Respiratory pathology 1 Flashcards
What are the functions of airway defence mechanisms?
- filters particles from inhaled air
- prevents particles contacting and damaging epithelial surfaces
- removes particles, inert matter and infectious agents
Which 6 factors/processes are involved in airway defence?
- Aerodynamic filtration
- Mucociliary escalator
- Antibacterial agents
- IgA
- Protective reflexes
- Leucocytes
Describe aerodynamic filtration
- Coiled turbinates leads to turbulence causing particles >10um to impact onto airway mucosa
- Bronchi filter out particles of more than 3um
- Particles ~1-5 um are deposited in the bronchioles + alveoli
Describe the components of the mucociliary escalator
- Upper airways are lined by mucous and cilia
- Layer of mucus, produced by goblet cells, then a thinner layer of aqueous solution which surrounds the cillia, allowing them to beat
What are the functions of mucous?
- Traps and transports particles from the airway to the pharynx
- Prevents dehydration
- Dilutes soluble gases
- Contains antibacterials
Which factors affect the mucociliary carpet function?
- Changes in the viscosity of the mucus: temperature, dehydration, inflammation
- Injury to the epithelium: trauma, infection. chronic irritation
Name the two antibacterial agents involved in airway defence
Lysozyme
Lactoferrin
What is lysozyme?
Bacteriolytic protein that hydrolyses peptidoglycan
What is lactoferrin?
Iron binding protein synthesised by neutrophils and epithelial cells which stops bacterial and fungal growth
Name the main immunoglobulin found in airways, what is its function?
IgA
Precipitates antigens causing them to be phagocytosed by leucocytes
Give 2 examples of protective reflexes
Cough
Sneeze
Describe the role of macrophages in airway defence
- Alveolar, Interstitial, Intravascular
- Phagocytose particles + agents.
- Recruit neutrophils
- Coordinate inflm
- Ascend mucociliary escalator
Clinical case: 12 week old kitten with a upper respiratory tract viral infection
What effect might the viral infection have on the respiratory defence mechanisms?
Viral damage can cause damage to the mucociliary escalator
Leads to a secondary bacterial infection
A secondary bacterial infection can be seen grossly by?
Pus
Viral infection of respiratory epithelial cells leads to …?
Impaired function
Cell death
Inflammation
Give 3 developmental abnormalities of the upper airways
- Cleft palate
- Guttural pouch tympany
- Brachycephalic airway syndrome
How is a cleft palate caused?
Failure of the palatine shelves to close
Describe guttural pouch tympany
- Nasopharyngeal opening defect => air in guttural pouch.
- Pressure => dyspnoea, dysphagia + aspiration pneumonia
Brachycephalic airway syndrome is a combination of which 3 anatomical problems?
- Stenotic nares
- Everted laryngeal saccules
- Elongated soft palate
What is epistaxis?
Bleeding from the nose
What are some causes of epistaxis?
- Inflammation
- Infection, trauma
- Neoplasia
- Clotting defects
What are the 5 typical signs of inflammation?
- Redness
- Swelling
- Heat
- Pain
- Loss of function
How does the type of exudate change as inflammation progresses?
Serous => catarrhal => purulent
- can also become fibrinous after catarrhal
What are the signs of acute inflammation?
Vasodynamic changes – redness, swelling, exudate
Increased secretions – serous, mucus
Describe the following types of exudate: Serous Catarrhal Fibrinous Purulent
- Clear watery discharge
- Viscoid, mucoid
- Thick, fibrinous, haemorrhagic
- Thick, white, green, brown
Which type of exudate contains some inflammatory cells but in low levels?
Catarrhal
Which type of exudate contains high numbers of inflammatory cells?
Purulent
Which pathological changes are associated with chronic inflammation?
- Mucosal hyperplasia
- Epithelial metaplasia
- Increased numbers of macrophages, lymphocytes and plasma cells
- Fibroblasts
How does the shape of epithelial cells change in metaplasia secondary to chronic inflammation?
Ciliated columnar => stratified squamous
Polyps secondary to chronic inflammation occur most commonly in which species?
Horses and cats
Where is the respiratory tract to polyps arise in cats?
Auditory tube or tympanic bulla
What are polyps?
Lumps of fibrous material and blood vessels, coated in epithelium that get in the way of airway flow
What are some causes of upper airway inflammation?
- Irritants/allergens
- Foreign bodies
- Parasites
- Infectious agents
An infectious disease is the combination of which 3 factors?
Aetiological agents
Susceptible host
Favourable environment
Give examples of viral agents associated with inflammation of the upper respiratory tract
- Bovine herpes virus 1
- Equine herpes virus 1 and 4
- Equine influenza virus
- Feline calicivirus
- Canine distemper virus
- Canine adenovirus
Bovine herpes virus cases what respiratory condition?
Infectious bovine Rhinotracheitis
What can exacerbate Infectious bovine rhinotracheitis?
Overcrowding, stress
How does Infectious bovine Rhinotracheitis affect the respiratory system, describe the different stages of infection/damage?
- Damage to mucociliary escalator
- Impaired mucosal defences
- Secondary bacterial infection
- Influx of neutrophils, purulent discharge
- neutralising antibodies and cell mediated immunity response
- resolution of viral and bacterial infection
What is the trigger for an inflammatory response in an infectious bovine tracheitis infection?
Infection of nasal and conjunctival epithelial cells where viral replication takes place
What are the signs of infectious bovine tracheitis infection?
- Serous or catarrhal exudate from nose which worsens to purulent discharge
- Conjunctival and nasal hyperaemia
Give two examples of bacterial agents associated with inflammation of the upper respiratory tract
Streptococcus equi in horses
Pasteurella multocidi in pigs
Which disease is caused by Streptococcus equi?
Strangles
Which exudate is typical of S.equi?
Initial serous nasal discharge becomes purulent
Describe how a S.equi infection causes damage?
- colonises nasopharyngeal mucosa
- lymphatic spread to lymph nodes
- abscesses within parotid lymph node can rupture
- guttural pouch emphysema
Why do abscesses rupture into the guttural pouch in horses?
It is the direction of least resistance
Which fungal agent is associated with inflammation of the upper respiratory tract?
Aspergillus fumigatis
Describe an Aspergillus fumigatis infection
- Dogs, horses and birds
- Fibronecrotic/granulomatous inflammation
- Bone lysis
- Guttural pouch mycosis
Describe guttural pouch mycosis and its associated complications
- Infection causes severe inflammation and necrosis
- Causes damage to cranial nerves which can lead to facial paralysis
- Erosion of blood vessels which can cause fatal haemorrhage
Name the neoplasia associated with the following tissues:
- Lining epithelium
- Glands
- Bone
- Connective tissue
- Squamous cell carcinoma
- Adenocarcinoma
- Osteosarcoma
- Fibrosarcoma
