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05 FdSc Bioscience - Human Physiology and Disease > Week 8 - the lymphatic system and immunity > Flashcards

Week 8 - the lymphatic system and immunity Flashcards

1
Q

What are the lymphatic and immune systems responsible for?

A
  • They are responsible for protecting us against foreign substances and infections
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2
Q

What are the three barriers of defence in the human body?

A
  1. To block invaders out, i.e. skin and mucous membranes
  2. Inducing inflammatory response
  3. Production of antibodies
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3
Q

What is the relationship between the immune system and the lymphatic system?

A
  • The immune system is closely associated with the lymphatic system
  • The two terms are often used interchangeably and refer to the bodies ability to defend against pathogens
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4
Q

What does the lympatic system consist of?

A
  • It consists of a network of vessels that penetrate nearly every tissue in the body, and a collection of tissues and organs that produce immune cells
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5
Q

What are the main functions of the immune/ lymphatic sytem system?

A
  1. Fluid recovery - absorbs excess fluid from tissue spaces and returns it to blood stream via lympatic vessels
  2. Immunity - fluid recovered by lymph vessels contains foreign cells and chemicals from tissues, it passes through the lymph nodes which contain immune cells which detect pathogens and activate a protective immune response
  3. Lipid absorption - lacteals are lymphatic vessels located in the small intestine which aborb dietary lipids that are not absorbed by capillaries
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6
Q

What is the lypmatic system composed of?

A
  • Lymph (recovery fluid)
  • Lympatic vessels (to transport the lymph)
  • Lymphatic tissue (lympocytes and macrophages)
  • Lymphatic organs (concentrated with immune cells)
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7
Q

What is lymph?

A
  • It originates as blood plasma that leaks from the capillaries to become interstitial fluid
  • Once in the lymphatic system the interstitial fluid is called lymph but has a similar composition to the original intersitial fluid
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8
Q

Describe the structure of lymphatic vessels

A
  • Similarly to veins, lypmpahtic vessels also contain valves
  • They have tunica interna and tunica media
  • Their walls are thinner and they have more valves than veins
  • There is a continual recycling of fluid from blood to lymph
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9
Q

Describe the course that lymph takes through the lymphatic system on the way back to the bloodstream

A
  1. Lymphatic capillaries
  2. Collecting vessels
  3. Lymphatic trunks
  4. Collecting ducts
  5. Subclavian veins
  • The lymphatic capillaries join together to form the collecting vessels
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10
Q

Where are collecting vessels typically found in relation to other structures?

A
  • Collecting vessels are typically found alongside veins and arteries
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11
Q

Where are lymph nodes located?

A
  • There are several lymph nodes in the lymphatic system, interspersed along the collecting vessels, which receive and filter the lymph
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12
Q

What do collecting vessels join together to form?

A
  • Collecting vessels join to form large lymphatic trunks with each draining a larger portion of the body
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13
Q

Give some examples of the main lymphatic trunks

A
  • The main lymphatic trunks include:
    • Lumbar trunk
    • Intestinal trunk
    • intercostal trunk
    • Bronchomediastinal trunk
    • Subclavian trunk
    • Jugular trunk
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14
Q

What do the lymphatic trunks join together to form?

A
  • Lymphatic trunks join together to form the two collecting ducts:
    1. Thoracic duct
    2. Right lymphatic duct
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15
Q

Describe the thoracic duct

A
  • This duct is larger than the right lymphatic duct and receives lymph from the abdomen, lower extremities and left side of the upper body
  • It begins as a sac in the abdominal cavity called the cisterna chyli which serves as a temporary holding area for lymph which then passes through the diaphragm
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16
Q

Describe the right lymphatic duct

A
  • Right lymphatic duct begins in the right thoracic cavity and receives lymph drainage from the right side of the upper body and thoracic area
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17
Q

How is the flow of lymph assisted?

A
  • Flow is lymph is assisted by rhythmic contractions of the lymphatic vessels
  • Similar to veins, lymphatic vessels are also assisted by skeletal muscles which squeeze them to force the movement of lymph
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18
Q

What are primary lymphatic organs?

A
  • The primary lymphatic organs are red bone marrow and the thymus - they are the sites of the production and maturation of lymphocytes (WBCs)
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19
Q

What is red bone marrow responsible for?

A
  • Red bone marrow is the site of blood cell production, some of the white blood cells produced in the marrow include:
    • Neutrophils
    • Basophils
    • Eosinophils
    • Monocytes
    • Lymphocytes
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20
Q

What are the types of lymphocyte and why are they named in this way?

A
  • There are B lymphocytes and T lymphocytes
    • Red bone marrow is the site of maturation for B lymphocytes and the thymus is the site of maturation for T lymphocytes
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21
Q

Describe the location and role of the thymus gland in the lymphatic system

A
  • Thymus gland is a small lymphoid organ situated in the mediastinum, which extends upwards into the midline of the neck
  • Most active in children
  • Gland is a member of both the lymphatic and endocrine systems
  • It produces thymic hormones such as thymosin, which aids in the maturation of T lymphocytes
  • Immature T lymphocytes travel from the bone marrow to the thymus via the blood stream
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22
Q

What are the secondary lymphatic organs?

A
  • Secondary lymphatic organs play an important role in the immune system and it includes:
    • Spleen
    • Lymph nodes
    • Tonsils
    • Appendix
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23
Q

Describe the spleen as a secondary lymphatic organ

A
  • It is the bodys largest lymphatic organ and is situated in the upper quadrant of the abdomen
  • Composed of two tissue types:
    1. Red pulp - consists of sinuses and erythrocytes
    2. White pulp - consists of lymphocytes and macrophages
  • Similar to lymph nodes, the spleen monitors the composition of pathogens in the blood
  • Lymphocytes and macrophages respond rapidly to foreign antigens in the blood and activate immune reactions
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24
Q

Describe the lymph nodes as secondary lymphatic organs

A
  • They are small structures located along the lymphatic vessels
  • They have two main functions:
    1. Cleanse the lymph
    2. Alert the immune system to pathogens
  • Lymph nodes are situated in each cavity of the body except the dorsal cavity
  • When body fights infection lymph nodes quickly multiply and swell
    • Physicians often detect the bodys reaction to infected by feeling for swollen or tender lymph nodes
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25
Q

Describe the tonsils as secondary lymphatic organs

A
  • They are patches of lypmatic tissue situated at the entrance to the pharynx where they guard against ingested and inhaled pathogens
  • There are three pairs of tonsils:
    1. Pharyngeal tonsil
    2. Palatine tonsil
    3. Lingual tonsil
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26
Q

Describe Peyer’s patches as secondary lymphatic organs

A
  • They are located in the wall of the intestine and the appendix and they are attached to the cecum of the large intestine
  • They intercept pathogens that enter the body through the intestinal tract
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27
Q

Define the term “immunity”

A
  • Immunity is the ability to resist damage from foreign substances
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28
Q

What are the different categories of immunity?

A
  • Immuity is categorised as either innate immunity or adaptive immunity
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29
Q

Briefly outline innate immunity

A
  • The body recognises and destroys specific foreign substances but the response to them is the same each time
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30
Q

Briefly outline adaptive immunity

A
  • The body recognises and destroys foreign substances but the response to them improves every time
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31
Q

What do the main componets of innate immunity include?

A
  1. Mechanical mechanisms that prevent the entry of microbes into the body
  2. Chemical mediators that act directly against the microorganism
  3. Cells involved in phagocytosis
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32
Q

What are examples of physical barriers in the innate immunity?

A
  • The skin and mucous membranes provide a barrier for microorganisms to enter the body and spread through tissues
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33
Q

Describe how the skin acts as an external barrier in the innate immune response

What is a concern if the skin is broken?

A
  • Sebaceous glands in the skin produce sweat and sebum which help protect the skin because they both contain antiseptic molecules that destroy the cell wall of bacteria
    • When the skin is broken one of the most urgent treatment concerns is the prevention of infection
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34
Q

Describe how mucous membranes act as an external barrier in innate immunity

A
  • Digestive, respiratory, urinary and reproductive tracts are all exposed to the external environment making them succeptible to invasion by pathogens
    • They are protected by mucous membranes
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35
Q

Give an example of mucous membranes acting as an external barrier in the innate immune response

A
  • In the respiratory tract ciliated mucous membranes sweep microbes trapped in the mucous to the back of the larynx where they are swallowed
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36
Q

Besides mucous membranes, what other mechanisms in the respiratory tract act as barriers in innate immunity?

A
  • Coughing and sneezing are additional mechanisms that remove microorganisms
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37
Q

What is the role of inflammation in innate immunity?

A
  • Inflammation is a local defensive response to tissue injury including trauma and infection
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38
Q

What are the main functions of inflammation in innate immunity?

A
  • The main functions of inflammation in the innate immune response include:
  1. To reduce the spread of pathogens
  2. To remove debris of damaged tissue
  3. To initiate tissue repair
39
Q

What are the signs of inflammation in the innate immune response?

A
  1. Swelling
  2. Redness
  3. Heat
  4. Pain
40
Q

What is the “complement system” in innate immunity?

A
  • It is a biochemical cascade of the immune system that helps remove pathogens and promotes healing
  • This system is referred to as a non-specific defence which is activated by antibody-antigen complexes
41
Q

What does the complement system require in order to work?

A
  • It requires the cooperation of several plasma proteins that work together to result in cytolysis by disrupting the target cell’s plasma membrane
42
Q

What are interferons in innate immunity?

A
  • Interferons are glycoproteins secreted by cells that have been invaded by viruses
43
Q

What is the function of interferons in innate immunity?

A
  • Their main function is to interfere with viral growth by diffusing into neighbouring cells and stimulating them to produce antiviral proteins which prevent the multiplication of viruses within them
44
Q

What are leukocytes and how are they divided in innate immunity?

A
  • They are the primary cells of the immune system and are divided into six types:
  1. Neutrophils
  2. Eosinophils
  3. Basophils
  4. Lymphocytes
  5. Monocytes
  6. Dendritic cells
45
Q

What is the term phagocyte used to describe in innate immunity?

A
  • Phagocytes are classified as a functional group of leukocytes who engulf and ingest their targets by phagocytosis
  • This group includes:
    1. Neutrophils
    2. Eosinophils
    3. Monocytes
    4. Macrophages
46
Q

What is the term cytotoxic cells used to mean in innate immunity?

A
  • Cytotoxic cells are a second functional group that destroys their target cells, this group includes:
    • Eosinophils
    • Specific types of lymphocytes
47
Q

What are neutrophils in innate immunity?

A
  • Motile cells
  • Destroy cells by phagocytosis and digestion
  • Similar to leukocytes in that they are synthesised in bone marrow
  • Release cytokines
48
Q

What are eosinophils in innate immunity?

A
  • They phagocytose:
    • antigen-antibody complexes
    • allergen
    • inflammatory chemicals
  • Attach to large parasites and release substances from their granules that destroy parasites
49
Q

What are basophils in innate immunity?

A
  • Secrete heparin and histamine which aid in the motility of other leukocytes
  • Release mediators that contribute to inflammation
50
Q

What are lymphocytes in innate immunity?

A
  • Key cells that mediate acquired immunity
  • Natural killer (NK) cells are a type of lymphocyte that atach and lyse host cells that have either become infected or have become cancerous
  • NK cell recognises abnormal cell it releases perforins which perforate the cell surface and destroys the cell
51
Q

What are dendritic cells in innate immunity?

A
  • They activate lymphocytes
  • Responsible for recongising and capturing antigens, they then migrate to secondary lymphoid tissues and present the antigens to lymphocytes
52
Q

What are monocytes in innate immunity?

A
  • They are precursors to macrophages
  • Once monocytes exit the blood they enlarge and differentiate into macrophages
53
Q

What is adaptive immunity?

A
  • This part of the immune system directly targets attacking microbes and the immune defenses respond to antigens
54
Q

What are antigens and epitopes?

A
  • An antigen is any molecule that triggers an immune response
  • Only specific regions of an antigen molecule, called epitopes, stimulate immune responses
  • Generally our immune system doesn’t respond to our own antigens and if it does it is called an autoimmune disease
55
Q

What is meant by the term allergenic response?

A
  • An immune response to harmless antigens such as pollen is known as an allergic response
56
Q

What does the immune system consist of?

A
  • It is not an organ, it consists of a group of distributed cells that recognise foreign substances and act to neutralise or destroy them
57
Q

What are the two characteristics that differentiate the adaptive response from the innate immune response?

A
  1. Specificity - the ability of the adaptive immune system to recognise a specific antigen
  2. Memory - the ability to remember previous encounters with a speicifc antigen and induce a more rapid response next time
  • In innate immunity, each time the body is exposed to an antigen the response is the same due to a lack of specificity and memory of previous encounters
58
Q

How are lymphocytes important in adaptive immunity?

A
  • Specific immunity is dependant upon B lymphocytes and T lymphocyte (B/T cells)
  • Both B and T cells recognise target antigen-bearing cells although they both use different mechanisms
59
Q

What is the role of B lymphocytes in adaptive immunity?

A
  • Mainly responsible for humoral immunity (antibody-mediated immunity)
  • Produce antibodies which are proteins that bind with and neutralise specific antigens
  • When antibodies bind to viruses they can prevent the virus from infecting cells
  • When antibodies bind to toxins they stimulate neutralisation
60
Q

What cells do B lymphocytes produce?

A
  • B lymphocytes produce plasma and memory cells
61
Q

Describe the production of plasma cells in the adaptive immune response

A
  • B cells have specific surface receptors allowing them to detect certain antigens
  • B cells are distributed through lymph nodes, spleen and tonsils
  1. B cells inactive until they enounter an antigen on a foreign cell
  2. Macrophages and T cells act as antigen presenting cells (APCs) and interact with B lymphocytes
  3. B cells bind to the antigen which activates the B cell
  4. B cells multiply into a large homogeneous group (clone)
  5. Majority of these clone cells are plasma cells which secrete antibodies to bind to the epitope
62
Q

What are memory cells?

A
  • Once B cells active, some of the clones become long-lived memory cells
  • Memory cells record information about the foreign antigen so antibodies can be made more quickly upon second exposure
63
Q

What are the different classes of antibody?

A
  • Antibodies aka immunoglobulins
  • Several different classes:
    • IgA
    • IgG
    • IgE
    • IgM
64
Q

What is the function of antibodies in the adaptive immune system?

A
  • Attach to surface of foreign antigen to make it more easily phagocytosed by neutrophils, monocytes and macrophages
  • Antibodies which bind and inactive toxins are known as antitoxins
  • Antibodies can bind to surface of microbes and prevent them from entering host cells
  • Antibodies can stimulate the complement system
65
Q

What are T lymphocytes responsible for?

A
  • T cells are responsible for defending the body against intracellular pathogens
    • Referred to as cell-mediated immunity
66
Q

What is the relationship between T cells and macrophages?

A
  • Macrophages are responsible for phagocytosing invading microbes and digesting it into molecular fragments
  • Macrophages display the epitopes of antigens to T cells
67
Q

What classes of cell does cell-mediated immunity involve?

A
  • It involves:
  1. Cytotoxic T cells
  2. Helper T cells
  3. Suppressor T cells
  4. Memory T cells
68
Q

What are cytotoxic T cells responsible for in cell-mediated immunity?

A
  • They migrate to the site of infection and carry out the attack on virally infected cells and tumor cells be secreting perforins to perforate the cells resulting in lysis
69
Q

What are T helper cells responsible for in cell-mediated immunity?

A
  • Promote the action of cytotoxic cells and play a role in humoral immunity (unlike other T cells which are only involved in cell-mediated immunity)
  • These cells are targeted in a HIV infection
70
Q

What are suppressor T cells responsible for in cell-mediated immunity?

A
  • They limit the cell-mediated attack and stimulate other T cells and B cells
71
Q

What are memory T cells responsible for in cell-mediated immunity?

A
  • They are antigen-specific T cells that persist long-term after an infection has resolved
  • They are descended from cytotoxic T cells
  • Responsible for memory in cell-mediated immunity
72
Q

Define the term acquired immunity

A
  • Acquired immunity responsed are antigen-specific responses in which the body recognises a foreign substance and reacts to it
73
Q

How can acquired immunity be divided?

A
  • Can be subdivided into active and passive acquired immunity
74
Q

When does active immunity occur?

Describe two situations in which it may occur

A
  • Occurs when body’s exposed to a pathogen and produces its own antibodies
  • Can occur naturally, when a pathogen invades the body, and artificially when given vaccinations containing disabled or killed microorganisms
75
Q

How do vaccinations occur in acquired active immunity?

A
  • In vaccinations the antigens have been modified so that they stimulate an immune response but won’t cause symptoms of disease
    • E.g. MMR vaccination against measels, mumps and rubella
76
Q

What is passive acquired immunity?

A
  • It is temporary immunity that results from acquiring antibodies produced by another individual
77
Q

Describe different examples of passive acquired immunity

A
  • Transfer of antibodies from mother to foetus across placenta
  • Baby acquired antibodies through milk after birth
  • Injection of immune serum obtained from another individual that produced antibodies - this is artificial passive immunity
78
Q

What is the difference between active and passive immunity?

A
  • Passive immunity generally lasts 2-3 weeks or until the acquired antibody is degraded
  • Active immunity occurs indefinitely
79
Q

Name one Immunodeficiency disease

A
  • Acquired Immunodeficiency disease (AIDS) is a life threatening disease
80
Q

What is AIDS and can be the result of this disease?

A
  • AIDS is a collection of symptoms and infections resulting from damage to the immune system caused the the human immunodeficiency virus (HIV)
  • The late stage of AIDS leaves individuals prone to infection and tumors
81
Q

How does HIV cause AIDS and what is the effect on the immune system?

A
  • HIV is a retrovirus that mainly infects components of the human immune system such as T helper cells (CH4+ T Cells), macrohpages and dendritic cells
  • HIV destroys CH4+ cells which are fundamental for correct functioning of the immune system, cell-mediated immunity is lost resulting in AIDS
82
Q

What are the strains of HIV involved in causing AIDS?

A
  • HIV-1 is responsible for the majority of cases of AIDS
  • HIV-2 is most prominent in West Africa
83
Q

How does a HIV infection progress?

A
  • It progresses over time from acute HIV infection to latent HIV infection then to early symptomatic HIV infection before finally to AIDS
84
Q

How is AIDS identified?

A
  • It is mainly identified by the amount of CH4+ T cells in the blood and the presence of certain infections
85
Q

How is HIV transmitted?

A
  • Transmitted through direct contact of a mucous membrane or the bloodstream from an infected person to a non-infected person
  • Transmission can occur through exchange of blood, vaginal fluid, semem and breast milk
86
Q

How is a HIV infection treated?

A
  • Currently there are no cures
  • Treatments exist to slow the progression of the virus
87
Q

Name three autoimmune diseases

A
  • Vitiligo
  • Multiple sclerosis
  • Juvenile-onset diabetes
88
Q

What is vitiligo ?

A
  • Autoimmune disorder in which the immune system targets and destroys melanocytes - pigment making cells
  • Causes irregular white patches on the surface of the skin which can affect different parts of the body
89
Q

What is multiple sclerosis?

A
  • Chronic degenerative disorder of the central nervous system
  • Immune system attacks and destroys myelin in the CNS
  • Causes multiple scars on the myelin sheath resulting in the loss of nerve function
90
Q

What is juvenile-onset diabetes?

A
  • Autoimmune disorder in which the beta cells of the pancreas are attacked thus insulin is not produced
91
Q

What is the immune response to allergies known as?

What are the two types of this?

A
  • Referred to as hypersensitivity or sensitivity to the antigen
  • Immediate hypersensitivity and delayed hypersensitivity
92
Q

What is immediate hypersensitivity?

A
  • Immune response to an allergy
  • Immediate hypersensitivity is induced by antibodies and occurs within minutes of exposure to the allergen (antigen)
93
Q

What is delayed hypersensitivity? Regarding the immune system

A
  • Delayed hypersensitivity reactions are induced by helper T cells and macrophages
  • May take several days to develop
94
Q

What is type 1 hypersensitivity, how is it mediated and what are the symptoms?

A
  • Type 1 hypersensitivity is an allergic reaction caused by re-exposure to a specific allergen
  • Mediated by IgE antibodies and the release of histamines
  • Can be local or systemic and symptoms can range from mild irritation to sudden death from anaphylactic shock

05 FdSc Bioscience - Human Physiology and Disease (8 decks)

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