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Tissue biology > Week 6: The lymphoreticular system > Flashcards

Week 6: The lymphoreticular system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the MPS and what cells are in it?

A

Mononuclear phagocytic system.
monocytes, macrophages, and dendritic cells

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2
Q

From what cells are the lymphoreticular system derived from?

A

White blood cells

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3
Q

What are the two groups from which the lymphoreticular system derive from?

A

Lymphoid cells (B and T lymphocytes)
Phagocytes (neutrophils, eosinophils) and the MPS

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4
Q

The haematopoietic cell differentiates into which two cells?

A

common myeloid and lymphoid

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5
Q

What cells do myeloblasts form?

A

Derived from the common myeloid progenitor they form:
-monocytes
-eosibophils
-basophils
-neutrophils

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6
Q

Where does haematopoiesis occur?

A

In the medulla of the bone marrow

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7
Q

What other progenitor cell is found in the bone marrow?

A

Megakaryocytes - progenitor cells for platelets

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8
Q

Where do immature T cells originate from and where do they travel?

A

Bone marrow -> thymus

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9
Q

Into what cells do T cells differentiate to?

A

T helper cells- help B cells and APCs
T killer (cytotoxic) - kill viruses etc.
T regulatory - suppress the immune response

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10
Q

How are T helper and T killer cells characterised?

A

T helper- surface protein CD4
T killer- surface protein CD8

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11
Q

Where do B lymphocytes mature?

A

In the bone marrow

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12
Q

What cells do B cells differentiate into?

A

Plasma cells or B memory cells

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13
Q

What is the function of a monocyte?

A

To ingest microorganisms, cell debris (phagocytic cells)

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14
Q

Where and what do monocytes differentiate into?

A

In the tissue to macrophages

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15
Q

Name the 4 types of macrophages in the body

A

Osteoclasts - bone resorption and remodelling
Kupffer cell - found in the liver
Microglia- found in the brain
Langerhan cell - APC in the skin

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16
Q

What is the function of a dendritic cell?

A

To process antigenic material and present it to the cell surface to a T cell

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17
Q

Where are the dendritic cells found?

A

Found in tissues in contact with the external environment such as the skin (Langerhans’s cells)

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18
Q

What are the two common immune responses

A

Innate immune response and the adaptive immune response

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19
Q

What occurs in the innate immune response

A

-MPS and granulocytes are activated
-Protein components (e.g. interleukins)
-Inflammation
-Cells support the adaptive system

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20
Q

Where is the thymus located?

A

It is a flattened lymphoid organ located in the base of the neck

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21
Q

What are the functions of the thymus?

A

-Development of T cells from bone marrow
-Apoptosis of T cells
-Secretion of hormones to regulate t cells

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22
Q

How is the thymus organised?

A

Into lobules with an outer cortex and an inner medulla

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23
Q

What is the difference between the adult and infant thymus?

A

In the mature thymus the lymphoid tissue is separated by adipose tissue

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24
Q

Where do immature T cells enter in the thymus?

A

In the cortico-medullary junction

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25
Q

What happens in the outer cortex of the thymus?

A

Large lymphoblasts divide to produce clones of smaller mature T cells

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26
Q

What type of selection of T cells occurs first?

A

Positive selection- only the T cells which recognise the MHC molecules continue to divide and mature

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27
Q

What selection occurs last and where?

A

In the medulla of the thymus, negative selection - any T cell with recognising self-antigens on the APC will be deleted (only those who don’t recognise a self antigen live)

28
Q

As T cells mature where do they migrate towards?

A

From the cortex to the medulla

29
Q

What 2 cells are found in the medulla of the thymus?

A

Hassall corpuscles and thymic interdigitating cells

30
Q

What are Hassall corpuscles?

A

A group of keratinised cells (thought to be degeneratifve)

31
Q

What are thymic interdigitating cells>

A

Dendritic cells that play a role in clonal deletion ( negative selection)

32
Q

What are the functions of lymph nodes?

A

-Filtration of lymphatic fluid for antigens
-Antigen processing
-Bring together antigen and APCs to facilitate immune response
-Activation of B and T lymphocytes
-B cells mature into plasma cells

33
Q

How does the structure of lymph nodes allow it to perform its function?

A

-Sieve for lymphatic fluid (cortical inuses)
-Many APCs for antigen presentation
-Highly vascular

34
Q

Describe the structure of the lymph nodes

A

Organised in a reticular network enclosed by a capsule (fibrous tissue), within the cortex there are follicles (primary follicles contain purely resting B cells)
Secondary B cells - are active

35
Q

Why do secondary B cells look paler on H&E stain>

A

Because they are actively transcribing DNA so the DNA is less tightly wound. Therefore they look paler

36
Q

Where are T cells activated>

A

In the paracortical area (deep into the cortex)

37
Q

Where does the afferent sinus lymph drain into?

A

The sub-capsular sinus

38
Q

Where are immature B cells contained?

A

Paler Germinal centre surrounded by a darker mantle zone (resting B cells) above that is the Marginal zone (paler)

39
Q

Where do naive/immature B cells enter the LN?

A

Via high endothelial venules from the blood supply

40
Q

Once in the LN what do immature B cells do?

A

Encounter an APC and macrophage and interact with the antigen. Undergo blast transformation

41
Q

Outline the steps of blast transformation

A
  1. In the dark zone of the GC (form the central blast)
  2. Move into the light zone of the GC and differentiate into centrocytes
  3. Centrocytes differentiate into either memory or plasma cells
42
Q

Where are centroblasts vs centrocytes found?

A

CB- In the darker zone closer to the medulla of the follicle
CC- paler zone of the GC towards the capsule

43
Q

What are FDC

A

Follicular dendritic cells, they are the main APCs in LN follicles

44
Q

What occurs in the paracortex?

A

T cell activation, they transform into larger immunoblasts (which divide into clones of T cells)

45
Q

What are the main APCs in the paracortex>

A

Interdigitating dendritic cells

46
Q

In the lymph node medulla how are branching medullary cords separated?

A

By irregular medullary sinuses

47
Q

Where do B cells complete their maturation?

A

In the medullary cords

48
Q

What is MALT?

A

Mucosa-associated lymphoid tissue ( lymphoid tissue distributed throughout the body at mucosal surfaces)

49
Q

What makes up MALT?

A

GI tract (tonsils)
Lamina propria of the gut and respiratory tract
Peyers patches of the SI

50
Q

How are the tonsils structured?

A

Organised in masses of lymphoid tissue forming the Waldeyer’s ring

51
Q

How is tonsil tissue different and similar to lymphatic tissue?

A

-Contains lymphoid follicals and GC
-There are tonsillar crypts

52
Q

What are Peyer’s patches?

A

Aggregated lymphoid follicles in the SI

53
Q

Where is the spleen located?

A

Left upper abdomen

54
Q

What kind of tissue makes the splenic tissue?

A

Red pulp and white pulp

55
Q

What are the functions of the spleen?

A

Production of immune response
Removal of old cells (RBCS)
Recycling iron to the bone marrow
Haematopoiesis

56
Q

How does the structure of the spleen allow it to perform its function?

A

Highly vascular rep pulp to filter antigens from blood
White pulp (B and T cells)
Contains many macrophages `

57
Q

What is the spleen encapsulated by?

A

A capsule

58
Q

What are trabeculae?

A

They form a path of branches of the splenic artery, from which smaller central arteries branch off to enter the splenic tissue

59
Q

What are the differences between red and white pulp?

A

RP- highly vascular (bulk of tissue)
WP- lymphoid aggregates
- Consists of B cells and mainly T cells which surround the central arteries

60
Q

What is PALS

A

periarteriolar lymphoid sheath
- are a portion of the white pulp of the spleen. They are populated largely by T cells and surround central arteries within the spleen;

61
Q

Where are B cells in the white pulp

A

In follicles at the edges of PALS/central arteries

62
Q

What are sheathed capillaries surrounded by?

A

Macrophages

63
Q

What is RP made of?

A

Macrophages and BC - removes old RBCs

64
Q

The sinuses in the RP are lined by what?

A

Endothelial cells (large SA where blood is in contact with the splenic tissue)

65
Q

What marker characterises B cells?

A

C20

66
Q

What marker characterises T cells?

A

CD4

67
Q

What marker characterises cytotoxin cells?

A

CD8

Tissue biology (4 decks)

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