Lung Defence Flashcards
What is respiratory epithelium?
Ciliated, pseudostratified columnar epithelium
What are the functions of respiratory epithelium?
- 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.
Name the lung’s physical defence mechanism.
Coughing
How does coughing defend the lung?
Clears the bronchioles of secretions and foreign material.
How is a cough initiated?
- Receptors in larynx, trachea or bronchi are stimulated
- Impulse is sent to medullary inspiratory neurones which cause a deep inspiration
- The epiglottis closes and the vocal chords shut to entrap air in the lung
- Abdominal muscles contract, pushing the diaphragm
- Internal intercostal muscles contract forcefully
- Pressure in lungs rises, causing narrowing of trachea
- The large pressure difference between the airways and atmosphere causes a rapid flow rate of air expelled out of the trachea
Name a substance that inhibits the cough reflex.
Alcohol. Alcoholics are susceptible to choking and pneumonia.
Which property of epithelium allows it to regenerate after injury?
Functional plasticity
What is the consequence if epithelia cannot repair themselves and are defected?
Pulmonary disease
Is pulmonary disease caused by genetic or environmental factors?
Environmental
Name the types of asthma.
- Extrinsic - response to inhaled antigen
- Intrinsic - non-immune mechanism i.e. cold or exercise
- 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
Name two types of immune system cell that are phagocytes.
Neutrophils
Macrophages
Name a type of immune system cell that makes antibodies.
Lymphocytes
Name the local response to infection in an innate immunity response.
Inflammation
What are the main functions of inflammation?
- Destroy foreign invaders
- Set the stage for tissue repair
Which cells in the lung initiate inflammation?
Alveolar macrophages
How do cells recognise new pathogens?
By using pattern recognition receptors (PRRs), part of innate immunity
Name a major receptor of macrophages which recognise common antigens on bacteria.
Toll-like receptor
Which cells do alveolar macrophages arise from?
Monocytes
Give the functions of alveolar macrophages.
- phagocytosis
- secrete toxic chemicals
- present antigens to T helper cells
- secrete cytokines for inflammation
- clears apoptotic cells
What is contained with neutrophils to help combat infection?
Primary and secondary granules
What is contained within primary granules?
Elastase - breaks down elastin in lungs. This enables the neutrophil to migrate through the lung.
What is contained within secondary granules?
Lysozyme - breaks down bacterial cell walls
Collagenase - breaks down collagen, allows neutrophil to penetrate collagen areas
Describe the steps of neutrophil function.
- Identify the threat
- uses receptors to detect mediators
- recognises host opsonins - Activation
- via stimulus response G protein coupling - 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 - Chemotaxis
- neutrophils migrate into inflamed areas via diapedesis
- neutrophils follow a chemotactic gradient - Phagocytosis
- opsonins bind to phagocytes to make it easier for neutrophils to target pathogens
- pathogen is trapped in a phagosome within the neutrophil - Bacterial killing
- lysosomes destroy bacteria
What is apoptosis?
Controlled cell killing. Cell is packaged and phagocytosed by neutrophils. No surrounding tissue damage.
