Lymphatic System Flashcards

1
Q

What is the difference between an antibody and an antigen?

A

Antibody is a protein molecule released by a plasma cell & binds to a specific antigen

Antigen is a surface marker that the body perceives as foreign

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2
Q

What are the vessels in the lymphatic system called, where do they start and where do they end?

A

Vessels = lymphatics
Start: peripheral tissues
End: venous system

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3
Q

What is the fluid called in the lymphatic system ?

A

Lymph

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4
Q

What do the organs of the lymphatic system contain?

A

Many lymphocytes

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5
Q

What are the functions of the lymphatic system?

A
  • produce, maintain and distribute lymphocytes
  • maintain NFP (net filtration pressure) by returning fluid and solutes from interstitial fluid to blood
  • distribute hormones, nutrients and waste
  • removes foreign substances and aged/infected/cancerous cells
  • provides structural basis of immune system
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6
Q

What is the lymph pathway?

A

Blood stream capillaries –> interstitial space –> Lymphatic capillaries –> lymphatic vessels –> Lymphatic trunks –> lymphatic ducts –> Venous blood

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7
Q

What are the differences between lymphatic capillaries and blood capillaries?

A

Lymph capillaries are:

  • blind ended
  • very permeable
  • made of endothelial cells overlapping to make one way minivalves
  • anchored by collagen filaments preventing capillary collapse
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8
Q

What is a lacteal?

A

Specialized lymph capillaries in the small intestinal mucosa –> absorb digested fat and bring chyle to the blood stream

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9
Q

What is chyle?

A

fatty lymph

*not brought to the liver (metabolized too quickly)

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10
Q

Where are lymphatic capillaries not found?

A

Bones, bone marrow, teeth and CNS

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11
Q

What are some of the properties of lymphatic vessels?

A
  • lined by simple squamous epithelium
  • surrounded by thin layer of connective tissue and small amounts of smooth muscle
  • contain internal valves to ensure unidirectional flow
  • anastomose often
  • travel with blood vessels
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12
Q

What does anastomose mean?

A

mesh or plexus of vessels coming together –> 2 becoming 1

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13
Q

What do the lymphatic trunks do?

A

Drain different body regions

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14
Q

What areas do the right lymphatic duct and thoracic duct drain?

A

Right lymphatic duct drains right body superior to diaphragm

Thoracic duct drains everything else (right below diaphragm and entire left side)

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15
Q

How does lymph move through the body?

A

Very slowly –> not propelled by a pump and is a low pressure system
Lymph is propelled by the same things that promote venous return:
- respiratory pump
- valves
- skeletal muscle “milking”

AND

  • pulsations of nearby arteries
  • contractions of smooth muscle in walls of lymphatics
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16
Q

How does breathing help move lymph?

A

Changes pressures in the thorax and abdomen; negative pressures and volumes in the thorax help pull fluid

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17
Q

What are the classes of lymphocytes?

A

T cells (80%)

B cells (10-15%)

NK cells (5-10%)

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18
Q

What are the subtypes of T cells?

A
  1. Cytotoxic T cells –> attack foreign cells or infected body cells
  2. Helper T cells –> stimulate activation of T and B cells
  3. Suppressor T cells –> inhibit activation of T and B cells which helps establish and control the sensitivity of the immune response
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19
Q

What does a plasma cell do?

A

B Cells differentiated = Plasma cells

Produce and secrete antibodies responsible for antibody-mediated immunity (humoral)

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20
Q

What does an NK cell do?

A

NK = Natural killer

immune surveillance, attack foreign bodies, cells that are infected and cancer cells

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21
Q

How do NK cells work?

A
  1. unusual antigen (Ag) recognized by NK and becomes activated; NK adheres to target cell
  2. NK golgi moves so the face points at abnormal cell; Golgi produces secretory vesicles containing perforins
  3. Perforins are released at NK cell surface and diffuse across narrow gap separating NK cells from target
  4. Perforins create pores that make the abnormal cell unable to maintain the boundary between internal and external environments
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22
Q

What are the other lymphoid cells and their functions?

A

Macrophages: phagocytize foreign substances and help activate the T cells

Dendritic cells: capture antigens and deliver them to lymph nodes

Reticular cells: make stroma/framework so the organs don’t collapse

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23
Q

What is the difference between primary and secondary lymphoid organs?

A

Primary is where the B & T cells mature (bone marrow and thymus)

Secondary is where B & T cells encounter antigens (tonsils, lymph nodes, spleen, peyer’s patch and appendix)

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24
Q

Where do the T cells get their “education” and through which processes does this happen?

A

Thymus

Positive selection: T cells must first be able to recognize self MHC, if they cannot, they undergo apoptosis

Negative selection: T cells must fail to bind to the self-Ag because that would mean potential for an autoimmune disorder, cells that recognize self-Ag cells undergo apoptosis

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25
Q

What is the function of lymphoid tissue?

A
  • provides site of lymphocyte proliferation

- surveillance point; makes sure everything belongs to the self and is healthy

26
Q

What are the different types of lymphoid tissue?

A

Diffuse lymphatic tissue: lymphoid cells and some reticular fibers found in almost every body organ

Lymphoid follicles: solid, spherical bodies of tightly packed lymphoid cells and reticular elements
–> germinal center is mostly proliferating B cells

27
Q

What are the functions of a lymph node?

A
  • filter lymph: macrophages destroy microorganisms and debris
  • activate the immune system: activated and mount attack against antigen
  • recall that all lymphoid organs contain lymphocytes and would be able to start an immune response
28
Q

What are trabeculae?

A

inward extensions of the capsule surrounding a lymph node

29
Q

Where are the follicles with germinal centers found in the lymph node?

A

Cortex

30
Q

What two structures are contained in the medulla of the lymph node?

A

Medullary cords: inward extensions from the cortex

Medullary sinuses: large lymph capillaries containing macrophages

31
Q

Are there more afferent or efferent lymphatic vessels in lymph nodes? Why?

A

There are more afferent vessels (ones coming into the node) because this allows for everything coming in to be thoroughly filtered and there is more time to start an immune response if necessary

32
Q

What are some of the features of the spleen?

A
  • largest lymphoid organ
  • left side of the body between stomach and kidneys
  • in fibrous capsule and trabeculae
  • contains lymphocytes, macrophages and lots of red blood cells
33
Q

What types of pulp are found in the spleen and what are the functions?

A

White pulp: mostly lymphocytes and reticular fibers; allows for B & T cells to interact with substances in the blood, mount an immune response if necessary

Red pulp: rich in macrophages for disposal/recycling of worn out RBCs & bloodborne pathogens

34
Q

What are the functions of the spleen?

A
  • lymphocyte proliferation, immune surveillance and response
  • cleanses blood (gets rid of aged blood cells and debris)
  • stores products from breakdown of RBCs
  • stores blood platelets and monocytes for when needed
  • site offetal RBC production
35
Q

Can you live without a spleen?

A

Yes –> you have so much lymphatic tissue in your body that it isn’t necessary

36
Q

What does the stroma of the thymus consist of?

A

Star shaped epithelial cells

37
Q

What is MALT?

A

Mucosa-associated lymphatic tissue –> protects the digestive and respiratory systems from foreign matter
*tonsils, peyers patches, appendix

38
Q

What is the first line of defence against pathogens?

A

External barriers: skin and mucus membranes

39
Q

What is an acidic mantle?

A

there is an acidic mantle on the skin because secretions from the skin are acidic –> pH ~5.5
*this kills bacteria

There is also an acidic mantle in the vagina

And urine is acidic

40
Q

What is the second line of defence against pathogens?

A

These are the internal defences: Phagocytes, NK cells, antimicrobial proteins, inflammation, and fever

41
Q

What are antimicrobial proteins?

A

Interferons α, beta and gamma

  • -> proteins released by virus infected cells and certain lymphocytes
  • act as chemical messengers to protect uninfected tissue cells from viral takeover
  • mobilize the immune system
  • think of the cell that makes them as self-sacrificing
42
Q

What is a complement in terms of antimicrobial proteins?

A

complement is a group of blood borne proteins that lyse microorganisms, enhance phagocytosis by opsonization and intensify inflammatory and other immune responses
*non-specific, MAC (membrane attack complex) works the same as NK cells

43
Q

How is inflammation a defence against pathogens?

A

Results in heat and blood rushing to the area to flush everything out, the pain will stop us from using the area and prevents more damage

44
Q

How does fever protect against pathogens?

A

higher body temperature stops microbes from multiplying and enhances the body repair process

45
Q

What is humoral immunity and what is does it involve?

A

Humoral immunity is an adaptive immune defence –> B cells make antibodies to compliment antigens it encounters

Steps:
P - precipitation: soluble antigens get antibodies attaching onto them so its easier for the phagocytes to find them and destroy them

L - lysis: destruction of cells from complementation of antigen

A - agglutination: collects cells together to make them easier to find and phagocytose

N - neutralization: masking of dangerous parts of bacterial endotoxins

46
Q

What is the difference between primary and secondary responses to an antigen?

A

Primary responses: B cells are primed for specific antigens and when they are encountered, proliferation happens –> cells differentiate to plasma cells to secrete the antibody, memory B cell remains primed to respond to the same antigen

Secondary response: potentially years later, encountering the same antigen will cause proliferation very quickly

47
Q

What types of active humoral immunity are there?

A

Naturally acquired: contact with pathogen will get B cell memory - could potentially be very dangerous

Artificially acquired: vaccine with dead pathogens to introduce the antigen into the body

48
Q

What types of passive humoral immunity are there?

A

Naturally acquired: antibodies passed from mother to fetus via placenta or milk

Artificially acquired: injection of exogenous antibodies to fight the pathogen

49
Q

What is the major difference between active and passive humoral immunity?

A

MEMORY –> passive humoral immunity does not make memory B cells

50
Q

What is IgM and what does it do?

A

IgM (immunoglobulin M) is a pentamer antibody released in a PRIMARY humoral response

  • fixes and activates complement
  • good agglutinating agent (lots of binding sites on a pentamer)
51
Q

What is IgA, where is it found and what does it do?

A

IgA (immunoglobulin A) is a dimer antibody found in secretions (saliva, sweat, intestinal juice and milk)
- helps stop pathogens from attaching to epithelial cells

52
Q

What is IgD, where is it found and what does it do?

A

Monomer immunoglobulin found on B cell surface

- acts as an antigen receptor

53
Q

What is IgG, where is it found and what does it do?

A

IgG is a monomer immunoglobulin found most abundantly in plasma

  • main antibody for secondary and late primary responses
  • readily fixes and activates compliment
  • crosses placenta and confers passive immunity
54
Q

What is IgE and what does it do?

A

Immunoglobulin E monomer

  • binds to mast cells or basophils
  • antigen binding to receptor end triggers ells to release histamine and other chemicals mediating inflammation and allergic responses
55
Q

What is the second adaptive defence and how does it work? (3rd line)

A

Cellular immunity:
1. Cytotoxic T cells identify foreign antigen on MHC1 proteins and bind tightly to target cell

  1. Cytotoxic T cell releases perforin and granzyme molecules from its granules
  2. They insert into target cell membrane and make pores
  3. Granzymes enter through pores and trigger apoptosis in target cell
  4. Cytotoxic T cell detaches and finds more prey
56
Q

What types of cells display class 1 MHC proteins and what types of foreign antigens are there on the MHC?

A

All nucleated cells have class 1 MHCs and they will present endogenous antigens (intracellular pathogens or proteins made by cancerous cells)

57
Q

What types of cells have class 2 MHCs and what types of foreign antigens are presented on them?

A

APCs (antigen presenting cells) have class 2 MHCs and they present exogenous pathogens

58
Q

What is the difference between APCs and non-APCs when they send messages to the immune system?

A

APCs say: i belong to self but have captured and invader, this is what it looks like and kill anything that looks like it

Non-APCs say: I belong to self but have been invaded or become cancerous, kill me and stuff that looks like me

59
Q

What is CD8?

A

cytotoxic T cell –> really good at killing stuff

60
Q

In the third line of defence, what is the main difference between the B cells and T cells?

A

B cells make antibodies, T cells help make more antibodies and destroy all the B cells