Week 8 RM - Respiratory Mucosa Flashcards
What is the structure and function of the mucosa?
Composed of ciliated pseudo stratified epithelia. Cilia are attached to the apical surface of the cells and beat within the airway surface liquid to propel mucous along. Also contains goblet cells which secrete mucus.
What are the three layers of airway mucosa?
Mucosa, submucosa and adventitia
What is the role of the submucosa?
Composed of connective tissue and contains the seromucosal glands which secrete into the lumen.
What is the role of the adventitia?
Outermost layer of connective tissue within the airway which in the upper airways contains the cartilage rings/plates, and in lower airways the smooth muscle.
Where is the airway surface liquid located and what does it do?
It is located on the surface of respiratory epithelium from the trachea to the respiratory bronchioles. It is a thinner liquid that allows the cilia to stand up and beat the mucus along the airways towards the pharynx.
What is the normal thickness of the ASL layer, and what occurs when it is too thin?
Normal thickness is 5-25 micrometers. If too thin, cilia can’t stand up and won’t work. Mucus build up.
What is ASL secreted by?
Glands, serous cells and also plasma squeezed out of capillaries.
What are the three methods of clearing inhaled particles?
Nasal conchae
Mucociliary escalator
Alveolar macrophages
What is the mucociliary escalator?
Transportation of foreign particles from the bronchiole/bronchi/tracheal level of the airways to the pharynx via the work of the cilia
What is the role of alveolar macrophages?
They pass into the alveoli from the pulmonary capillaries and phagocytose particles that have made it past the bronchioles. Destroyed particles delivers to the mucociliary escalator or delivered into the lymphatics
Compare ciliary movement in the trachea with the bronchioles?
2cm per minute in the trachea, 1mm per minute in the bronchioles. Movement in the trachea is 20x faster
What is the underlying pathology in primary ciliary dyskinesia? What are the effects?
Structural defects with the cilia. This causes lack of ciliary function. Stagnant mucus. Recurrent airway infection. Situs inversus (partially or totalis)
What are some things that inhibit alveolar macrophages?
Cigarette smoke Oxidant gases Alveolar hypoxia Corticosteroid Alcohol
What is a major proteolytic enzyme macrophages use to kill bacteria?
Trypsin
Why does cigarette smoke cause damage to the lungs via macrophages?
It kills macrophages, which in turn spill our their granules of proteolytic enzymes which digest away lung tissue.
What is the definition of a Chronic Obstructive Airway Disease? What are the two common types of COAD?
Associated with the narrowing of, or obstruction of the airways.
Chronic Bronchitis and emphysema
What are the three major ways that airways can become obstructed?
Constriction of the smooth muscle surrounding airway
Plugin airway with mucus
Inflammation/swelling of airway mucosa
What other conditions can arise that lead to the narrowing of the airways?
Hyper trophy of mucus glands
Oedema in airway wall
What conditions cause narrowing of airways that arise outside of the airway?
Destruction of lung parenchyma leads to loss of radial traction
Localised compression of the bronchus due to enlarged lymph nodes/neoplasm
Peri bronchial oedema
What is COPD?
Ill defined term related to patients with a mixture of chronic bronchitis and emphysema. Narrowing and inflammation of airways leading to respiratory difficulty
What are the characteristics of chronic bronchitis?
Excessive mucus production and excessive expectoration of mucous
Very common in smokers and people from smoggy cities
What are the two most important factors in the pathogenesis of chronic bronchitis?
Chronic irritation by inhaled substances
Microbiological infection
What changes occur in the airways in chronic bronchitis?
The mucosal layer thickens, goblet cells proliferate.
Submucosal layer thickens greatly, hyper trophy of mucous glands
More mucus is secreted in an attempt to protect the airway from irritants and pathogens, which leads to narrowing
What does the Reid index indicate?
The ratio of the diameter of airway in comparison to the diameter of mucous glands. Hyper trophy of glands common in CB and will deliver abnormal Reid index score.
What changes occur in respiratory bronchioles in chronic bronchitis?
Migration of goblet cells, and production of mucus in small airways where it does not normally occur.
Why does chronic bronchitis have a ‘double threat’ effect on airways?
It has two ways which it narrows. Inflammation of the mucosa and submucosa. Increased mucous within airway.
What is a pink puffer and what are the characteristics of this type of patient?
Usually typical of emphysema patient. Over distension of lungs. Little cough evident. No peripheral oedema. Normal JVP. Normal concentrations of oxygen and CO2. This patient will have a high respiratory rate
What is a blue blaster and what are the characteristics of this patient?
Typical of chronic bronchitis. History of recurrent infections. Frequent cough, sputum. Hypercapnia and cyanosis. Can have peripheral edema
What are some treatment options for CB?
Expectoration of sputum to relieve occluded airways
Increased water intake to decreased mucus viscosity
Nebulising bronchodilators
B2 agonists (may not be effective)
Corticosteroids
What is cystic fibrosis?
Genetic mutation of the CFTR gene which leads to a lack of function of chloride/sodium transport
What are some pulmonary symptoms of CF?
Bronchiectasis: localised irreversible dilation of bronchial tree, chronic purulent sputum expectoration. Airways become floppy and easily occluded
Inflammation of the bronchioles
Where is the CFTR protein found in healthy people?
Epithelial cells in many places, lungs, pancreas, airway mucosa
Apart from chloride transport, what other ion does CFTR influence the movement of?
Sodium
In the lungs, what affect does CFTR have on ENaCs?
Inhibition of sodium movement into cells
Why do CFTR mutations result in thick, viscous mucous?
The absence of functional CFTR leads to decreased inhibition of ENaCs, which cause greater amounts of sodium absorption. This draw water from mucus into cell, following the sodium. This dehydrates the mucus and makes it stickier and more viscous.
Why is the ASL decreased in CF?
Water is drawn away from the ASL layer back into the muscosal cells due to the increased sodium absorption
