Pathology of Respiratory Tract Infections Flashcards
What are different kinds of microorganisms in terms of pathogenecity?
Primary, Facultative, and Opportunistic
What are primary microorganisms?
Can establish an infection in almost anyone
What are facultative microorganisms?
Requires defences to be reduced a little bit to cause disease
What are opportunistic microorganisms?
Not very infectious, do not have pathogenic properties to invade human tissue, but if defences are dropped then they can cause a clinically evident infection
What does the ability to resist infection depend on?
- State of the host defence mechanism
- Age of patient
What are some upper respiratory tract infections?
Coryza (common cold) Sore throat syndrome Acute laryngotracheobronchitis (coup) Laryngitis Sinusitis Acute epiglottitis
What is acute epiglottitiis commonly caused by?
- Group A beta haemolytic streptococci
- Haemophilus influenza
Who seems to be most prone to acute epiglottitis?
Young Children
What are some examples of lower respiratory tract infections?
Bronchitis
Bronchiolitis
Pneumonia
What is pneumonia?
Acute inflammatory process in the alveoli
What are some respiratory tract defence mechanisms?
- Macrophage-mucociliary escalator system
- General immune system
- Respiratory secretions
- Upper respiratory tract as a filter
What is the macrophage-mucociliary escalator system composed of?
- Alveolar macrophages
- Mucociliary Escalator
- Cough Reflex
How does the upper respiratory tract help to prevent the lower respiratory tract from becoming infected?
Warms and humidifies air, supplying a large surface area where material in the air may be deposited so it does not reach the lower respiratory tract
How are particles cleared from the lungs?
Macrophage-mucociliary escalator:
1) Macrophages clear particles by phagocytosis
2) Leave via the mucociliary escalator or through lymph
What can we ask when considering why the defences are failing?
Local bronchial obstruction (tumour, foreign body)?
Local pulmonary damage (bronchiectasis)?
Generalised lung disease (cystic fibrosis, COPD)?
Non-respiratory disease (immunocompromised, aspiration)?
What are opportunistic infections?
Infections by organisms not normally capable of producing disease in patients with intact lung defences
What are some examples of opportunistic pathogens?
Low grade bacterial pathogens
Cytomegalovirus (CMV)
Pneumocystis jirovecii
Other fungi and yeasts
2 types of airflow are
laminar or turbulent
What is laminar flow?
Ordered flow
What is turbulent flow?
Random or chaotic flow
What does bulk flow depend on?
Pressure difference
What occurs beyond the terminal bronchiole?
Diffusion
What barrier is present in the alveoli?
Blood-air barrier
What are 4 abnormal states associated with hypoxemia?
Ventilation/perfusion imbalance (V/Q)
Diffusion impairment
Alveolar hypoventilation
Shunt
