Respiratory Pathology Flashcards
Describe Aerogenous spread of invasion to the lungs
Infection reaches the lung as inhaled droplets or larger food particles or fluid. As particle size decreases, increased proportion of particles will pass down the respiratory tract. The bronchiolar-alveolar junction is vulnerable to damage as the total air space area suddenly increases at this point so particles can settle by gravity.
What are the varying defence mechanisms of the zones of the respiratory system?
Conducting - mucus and mucocilliary clearance, antibodies and lyzozyme.
Transitional (bronchioles) - clara cells, antibodies and lyzozyme
Exchange (alveoli) - macrophages, surfactant, antibodies.
Describe Haematogenous Spread of infection to the lungs
The pulmonary capillary bed is very large. Haematongenous lesions tend to localise in caudal lobes - but all lobes can be affected when challenge is high. There is no orientation in the airways.
Describe Transcoelomic spread of infection to the Lungs
Infection via extension from pleura or mediastinum, or traumatic penetration from the chest wall (e.g bite), diaphragm, or oesophagus e.g foreign body.
What is Haemoptysis?
Blood in the saliva or sputum.
Describe Rhinitis and its causes.
Rhinitis and sinusitis often occur together. Rhinitis may be acute or chronic. Aetiologies are infectious, allergic, toxic or traumatic. Within respiratory epithelium are two non ciliated secretory cells, serous cells that secrete clear thin sero mucin and goblet cells that secrete thick opaque mucus.
What is serous rhinitis?
The mildest form - serous cells increase secretion. Early stages of infectious disease, allergy or irritation.
What is catarrhal rhinitis?
Goblet cells and mucous glands now contribute to the secretion. With chronicity there may be goblet cell hyperplasia. May contain white blood cells, exfoliated debris (mucupurulent.)
What is purulent suppurative rhinitis?
This is thicker exudate with many more cells. It is dominated by neutrophils.
What is fibrinous rhinitis?
There is an increase in vascular permeability which allows exudation of fibrinogen which coagulates to fibrin and forms a yellow mat on the affected surface. May be associated with severe underlying ulceration.
Describe granulomatous Rhinitis?
It is macrophage dominated - either specific pathogens or chronic allergic reaction.
Describe Chronic Rhinitis?
Failure to resolve acute rhinitis - chronic rhinitis is typically catarrhal or purulent. In chronic purulent rhinitis there is extensive fibrosis of the lamina propria, atrophy of nasal glands and squamous metaplasia in severe cases. Another feature seen is polypoid thickening of the inflamed nasal mucosa known as nasal polyps. - Round large multiple protuberances into the nasal meatus.
What is Sinusitis?
Often as a sequel or associated with rhinitis. It can also be caused by dental or periodontal disease and penetration of infections from dehorning wounds and fractures of the facial bones. Purulent inflammation of the sinuses is likely to become chronic because of poor drainage.
Describe Viruses that may cause Rhinitis
Common cause of infectious rhinitis - in some fairly specific for nasal mucosa - others cause rhinitis as part of respiratory or more generalised disease. Eg feline calicivirus, canine distemper, parainfluenza, infectious bovine rhinotracheitis, bovine adenovirus, inclusion body rhinitis (porine), swine influenza, equine rhinovirus.
Describe Atrophic Rhinitis in pigs?
Causes atrophy of nasal turbinates and distortion and shorening of the snout. It is caused by co-infection of the nasal mucosa with bordetella bronchiseptica and a toxin producing strain of pasteurella multocida capsular type D. The bordetella appears to facilitate colonisation of nasal epithelium by the toxigenic pasteurella. There is experimental evidence that the toxin acts directly on bone cells of the nasal turbinates to cause bone loss.
Describe Strangles in horses and its potential complications?
Haemolytic streptoocoocci - streptococcus equi, is pathogenic and causes strangles, characterised by suppurative rhinitis, pharyngitis and lymphadenitis of the lymph nodes of the head and neck that drain the URT. Lymph nodes often rupture and discharge pus. Complications can occur such as metastatic abscesses, (bastard strangles), retropharyngeal abscesses can rupture into guttoral pouches and cause chondroid formation, and purpura haemorrhagica can occur - an acute vasculitis - urticaria and extensive oedema of ventrum, head and distal limbs.
What is Glanders?
Caused by burkholderia mallei. It exists in Eastern Europe and Asia. The rhinitis of glanders is characterised by multiple small nodules in the nasal mucosa composed of cores of neutrophils surrounded by a rim of macrophages and granulation tissue. there is fever and head/neck lymphadenitis.
What is mycotic Rhintis?
Aspergillus fumigatus is the commonest cause in the dog - where is also involves the frontal sinus. Infection causes a chronic necrotising inflammation with friable containing necrotic tissue and fungal hyphae. These lesions can be aggressive causing destruction of turbinates and nasal septum.
Describe another cause of mycotic rhinitis?
Cryptococcus neoformans causes a granulomatous rhinitis in cats. Formation of nodules or destructive masses which often result in facial swelling. In severe cases, extension from nasal cavity to involve skin and oral mucosa can occur.
Describe Neoplasia of the Nasal cavity and sinuses
Generally rare entities - can arise from any of the tissues in the region e.g adenoma from glands/epithelium, sarcomas from cartilage, bone, connective tissue. Most are malignant and are usually secondarily infected hence distinguishing severe chronic inflammation and neoplasia can be difficult.
Describe inflammation of the larynx and trachea
Acute inflammation of the airways passes through changes similar to those describe for acute rhinitis. Inflammatory disease involving pharynx, larynx and trachea areas are important because of the potential to obstruct airflow and to cause aspiration pneumonia. Trauma and foreign bodies can cause problems in this area as can masses in the surrounding area which obstruct the airway.
What is laryngeal chondritis?
Cause uncertain but there appears to be a genetic predisposition in short-necked breeds such as texels or southdowns, although any breed can be affected. Causes chronic suppuration within the arytenoid cartilages of the larynx resulting in swelling and occlusion of the lumen.
What is filaroides osleri?
A parasite which forms nodules around the tracheal bifurcation - submucosal nodules (up to 1cm diameter). Associated with a mild chronic inflammatory reaction when the parasites are alive - subsequently, when the parasites die, an intense foreign body reaction develops.
What is tracheal collapse?
Malformations of the trachea that lead to tracheal collapse are important in the dog and occurs principally in miniature dog breeds, also in horses and cattle. The trachea is flattened dorsoventrally with a widened, flaccid dorsal tracheal membrane. Upon inspiration the flaccid membrane is sucked into the tracheal lumen causing obstruction.
What is laryngeal paralysis?
Horses and occasionally dogs develop paralysis of the larynx. It is the most common cause of abnormal respiratory noise (roaring) in horses. It is usually a left sided hemiplegia in horses due to degeneration of the left recurrent laryngeal nerve. Neurogenic atrophy of the left cricoarytenoid muscle causes the left arytenoid cartilage to sag into the laryngeal lumen during inspiration.
Describe Kennel Cough?
This is a common condition characterised pathologically by persistent tracheobronchial inflammation. There can be extension to serous/mucupurulent rhinitis or cranioventral bronchopneumonia. Tonsils and RPLNs are enlarged.
What is chronic bronchitis?
Bronchial irritation and mucus hypersecretion causes a chronic intractable cough. necropsy findings are dominated by excess mucoid or mucopurulent exudate within the trachea and lower airways. The underlying bronchial mucosa is thickened, hyperaemic and oedematous - this is a consequence of increase in size and number of mucus glands, extensive infiltration of the lamina propria by inflammatory cells. Another important feature is smooth muscle hypertrophy in pulmonary arteries can result in pulmonary hypertension - cor pulmonale.
What is bronchiectasis?
This is permanent saccular or cylindrical dilatation of bronchi as a result of the accumulation of exudate within the lumen and partial rupture of the bronchial walls. It usually occurs secondary to chronic bronchitis in which there is a weakening of the bronchial wall. It has a classical appearance characterised by sac like nodules in the lungs which are filled with purulent exudate. Cattle are particularly prone to the development of bronchiectasis due to the combination of complete lobular septation and lack of collateral ventilation.
Describe inflammation of the bronchioles?
Bronchiolar epithelium is highly susceptible to injury due to the presence of clara cells which contain oxidases that can locally generate metabolites that are toxic, and the vulnerability to free radical damage. Bronchioles are much more prone to obstruct when inflamed than bronchi. Bronchiolitis can occur as follows: as an extension of bronchitis or concurrently with bronchitis and pneumonia. Can occur as a distinct entity e.g certain viral infections; pulmonary toxicity.
Describe the structure of Alveoli and their response to injury.
Alveoli have a delicate structure, the type 1 pneumocytes are most susceptible to injury. Irreversible injury results in swelling and sloughing of these cells. As long as the underlying basement membrane remains intact, repair can proceed as a result of type II pneuomocyte division. In severe, diffuse forms of alveolar injury, this process can be so spectacular that the affected tissue can take on the appearance of a gland - alveolar epithelialisation.
What is pneuomonia?
Pneumonia is inflammation that takes place in the alveoli and their walls. Pneumonias can be classified in many ways, such as bronchopneuomina suppurative or fibrinous. Bronchinterstitial, interstitial, granulomatous, embolic.
Describe Bronchopneuomonia?
Inflammation focussed on bronchi, bronchioles and adjacent alveolar lumens. It originates and extends from terminal bronchioles. The most common types are bacterial and mycoplasma infections or aspiration. Suppurative bronchopneumonia will be characterised by neutrophils, cell debris and macrophages within the airway and alveolar lumens.
What is fibrinous bronchopneumonias?
Generally more severe and can cause sudden death due to associated toxaemia. Sometimes also called lobar pneumonia due to involvement of entire lobes and pleural surface. Due to severity, less likely to resolve completely - fibrosis and adehsions.
What is interstitial Pneumonia?
Inflammation that occurs primarily in alveolar walls rather than in alveolar spaces. Lesions in most cases result from blood-borne insult and the damage is often diffuse. Can also occur due to direct aerogenous injury to alveolar epithelial cells. Injury to alveoli may cause protein and fluid exudation and hyaline membrane formation.
describe an example of Interstitial Pneumonia
Fog fever/acute bovine pulmonary emphysema and oedema - usually seen in adult beef cattle in the autumn and is associated with a change in pasture. Underlying pathogenesis is ingestion of L-tryptophan in the pasture which is metabolised to 3-methylindole > bloodstream > lungs.
Describe another example of interstitial pneumonia?
Paraquat poisoning - in dogs and cats - depending on the dose - the lesions range from acute lesions (oedema, haemorrhage, hyaline membranes) - to chronic (fibroplasia of alveolar septae, replacement of alveolar cells with type II cells). Additional extrapulmonary lesions to note following paraquat intoxication are necrosis of the adrenal zona glomerulosa and renal tubular epithelium.
