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Tissue Biology > Histology of the Lymphoreticular System > Flashcards

Histology of the Lymphoreticular System Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the organs of the lymphoreticular system?

A

Thymus, lymph node, mucosa-associated lymphoid tissue (MALT), spleen

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2
Q

The immune system provides highly specific responses to what specifically?

A

To antigens with the destruction of the antigen

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3
Q

What was the original definition of an antigen?

A

Any molecule that binds specifically to an antibody

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4
Q

What does the term antigen now also refer to?

A

Any molecule or molecular fragment that can be bound by a major histocompatability complex (MHC) and presented to a T helper cell

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5
Q

What is the function of a MHC - major histocompatability complex?

A

The function of MHC molecules is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells.

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6
Q

What are the the types of lymphocytes?

A

B lymphocytes and t lymphocytes

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7
Q

What is the function of the b lymphocytes?

A

To produce antibodies

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8
Q

What is the function of the t lymphocytes?

A

They have several subtypes and act as suppressor cells, cytotoxic cells and helper cells

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9
Q

What are antigen presenting cells?

A

They include macrophages and the b lymphocytes control the activation of the t cells. An antigen-presenting cell is a cell that displays antigen complexed with major histocompatibility complexes (MHCs) on their surfaces

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10
Q

Why are the b lymphocytes called b lymphocytes?

A

Because they are formed from a stem cell, into a pre-b cell and the pre-b cell matures into a fully functional b cell in the red bone marrow

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11
Q

Why are the t lymphocytes called t lymphocytes?

A

Because they are formed from a stem cell into a pre t cell in the red bone marrow. but then the pre-t cell matures into a fully functional t cell in the thymus

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12
Q

Roughly what percentage of white blood cells in circulation are lymphocytes?

A

20-50%

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13
Q

The number of lymphocytes in circulation increase in response to what?

A

In response to a viral infection

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14
Q

How would you describe lymphocytes under a microscope

A

they have a round/oval nuclei with dense chromatin and nucleoli which are not usually visible and often very little cytoplasm

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15
Q

How does the size of a lymphocyte compare to the size of red blood cells?

A

red blood cells are about 7 microns in diameter - about the size of a lymphocyte nucleus

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16
Q

What are the two types of lymphocytes?

A

t and b

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17
Q

what are the three types of t lymphocyte?

A

t helper cells, cytotoxic t cells and suppressor t cells

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18
Q

what do t helper cells do

A

they help other lymphocytes perform functions

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19
Q

what do cytotoxic t cells do

A

they kill virally infected and malignant cells

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20
Q

what do suppressor t cells do

A

they switch off the immune system when the stimulating antigen is removed

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21
Q

what do b lymphocytes do

A

they produce antibodies following maturation to plasma cells

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22
Q

what is a plasma cell

A

a fully differentiated B-lymphocyte (white blood cell) which produces a single type of antibody.

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23
Q

what types of cells are included in the antigen presenting cells category

A

macrophage monocyte type cells and dendritic cells

24
Q

what do antigen presenting cells do?

A

the antigen is taken up by the apc and processed. processed antigen is then bound to a major histocompatability complex and the mhc-peptide complex is exposed to the outside world

25
Q

how would you describe the dendritic cell morphology

A

finger like projections

26
Q

what are the four organs of the lymphoid system

A

thymus, lymph nodes, mucosa-associated lymphoid tissue, spleen

27
Q

what is the thymus

A

a flattened lymphoid organ

28
Q

where is the thymus located

A

in the upper anterior mediastinum and lower part of the neck

29
Q

when is the thymus most active and when does it undergo involution

A

most active during childhood, heaviest at puberty and then undergoes involution

30
Q

what does the thymus consist of

A

its got a right and left lobe, its got septae and its made of lobules

31
Q

what function does the thymus have in terms of t lymphocytes

A

the thymus is involved in the development of immunocompetent t lymphocytes from t cell precursors derived from bone marrow

32
Q

what types of hormones would the thymus release

A

secretion of hormones which regulate t cell maturation, proliferation and function

33
Q

why does the thymus allow the proliferation of clones of mature naive t cells

A

to supply the lymphocyte pool

34
Q

what does the thymus originate as

A

the thymus originates as epithelial outgrowths which merge in the midline forming an organ with fine lobules

35
Q

the epithelium originally forming the thymus develops into what to house what

A

the epithelium develops into a sponge like structure containing numerous interconnecting spaces which are colonised by immature t cells

36
Q

what is in the centre of the epithelial meshwork making up the thmus

A

in the centre the epithelial meshwork is coarser with a smaller lymphocyte population so the gland has an outer cortex and a less cellular central medulla

37
Q

*label this thymus

A

there

38
Q

what do the epithelial cells provide the thymus with

A

a strong mechanical framework

39
Q

what is the function of the cortical epithelial cells / nurse cells

A

they enevelope multiple lymphocytes promoting t cell differentiation and proliferation

40
Q

what forms hassal’s corpuscles

A

groups of keratinised epithelial cells

41
Q

are hassal’s corpuscles eosinophillic or basophillic

A

eosiophilic structures

42
Q

what are APC cells in the thymus called

A

thymic interdigitating cell

43
Q

in adults where do the t cell precursors enter

A

at the cortico-medullary junction

44
Q

once the t-cell precursors have entered the thymic cortico-medullary junction what happens

A

they begin a highly ordered differentiation programme which is linked to migration through the thymic stroma

45
Q

where are mature lymph nodes found

A

distributed throughout the body in aggregates, present along the larger regional vessels of the lymphovascular system

46
Q

lymph nodes occur in groups, give some examples

A

neck, axillae, groins, lung hila and para-aortic areas

47
Q

list four functions of the lymph nodes

A
  1. non specific filtration of particulate matter and micro organisms from lymph
  2. interaction of circulating lymphocytes with antigen containing lymph
  3. activation and proliferation of b cells
  4. aggregation, activation and proliferation of t cells
48
Q

*label this lymph node

A

there ya go

49
Q

what three types of cells are present in lymph nodes

A

lymphoid cells, immunological accessory cells and stromal cells

50
Q

how would you describe the lymph node and the function of lymph nodes

A

small bean shaped organs situated on the course of lymphatics so lymph draining back to bloodstream passes through one or more lymph nodes

51
Q

in the inactive state what is the size of a lymph node

A

only a few mm in size

52
Q

what is the outer and central area of a lymph node described as

A

the outer part is highly cellular and called the cortex

the central area is less cellular, called the medulla

53
Q

what is a lymph node surroudned by

A

a collagenous capsule from which trabeculae extend for a variable distance into the node

54
Q

what do afferent lymphatic vessels divide into and where

A

they divide into branches outside the node and pierce the capsule to drain into a narrow space

55
Q

when the afferent lymphatic vessels divide into branches outside the node and pierce the capsule to drain into a narrow space, what is this narrow space called?

A

the subcapsular sinus which encircles the lymph node beneath the capsule

Tissue Biology (16 decks)

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