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Immunity and infection > Anatomy > Flashcards

Anatomy Flashcards

1
Q

Location of the thymus

A

In the superior mediastinum (and anterior until puberty)
Posterior to the sternum
Anterior to the pericardium

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2
Q

What happens to the thymus after puberty

A

Undergoes involution

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3
Q

Parts of the thymus gland

A

Cortex

Medulla

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4
Q

In the thymus, is the cortex or medulla more cellular

A

Cortex is more cellular

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5
Q

What cells are in the thymus

A

Lymphoid cells
Macrophages
Epithelial cells
Supporting cells

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6
Q

How do epithelial cells in the thymus differ depending on location

A

In the cortex and outer medulla they form a continuous layer

In the deep medulla they are aggregated into Hassall’s corpuscles

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7
Q

Describe T cell maturation

A

Immature T cells from bone marrow enters the thymus cortex and proliferate, mature and then move into the thymus medulla
From the medulla, mature T cells enter the circulation

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8
Q

What is the lymphatic system

A

An ‘overflow system ‘ which:
Provides for the drainage of surplus tissue fluid and leaked plasma proteins into the bloodstream
Removes debris from cellular decomposition and infection

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9
Q

What are lymphatic plexuses

A

Network of lymphatic capillaries that originate from the extracellular spaces of most tissue

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10
Q

Where are blood capillaries found but not lymphatic capillaries

A

Teeth
Bone
Bone marrow
CNS

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11
Q

Features of lymphatic vessels

A

Thin walls

Abundant lymphatic valves

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12
Q

What are lymphoid organs

Give some examples

A 
Organs that produce lymphocytes, for example:
Thymus
Red bone marrow
Spleen 
Tonsils
GALT (gut associated lymphoid tissue)
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13
Q

Describe direction of lymphatic drainage

A

Superficial lymph nodes drain into deep lymph nodes
Deep lymph nodes join to form lymphatic trunks
Lymphatic trunks join to form the right lymphatic duct (right) or the thoracic duct (left)

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14
Q

What does the right lymphatic duct drain into

A

Right venous angle - junction of right subclavian and right internal jugular veins

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15
Q

What does the thoracic duct drain into

A

Left venous angle - junction of left subclavian and left internal jugular veins

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16
Q

Main functions of lymph nodes

A

Filter for particulate matter and microorganisms (phagocytic cells in nodes)
Present antigens to the immune system

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17
Q

Structure of lymph nodes

A 
Fibrous capsule which have extensions called trabeculae 
3 components are:
Lymphatic sinuses
Blood vessels
Parenchyma
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18
Q

What can the lymph node parenchyma be divided into

A

Cortex
Paracortex
Medulla

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19
Q

How do B cells enter lymph nodes and what do they pass into

A

Via post capillary venules called high endothelial venules (HEV)
B cells are passed to follicles of the lymph node

20
Q

What happens to B cells from the circulation if they are not stimulated in the lymph node

A

Rapidly return to the circulation with the lymph

21
Q

What happens to B cells from the circulation if they are stimulated by antigenic material in the lymph node

A

They remain in the node, proliferate and undergo somatic hypermutation
High affinity antibodies to the antigen are selected for by follicular dendritic cells
Stimulated B cells then take up the antigen, process it and present it to T cells

22
Q

What are stimulated B cells within lymphoid follicles called

A

Follicle centre cells

23
Q

Forms of follicle centre cells

A

Centrocytes - cleaved nuclei

Centroblasts - several nuclei

24
Q

Difference between a primary and secondary lymphoid follicle

A

Secondary has a pale staining central area called the germinal centre (site of B cell proliferation)

25
Q

What surrounds the germinal centre of a secondary follicle

A

Mantle zone containing B cells to be transformed into plasma/memory cells and a few T cells

26
Q

What do T cells do when an antigen is presented to them

A

Promote development of B cell type producing complementary antibody by releasing cytokines (IL4)
B cell -> Centrocyte -> Centroblast

27
Q

What happens to centroblasts after leaving the follicle

A

Move to the paracortex and medullary sinuses where they become immunoblasts

28
Q

What do immunoblasts give rise to

A

Plasma cells

Memory B cells

29
Q

What cells does the paracortex of a lymph node contain

A

Lymphocytes (mainly T)
Supporting cells
Accessory cells

30
Q

What’s the predominant cell type in the lymph node medulla

A

Macrophages

31
Q

What structures are in the lymph node medulla

A

Blood vessels
Medullary cords
Medullary sinuses

32
Q

What cell type is predominant in medullary cords and what is the consequence of this

A

Plasma cells

Antibodies produced by the plasma cells pass from the medullary cords to the efferent lymphatic vessel

33
Q

How do lymphocytes enter the lymph nodes (give percentages)

A

10% from lymph via afferent lymph vessels

90% from the blood via HEVs

34
Q

Describe the passage of lymph through a lymph node

How does this relate to immune response

A

Afferent lymphatics -> marginal sinus -> cortical sinus -> medullary sinus -> efferent lymphatics
Macrophages remove particulate matter in the lymph
Antigen presenting cells facilitate the immune response to antigens in lymph

35
Q

What is red pulp

A

Blood filtration system in the spleen

36
Q

What is white pulp

A

Part of the spleen with a similar structure to lymph nodes containing lots of T cells, B cells and accessory cells

37
Q

Function of red pulp

A

Removes old or damaged RBCs from the circulation

38
Q

Function of white pulp

A

Mounts an immune response to antigens within the blood

39
Q

Possible effects of a splenectomy

A

Enhanced susceptibility to infection, especially by streptococci pneumoniae, haemophillus influenza and meningococcus

40
Q

Where is GALT

A

Waldeyer’s ring - includes tonsils and adenoids
Peyer’s patches
Accumulates in appendix, large intestine, stomach (with age) and gut lamina propria

41
Q

What are peyer’s patches

A

Aggregates of lymphoid tissue found in the small intestine which generate an immune response within the mucosa

42
Q

Features of peyer’s patches

A 
M cells (epithelial cells with microfolds)
No HEVs
43
Q

Describe the immune response of peyer’s patches

A

B cells stimulated by antigen
Cells pass to mesenteric lymph nodes where the response is amplified
Activated lymphocytes pass into the circulation via the thoracic duct
Activated lymphocytes home into the gut to carry out final effector functions

44
Q

Consequence of lymphocytes (and some phagocytes) recirculating between lymphoid and non-lymphoid tissue

A

Helps lymphocytes (and some phagocytes) to be exposed to the antigens they recognise so they can be distributed to sites where they are needed

45
Q

Give examples of immune cells and their pattern of recirculation

A

Naive lymphocytes - from primary (where lymphocytes mature) to secondary (where lymphocytes interact to generate immune response) lymphoid tissue via blood
Activated lymphocytes - from spleen, MALT and lymph nodes to blood, to other lymphoid and non-lymphoid tissue
APCs (macrophages and dendritic cells) - carry antigen from the periphery to lymphoid tissue

46
Q

What does the pattern of recirculation depend on

A

State of activation
Adhesion molecules expressed by endothelial cells
Chemotactic molecules

Immunity and infection (1 decks)

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