses

47
Q

Path of central artery?

A

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
Q

Spleen is open of closed system of circulation?

A

OPEN

49
Q

Functions of the spleen?

A

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
Q

What happens to splenic functions if spleen is removed?

A

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
Q

Location of thymus?

A

upper chest in front of heart

52
Q

Does the thymus mount an immune response?

A

NO–primary lymphoid organ where T cells develop

53
Q

Composition of thymus?

A

comprised of lobules, NOT lymphoid nodules/follicles

54
Q

Describe stroma of thymus.

A

capsule of dense irregular CT; septa of dense, irregular CT; epithelioreticular cells

55
Q

Function of epithelioreticular cells?

A

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
Q

Describe the parenchyma of the thymus.

A

Each lobule has an outer cortex and inner medulla

57
Q

Describe the cortex of the thymus.

A

many small, densely packed T-cells, macrophages, epithelioreticular cells

58
Q

Describe the medulla of the thymus.

A

less densely packed T cells, epithelioreticular cells, Hassall’s corpuscles

59
Q

What is the distinguishing feature of the thymus?

A

Hassall’s corpuscles

60
Q

Describe Hassall’s corpuscles.

A

concentrically arranged epithelioreticular cells; show signs of keratinization and degeneration

61
Q

What type of lymphoid organ is the thymus?

A

primary

62
Q

Does the thymic cortex contain foreign antigens?

A

NO–it has a blood-thymic barrier

63
Q

What are the 5 layers of the blood-thymic barrier?

A

endothelial cells joined by tight junctions, their basal lamina, perivascular CT w macrophages, basal lamina produced by epithelioreticular cells, epithelioreticular cells

64
Q

What happens to T cells that recognize self antigens?

A

they are generated but are destined to die, phagocytosed by macrophages

65
Q

Path of differentiated T cells in the thymus?

A

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
Q

What happens to the thymus at puberty?

A

it begins to involute and be replaced by fat cells

67
Q

What happens if the thymus is removed early in development?

A

it leads to impaired cell-mediated immunity

68
Q

What is the distinguishing feature of the spleen?

A

central artery

Histo Block 4 (3 decks)

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