Drive - defense (barrier and immunity) Flashcards
What is the purpose of respiratory epithelium?
To moisten and protect the airways.
Acts as a barrier to potential pathogens
Prevents infection by action of the mucociliary escalator
What type of epithelium (specifically) is respiratory epithelium?
Ciliated pseudostratified columnar epithelium
How do skin glands, salivary glands and lacrimal glands form part of the surface defence mechanism?
By secreting antimicrobial chemicals (e.g. antibodies, lysozymes, lactoferrin, mucus)
What is meant by the escalator mechanism?
Where particulates (and pathogens) that are stuck to the respiratory epithelium are swept by ciliary action up into the pharynx where they are then swallowed.
Physical barriers utilised by the lungs:
Coughing
Mucus
Describe the mechanism of coughing:
Deep inhalation
Epiglottis close and vocal cords shut tightly (air is trapped in lungs)
Abdominal muscle contract forcefully pushing the diaphragm upwards
Pressure in the lungs rises to 100mmHg or more
Increased intrathoracic pressure causes narrowing of the trachea
Vocal chords and epiglottis suddenly open wide
Large pressure differential (and trachea narrowing) produces rapid flow rate through the trachea
Air is expelled
What sort of velocities are reached (by the air) when coughing?
75 to 100 mph
Why are alcoholics more susceptible to choking and pneumonia?
As alcohol inhibits the cough reflex
What is the respiratory mucus secreted from?
The goblet cells of the airway surface epithelium and the submucosal glands
What does airways mucus consist of?
A viscoelastic gel containing water, carbohydrate, proteins and lipids.
What occurs after an epithelial injury (when the epithelium is damaged)?
Epithelium regenerates itself to form a full repair. Due to a level of function plasticity.
What causes pulmonary diseases?
Most are characterised by epithelia and thus sufferers have impaired host defence.
What causes the formation of mucus plugs and what do/can these cause?
As a result of excessive mucus production (due to bronchoconstriction. They can completely obstruct airways and are often fatal
What type of specialist tissue resident macrophage is found in the lungs?
Alveolar macrophages
What are the precursor cells to macrophages and where are they produced?
Monocytes - produced in the bone marrow.
What are the functions of the alveolar macrophages?
Resident phagocyte of the lungs
Co-ordinates the inflammatory response
Induction and clearance of apoptotic cells.
Destroy bacteria in the alveoli swiftly without inducing a massive immune response
If the macrophages cannot get rid of the pathogen what happens next?
Illicit a huge immune response - calling in neutrophils. This results in pneumonia.
What do primary granules contain?
Myeloperoxidase, elastase, cathepsins and defensins.
What do secondary granules contain?
Receptors, lysosome, collagenase.
Describe the mechanism of action by neutrophils: (5)
Identify the threat - through receptors
Activation
Adhesion
Migration/chemotaxis
Phagocytosis + bacterial killing
What occurs in necrosis?
Cells swell, lyse and reactive oxygen species and other enzymes are released.
Can cause damage to the surrounding tissue
Results in inflammation and phagocytosis of necrosed cell
What occurs in apoptosis?
(More controlled than necrosis)
Cell is turned off and packaged
Phagocytosed by neutrophils
No damage to the surrounding tissue
What type of antibody are made in an allergic reaction?
IgE
Name 2 possible causes of a type 1 IgE reaction
Acute anaphylaxis and hayfever
What type of immune reaction do pigeon fanciers lung sufferers have?
Type 3 - IgG
