CTB6 - Cell Biology of the Respiratory Tract Flashcards
What are the two main functions of the airways?
Maximise airflow. Minimise airway damage.
Give four key features of the airway epithelium. Describe each briefly.
Goblet cells - chalice shaped cells protruding from epithelium into lumen. Secrete mucus.
Granules within the goblet cells - contain dehydrated glycosylated mucin proteins which undergo hydration and are released into lumen.
Ciliates cells - contain cilia to participate in mucociliary clearance, clearing the lumen when needed. Protective feature.
High mitochondrial density - provides metabolic energy for beating of cilia to allow for mucociliary clearance.
What is the main nutrient required from inspired air?
Oxygen
What types of exogenous particles may cause damage to the airway if allow to penetrate deep into the airways?
Pollen. Pollutants. Microbes. Tobacco. Noxious gases.
What is the main role of goblet cells, and which other airway epithelium structure do they work with, in order to perform this role?
Secretion of mucus - in the form of mucin glycoproteins. Work alongside submucosal glands.
Discuss the process of how mucus is secreted onto the airway lumen.
Dehydrated mucin granules present within goblet cells. They translocated within the cell to the apical surface. Open pore is formed upon fusion of granule with membrane. Water is absorbed by the granules via the pore. Granule swells to great extent, hydrated mucin are then released via exocytosis into airway lumen.
What is the role of ATP in mucin secretion?
ATP acts as a secretagogue - induces secretion of mucin.
Does the secretion of mucin from goblet cells occur only in vivo or in vitro?
Can occur in vitro provided that water is present. But does not need other cells to allow for mucin release.
Discuss the location of submucosal glands within the airways.
Found more abundantly in larger/proximal airways but not found in smaller distal airways,
Discuss why submucosal glands are so called.
Referred to as submucosal glands as a large proportion of the gland exists within the submucosal layer of the airway wall.
What are the two types of acini? How do they work together? Discuss how their location contributes to their function.
Serous acini - watery fluid secretion containing antibacterial lysozymes and lactoferrin.
Mucous acini - mucous secretion.
Serous acini are distal to mucous acini - allows watery fluid secretion from serous acini to wash the secretions of the mucous acini into the airway lumen,
What components are present within mucus?
High molecular weight proteins - mucins.
Water,
Electrolytes - sodium ions, chloride ions.
Proteins - lactoferrin, lysozymes
Describe the main purpose of the mucus and how it’s structure helps this.
Main role is to trap particles to avoid the, penetrating deep into the airways. Mucous is a viscoelastic gel like substance so is able to trap the particles
Are cilia located on the apical or basal surface?
Apical surface. Apical means towards the lumen. This is where cilia need to be to remove any particles within; the lumen.
How often do cilia beat?
Approx 9-17 beats per second.
What are cilia? Describe their structure.
Cell membrane extensions that fold to fold protrusions. Axoneme present within each protrusion which forms the core of the cilia. Anchored to cell via intracellular anchoring proteins. Microtubule structures connected by nexin and dynein.
What is dynein? What is its role in mucociliary clearance?
Dynein is a motor protein that is involved in the structure of the cilia. Ensure that cilia move in a synchronised manner, vital for mucociliary clearance.
What is the type of rhythm that mucociliary clearance has?
Metachronal rhythm
What are the two types of strokes performed by the cilia to allow for mucociliary clearance ? Briefly describe each.
Power/effective stroke - moves content within lumen forward and out of the lumen.
Recovery stroke - moves the cilia back to their original position to be loaded with the next region of mucus to be moved out of the lumen
Discuss the movement of the ciliated cells during mucociliary clearance.
Do not move. It is only the cilia of the ciliated cells that move.
Discuss the presence of airway smooth muscle at different stages of the airways.
All parts of the airway contain some smooth muscle. Greater amount of smooth muscle in the larger airways. Amount of smooth muscle decreases as you get into the smaller airways
Why is it important that all regions of the airway have smooth muscle?
Ensures that tone can be regulated readily - if substance was to enter the airways and penetrate further into the airways, contraction of smooth muscle can close that airway and prevent the particle from penetrating even deeper down into the airways. Alternatively, if more air was required, airways can open up more on account of relaxation.
What is the other name for the tracheobronchial circulation? How much of the cardiac output is reduced by this region of circulations?
Subeouthelial microvascular network. Approx 1-5%
Despite receiving a low cardiac output, how is the tracheobronchial circulatory system well supplied with blood?
Contains extensive branched plus of arteries, capillaries and veins
Where do bronchial arteries branch from?
Aorta, intercostal arteries, other arteries.
How does blood return to the heart from the tracheobronchial circulatory system?
Returns via the systemic and pulmonary veins to both sides of the heart.
Provide six reasons as to why the high perfusion of the tracheobronchial circulatory system is vital,
Efficient gas exchange.
Warming and humidifying of inspired air,
Clearing inflammatory mediators from tissue.
Clearing inhaled xenobiotics.
Supplying airway tissue and lumen with inflammatory cells.
Supplying airway tissue and lumen with proteinaceous plasma.
What is the name of the process that allows the airway tissues and airway lumen to be supplied with proteinaceous plasma?
Plasma exudation
Discuss the effects of the sympathetic and parasympathetic nervous system on the regulation of bronchial smooth muscle and mucus secretion,
Parasympathetic - increased mucus secretion and bronchoconstriction
Sympathetic - decreased mucus secretion and bronchodilation
What neurotransmitter is used for the cholinergic pathway?
Acetylcholine
Discuss the process of neuronal and non neuronal bronchodilation.
Neuronal - release of NO from NOS containing nerves.
Non-neuronal - release of adrenaline from adrenal medulla.
What is the cholinergic reflex and why is it useful?
Refers to the activation of the cholinergic pathway uppon inhaling or ingesting a particle that could become trapped in the airway. Cholinergic activity allows for prompt bronchoconstriction
