Respiratory Flashcards
What five defence mechanisms are utilised in the airway?
- Aerodynamic filtration
- Mucociliary escalator
- Antibacterials
- IgA
- Protective reflexes
Describe the two mechanisms of aerodynamic filtration in the airways.
- Coiled turbinates cause particles >10nm to impact with airway mucosa
- Branched and tortuous bronchi filter out particles >3um (any less than this are deposited in bronchioles and alveoli.
What is the mucociliary escalator?
The epithelium of the respiratory tract contains ciliated epi cells and goblet cells. Mucous produced by goblet cells is swept in an oral direction by the cilia and is reswallowed by the animal.
What is the function of mucus in the respiratory tract?
- Mucociliary escalator (traps and transports particles to the pharynx)
- Physical barrier
- Prevents dehydration of mucosal epi
- Dilutes soluble gases
- Contains anti-bacterials
Name and describe the antimicrobial substances present in the mucous.
- Lactoferrin - Fe binding protein synthesized by neutrophils and epi cells - causes retardation of bact and fungal growth
- Lysozyme - Hydrolyses peptioglycan and key cell wall protein of g+ve bacteria
Which two factors affect the mucociliary carpet function?
What causes them?
- Changes in mucus viscosity - due to temperature, dehydration and inflammation.
- Epithelial injury - due to trauma, infection and chronic irritation (causes epi metaplasia)
What does this picture depict?
Describe.
Epithelial metaplasia. An abnormal change in the nature of a tissue (ie cell type to a stratified squamous appearance) in response to a stimuli (here chronic irritation)
This is a reversible change, once the stimuli is removed and the cells turned over the native cells return.
Which Ig is the main type found in the airways?
IgA
What protective reflexes are airway motivated?
Why are they vital?
Cough and sneeze
These are the reserve clearance mechanisms and are particularly vital during situations such as those when the ciliated cells are lost (becomes only mechanism)
Describe the alveolar defences found in the LRT.
Macrophages: Three types
- Alveolar
- Interstitial
- Intravascular
These phagocytose particles and agents, recruit neutrophils, co-ordinate inflammation and ascend the mucociliary escalator
Describe the mechanisms of action of the of macrophages found in the alveoli.
- Alveolar - ingest pathogens and particles, then MO move to the bronchi and are removed by the mucrociliary escalator. Also secrete chemokines which attract neutrophils during inflammation.
- Interstitial - Reside within alveolar interstitial tissue and act to phagocytose particles that have traversed alveolar cells. They enter the bronchiolar/bronchial lymphatics and move to pulmonary or tracheobronchial lymph nodes.
- Intravascular - Only found in some species (ruminants, pig, cat) and attach to the lumenal surface of capillary endothelial cells & act like Kupffer cells in the liver to clear particulate matter from the blood (e.g. small emboli).
Describe this lesion.
A cleft palate
Failure to close the palatine shelves (primary or secondary palate) causes aspiration of food at weaning and beyond
What is seen here? What problems can this pathology cause?
GP tympany (air build up)
A defect of the nasopharyngeal opening causes (unilateral) trapping of air and mucus in the GP.
Oesophageal pressure can lead to dysphagia and dyspnoea.
Can lead to aspiration of food and pneumonia and predisposes horses to GP bacterial infection
Describe the problems associated with Brachiocephalic airways.
- Stenotic nares
- Everted laryngeal saccules
- Elongated soft palate
Leads to airway obstruction, cyanosis and syncope
Epistaxis
Bleeding from the nose
What can cause bleeding from the URT?
- Inflm
- Infection
- Trauma
- Neoplasia
- Clotting defects
What is the difference between active and passive congestion of the URT?
- Active is caused by inflammation
- Passive is caused by reduced blood outflow
What are the cardinal signs of inflammation?
- Redness
- Swelling
- Loss of function
- Pain
- Heat
What stages of acute inflammation characterise types of nasal discharge?
Describe each stage
- Serous - clear, watery
- mucosal hyperaemia and oedema, increased fluid production
- Catarrhal - thick - mucoid/ creamy white
- Increased mucoserous secretions, some inflammatory cells
- +/- Fibrinous - tacky yellow red deposits
- Increased vascular permeability +/- necrosis
- Purulent - thick, white, green, brown
- Filled with degenerating neutrophils
What are the common pathological changes in the URT with chronic inflammation?
- Mucosal hyperplasia of epithelium and seromucous glands
- Epithelial metaplasia from ciliated columnar to stratified squamous
- Chronic inflammatory cells infiltrate - mo, l, plasma cells
- Fibroplasia
Polipoid thickening
Abnormal thickening/ growth of tissue projecting from a mucous membrane .
It is pedunculated if attached to the mucosa by an elongated stalk. If no stalk is present it is sessile.
Polypoid thickening is characteristic of chronic nasal inflammation particularly in which species and where?
Horses - they arise in the ethmoid region
Cats - they arise from the auditory tubes or tympanic bulla (may extend into the pharynx or external auditory tubes
Causes of URT inflammation.
- Irritants/ allergens eg pollen
- FB/ trauma
- Parasites - oestrus ovis
- Dental disease
- Infectious agents - viral, bacterial and fungal
Name three examples of viral agents associated with URT infections
- Infectious bovine rhinotracheitis virus (IBR) - HV1
- Equine herpes virus 1 + 4
- Equine influenza virus
- Feline herpes virus 1 Flu
- Feline calicivirus Flu
- Canine distemper virus
- Canine adenovirus 2
- Canine parainfluenza virus
IBR is an example of which type of herpes virus?
1
What environmental factors lead to increased susceptibility to IBR?
Stress and overcrowding
Describe the transmission and pathogenesis of IBR
Aerosol transmission
- Nasal mucosa and conjunctiva are infected
- Viral replication in epithelial cells +/- dissemination throughout respiratory tree
- Inflammatory response leads to conjunctival and nasal hyperaemia and a serous/catarrhal exudate
- Damages mucociliary escalator impairs immune response = secondary bacterial infection = purulent nasal discharge
Describe this lesion and suggest a viral cause.
A tacky yellow-red substance is adhered to the nasal cavity wall throughout the nasal cavity. Underneath the mucosa is diffusely redened.
Diffuse acute fibrinonecrotising inflammation of the nasal cavity.
After how many days are antibodies produced in an IBR infection?
10-14 days
Describe the pathogenesis of S, equi var equi in the horse.
Aerosol/ fomite transmission
- Colonisation of the NP mucosa
- Serous -> purulent nasal discharge
- Lymphatic spread of the bacteria causes lymphatic abscessation
- Gutteral pouch empyema caused by in-bursting of abscesses
Describe the pathogenic features of Pasteurella multocida in pigs.
Seen around 4-12 weeks
Preinfection with BB necessary, environmental and nutritional factors also instigate
Moderate to severe atrophy of nasal turbinates associated with distortion/ shortening of the snout
What structures contained within the GP can be damaged in guttural pouch mycosis?
What clinical signs can be signs?
Cranial nerve damage (VII) - Facial muscle, tongue, pharynx and larynx paralysis
Internal carotid atery - Potentially fatal haemorrhage
What is the common aetiological agent in Guttural Pouch mycosis in the horse?
This fungi is also implicated in which type of aspergillosis in the dog? Describe.
Apergillus fumigatus
- Severe fibrinonecrotic inflammation
- Usually unilateral
Nasal aspergillosis
- Forms visible fungal plaques on nasal mucosa causing fibrinonecrotic to granulomatous inflammatory response
- mucopurulent to haemorrhagic nasal discharge.
- Can lead to turbinate destruction.
Upper airway neoplasia is most common in which categories of dog?
Are they usually malignant or benign?
Middle-aged to elderly animals. Breeds with increased risk include; airedales, bassets, OESD, german SH pointers
They are usually malinant (>80%)
Describe this lesion
Multifocal round to oval raised tacky white nodules present in the guttural pouch of this horse. Varying in size from 0.5x0.5 cm to 1-0.5cm. The rim of the nodules is focally redened.
Moderate, multifocal fibrinonecrotising ginflammation of the guttural pouch mucosa. Associated with guttural pouch mycosis caused by Aspergillus fumigatis
Describe this lesion
A large (30x20 cm) focal pale red infiltrating mass is found in the nasal cavity of this horse. Externally it distorts the normal anatomy of the face and extends from the upper eyeline to about 10cm below the eyeline on the left of the face. Externally three ulcerated raised masses are seen (3x3cm)
Severe chronic? squamous cell carcinoma
In which breeds is tracheal hypoplasia likely to be seen?
What clinical signs can be seen?
Why?
Pekinese, english bull terrier/ bulldog.
Causes exercise intolerence and dyspnoea.
Resistence in the tube is inversely proportional to the radius (/diameter) of said tube. Therefore a small decrease in tube diameter leads to a large increase in tube resistence.
Describe the effects of a dorsoventrally flattened trachea in the dog.
DV flattening of the trachea can often lead to prolapse of the dorsal membrane of the trachea (increasing tube resistence)
This leads to dyspnoea and increase respiratory noise. May lead to separation of the dorsal ligament and mucosa from cartilage in severe cases.
True or false
Laryngeal paralysis in the dog is often bilateral.
How does this differ in the horse and why?
True
In the horse the paralysis is often unilateral on the left side, the large tortuous path of the left recurrent laryngeal nerve leaves it prone to damage.
What is abnormal in this picture of the larynx?
What pathology and clinical signs are associated?
Unilateral atrophy of the left cricoarytenoid muscles, associate with paralysis of the left recurrent laryngeal nerve.
Atrophy/ paralysis of these muscles leads to failure/ partial abduction of the arytenoid cartilages of the larynx at inspiration.
(Exercise intolerence) and increased respiratory noise (roaring)
What are the five common causes of laryngeal oedema?
Describe the gross path findings in this case.
- Local trauma eg. intubation
- Irritants eg. smoke
- Acute respiratory infections
- Laryngeal chondritis
- Anaphylaxis/allergic reactions
Moderate acute diffuse laryngeal oedema. Diffuse redening and swelling of the entire larynx is seen causing constriction of the laryngeal opening.
Describe this lesion.
Multifocal redening of the tracheitis is seen here covering approximately 50-60% of the tracheal mucosa. Similar lesions also seen in the larynx (approximately 20%). The ulcerative lesions range from dark to pale red and are soft in texture.
Severe acute multifocal serous ulcerative tracheitis
What are the four main causes of laryngeal hemiplegia?
- Primary neuronal degeneration
- Congenital neuronal abnormality
- Neurotoxins eg lead
- Secondary compression of the nerve - GP disease, neoplasia, cervical trauma etc
How does laryngeal paralysis occur?
Damage to the recurrent laryngeal nerve.
This causes atrophy of the cricoarytenoid muscle
Leads to failure of the arytenoid cartilages to abduct on inspiration