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Respiratory Physiology > Lung Defence > Flashcards

Lung Defence Flashcards

1
Q

What is respiratory epithelium?

A

Ciliated, pseudostratified columnar epithelium

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2
Q

What are the functions of respiratory epithelium?

A
  • moistens airways
  • functions as a barrier to pathogens and foreign particles
  • prevents infection by action of mucociliary escalator. Particles adhere to mucus and are swept away by ciliary action to the pharynx to be swallowed.
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3
Q

Name the lung’s physical defence mechanism.

A

Coughing

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4
Q

How does coughing defend the lung?

A

Clears the bronchioles of secretions and foreign material.

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5
Q

How is a cough initiated?

A
  1. Receptors in larynx, trachea or bronchi are stimulated
  2. Impulse is sent to medullary inspiratory neurones which cause a deep inspiration
  3. The epiglottis closes and the vocal chords shut to entrap air in the lung
  4. Abdominal muscles contract, pushing the diaphragm
  5. Internal intercostal muscles contract forcefully
  6. Pressure in lungs rises, causing narrowing of trachea
  7. The large pressure difference between the airways and atmosphere causes a rapid flow rate of air expelled out of the trachea
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6
Q

Name a substance that inhibits the cough reflex.

A

Alcohol. Alcoholics are susceptible to choking and pneumonia.

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7
Q

Which property of epithelium allows it to regenerate after injury?

A

Functional plasticity

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8
Q

What is the consequence if epithelia cannot repair themselves and are defected?

A

Pulmonary disease

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9
Q

Is pulmonary disease caused by genetic or environmental factors?

A

Environmental

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10
Q

Name the types of asthma.

A
  1. Extrinsic - response to inhaled antigen
  2. Intrinsic - non-immune mechanism i.e. cold or exercise
  3. Bronchial - hyperactive airways lead to episodes of bronchoconstriction. Bronchoconstriction also results in excessive mucus production, leading to the formation of mucus plugs that obstruct airways
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11
Q

Name two types of immune system cell that are phagocytes.

A

Neutrophils

Macrophages

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12
Q

Name a type of immune system cell that makes antibodies.

A

Lymphocytes

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13
Q

Name the local response to infection in an innate immunity response.

A

Inflammation

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14
Q

What are the main functions of inflammation?

A
  • Destroy foreign invaders

- Set the stage for tissue repair

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15
Q

Which cells in the lung initiate inflammation?

A

Alveolar macrophages

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16
Q

How do cells recognise new pathogens?

A

By using pattern recognition receptors (PRRs), part of innate immunity

17
Q

Name a major receptor of macrophages which recognise common antigens on bacteria.

A

Toll-like receptor

18
Q

Which cells do alveolar macrophages arise from?

A

Monocytes

19
Q

Give the functions of alveolar macrophages.

A
  • phagocytosis
  • secrete toxic chemicals
  • present antigens to T helper cells
  • secrete cytokines for inflammation
  • clears apoptotic cells
20
Q

What is contained with neutrophils to help combat infection?

A

Primary and secondary granules

21
Q

What is contained within primary granules?

A

Elastase - breaks down elastin in lungs. This enables the neutrophil to migrate through the lung.

22
Q

What is contained within secondary granules?

A

Lysozyme - breaks down bacterial cell walls

Collagenase - breaks down collagen, allows neutrophil to penetrate collagen areas

23
Q

Describe the steps of neutrophil function.

A
  1. Identify the threat
    - uses receptors to detect mediators
    - recognises host opsonins
  2. Activation
    - via stimulus response G protein coupling
  3. Adhesion
    - neutrophil is tethered to endothelial cells of blood vessels to expose themselves to chemoattractants.
    - this induces production of integrins, another adhesion molecule. allows neutrophils to collect at site of injury rather than being washed away with blood
  4. Chemotaxis
    - neutrophils migrate into inflamed areas via diapedesis
    - neutrophils follow a chemotactic gradient
  5. Phagocytosis
    - opsonins bind to phagocytes to make it easier for neutrophils to target pathogens
    - pathogen is trapped in a phagosome within the neutrophil
  6. Bacterial killing
    - lysosomes destroy bacteria
24
Q

What is apoptosis?

A

Controlled cell killing. Cell is packaged and phagocytosed by neutrophils. No surrounding tissue damage.

25
Q

What is necrosis?

A

Reactive oxygen species kill cells and damage surrounding tissue. Cell suicide.

26
Q

Name the 2 layers of mucus.

A

Superficial mucous layer

Surfactant layer

27
Q

Name the two classes of cell of the adaptive immune system.

A

T-cells

B-cells

28
Q

Where are T-cells made?

A

Bone marrow, mature in thymus

29
Q

Name two types of T-cell and describe their functions.

A
  1. Cytotoxic T cell (killer cell)
    - bind to antigens on pathogen
    - directly kill the pathogen via chemicals
  2. T helper cell
    - assist in activation of B cells, macrophages + cytotoxic T cells via the expression of class II major histocompatibility complex (MHC) proteins on these cells
30
Q

Where are B cells made?

A

Bone marrow, mature in lymph nodes

31
Q

What is the function of B cells?

A

Antibody production.

32
Q

Name the 5 types of antibody.

A

IgA, IgD, IgE, IgG, IgM

33
Q

Describe the functions of macrophages.

A
  1. Recognition of non-self antigens in the presence of self antigens
  2. Development of immunological memory
34
Q

Why are antigen-presenting cells vital?

A

T cells can only bind to antigens when they are complexed with MHC proteins. Cells bearing MHC proteins are antigen-presenting cells.

35
Q

Which antibody is made to substances we are allergic to?

A

IgE

36
Q

What is the meaning of hypersensitivity in relation to immunity?

A

Refers to diseases in which immune responses to the antigens cause inflammation and damage to the body itself.

37
Q

Name the four types of hypersensitivity according to Gell & Coombs classification.

A

Type 1: IgE, allergic, acute. e.g. hay fever

Type 2: IgG, IgM bind to host cell antigens. Transfusion reactions and autoimmune disease

Type 3: IgG binds to antigen. Immune complexes e.g. Farmer’s lung (inhale mouldy hay)

Type 4: T helper and macrophage mediated delayed type hypersensitivity. Lots of cytokine secretion. E.g. TB

38
Q

Describe how type 1 reactions cause anaphylaxis (severe allergic reaction).

A
  1. Type 1 reactions cause the production of IgE
  2. T-helper cells trigger mast cells to secrete histamine and chemokines
  3. A local inflammatory response is created
  4. If the mast cells secrete a lot of histamine, anaphylaxis will occur = severe hypotension, vasodilation and bronchoconstriction
39
Q

What effect on immune function does an ageing lung have?

A

Decreased immune system function:

  • glandular epithelia decreases, so less protective mucus
  • less effective mucociliary system

Respiratory Physiology (11 decks)

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