Cilia and the Protection of the Respiratory Tract
Introduction
Approximately twelve thousand litres of air is inhaled by one person each day containing environmental stimuli including pathogens and particles such as toxic pollutants and allergens. These must be expelled from the body as it may induce airway inflammation and infection, causing airway diseases. Mucociliary clearance acts as an innate defence against these stimuli, where cilia is a part of this mechanism. Cilia, microscopic organelle extensions, beat orderly to propel mucus with embedded substances out of the respiratory system. When this mechanism becomes disrupted, pulmonary infections occur and chronic airway diseases may arise to be severe, emphasising the importance of cilia. …show more content…
Each doublet contains two rows of dynein (outer and inner) radical spokes which link inner microtubules with the outer ones and nexin links linking outer microtubules to one another (refer to figure 2) (6,7). The outer dynein arms and nexin have an important role in cilia motility.
Cilia Motility
The function of cilia is relied on its motility consisting of sliding microtubules causing bending movement, resulting in mucus propulsion and aiding mucociliary clearance. Bitter receptors are also present, acting as sensory component to detect toxic substances.
The movement of dynein arms along adjacent outer doublet microtubules while pulling adjacent filaments, causes ciliary bending (6, 8, 9)
For the sliding motion to be activated, energy is required. Energy is provided through hydrolysis of adenosine triphosphate (ATP) by the dynein ATPase. (10).
Activation of dynein arms causes the sliding motion of a microtubules doublet on an adjacent doublet (refer to figure 4) (2). Restriction of sliding by nexin links keep doublets intact and through radical spoke heads, it is converted into a bending motion during the ciliary stroke (refer to figure 5 and 6) …show more content…
During the effective stroke, the cilium is fully extended where the distal tip makes contact with the viscous mucus layer (refer to figure 8) (2,11,12). This minimises a restraining effect that exerts a high influence on the fluid (11). As this moves at a high velocity, the mucus layer containing hazardous particles is transported out of the airways as the directional forces is transmitted (2,11). As the speed of the effective force is increased, this leads to increased fluid propulsion, enhancing mucociliary clearance (11). This can be caused by a rise in dynein-microtubule interactions and is provided when necessary
Introduction
Approximately twelve thousand litres of air is inhaled by one person each day containing environmental stimuli including pathogens and particles such as toxic pollutants and allergens. These must be expelled from the body as it may induce airway inflammation and infection, causing airway diseases. Mucociliary clearance acts as an innate defence against these stimuli, where cilia is a part of this mechanism. Cilia, microscopic organelle extensions, beat orderly to propel mucus with embedded substances out of the respiratory system. When this mechanism becomes disrupted, pulmonary infections occur and chronic airway diseases may arise to be severe, emphasising the importance of cilia. …show more content…
Each doublet contains two rows of dynein (outer and inner) radical spokes which link inner microtubules with the outer ones and nexin links linking outer microtubules to one another (refer to figure 2) (6,7). The outer dynein arms and nexin have an important role in cilia motility.
Cilia Motility
The function of cilia is relied on its motility consisting of sliding microtubules causing bending movement, resulting in mucus propulsion and aiding mucociliary clearance. Bitter receptors are also present, acting as sensory component to detect toxic substances.
The movement of dynein arms along adjacent outer doublet microtubules while pulling adjacent filaments, causes ciliary bending (6, 8, 9)
For the sliding motion to be activated, energy is required. Energy is provided through hydrolysis of adenosine triphosphate (ATP) by the dynein ATPase. (10).
Activation of dynein arms causes the sliding motion of a microtubules doublet on an adjacent doublet (refer to figure 4) (2). Restriction of sliding by nexin links keep doublets intact and through radical spoke heads, it is converted into a bending motion during the ciliary stroke (refer to figure 5 and 6) …show more content…
During the effective stroke, the cilium is fully extended where the distal tip makes contact with the viscous mucus layer (refer to figure 8) (2,11,12). This minimises a restraining effect that exerts a high influence on the fluid (11). As this moves at a high velocity, the mucus layer containing hazardous particles is transported out of the airways as the directional forces is transmitted (2,11). As the speed of the effective force is increased, this leads to increased fluid propulsion, enhancing mucociliary clearance (11). This can be caused by a rise in dynein-microtubule interactions and is provided when necessary