Pulmonary Pathology Flashcards
Describe the gross anatomy of the lung
Normal Lung (images):
- Gross photograph of normal lungs and heart
- Pleural surface is smooth and shiny
- Lungs extend down to the apex of the heart
- Cut surface of normal lung
Describe the anatomy of the trachea
- Connects upper respiratory tract to lungs via bronchial tree
- 15-20 C-shaped incomplete cartilage rings
- Hyaline cartilage
- Posterior wall fibrous tissue
- Ciliated pseudostratified columnar epithelium
- Goblet cells (mucus producing) - Smooth muscle
Describe the anatomy of the bronchi
- Ciliated pseudostratified columnar epithelium
- Goblet cells (mucus producing) - Smooth muscle
- Hyaline cartilage
Describe the anatomy of the bronchioles
- Ciliated simple columnar and cuboidal epithelium
- Club cells
- Smooth muscle
- Elastic fibres
- <1mm in diameter
- Cartilage disappears at size <0.6mm - Terminal bronchioles supported by smooth muscle cells
- Distal to each terminal bronchiole is acinus
Describe the anatomy of the alveoli
- Respiratory zone starts at respiratory bronchiole -> consist of millions of alveoli
Alveoli consist of
Type I and type II cells
- Type I pneumocytes (squamous epithelium) (95%)
- Type II pneumocytes (cuboidal epithelium, surfactant producing – protects alveoli from collapse during expiration)
Describe the anatomy of oxygen exchange
What are the five major groups of lung disease?
Obstructive Lung Diseases
:
- Chronic bronchitis
- Emphysema
- Asthma
Restrictive Lung Diseases:
- Acute Respiratory Distress Syndrome
- Silicosis
Infective Lung Diseases
:
- Pneumococcal lung infection
- Tuberculosis
Vascular Lung Diseases
Neoplastic Lung Diseases
Describe obstructive lung disease
- Increase in resistance to airflow due to partial or complete obstruction of the airways
- Airway obstruction is worse with expiration -> decreased expiratory flow rate -> more force is required to expire a given volume of air, or emptying of lungs is slowed
- FEV1 to FVC ratio is characteristically decreased -> FEV1/FVC is ≤ 70% in adults and < 85% in children
Describe restrictive lung disease
- Refer to intrinsic lung diseases that are restrictive (limited potential of lungto expand)
- Exclude other processes which limit lung expansion:
- Chest wall abnormalities
- Neuromuscular disease
- Large abdominal masses
- Lung function test shows reduced compliance, reduced TLC, FVC and FEV1
- Patients develop symptoms of progressive breathlessness and cough
What is the difference between obstructive and restrictive lung diseases?
- Obstructive lung disease makes it hard to exhale all the air in the lungs.
- People with restrictive lung disease have difficulty fully expanding their lungs with air
Differences in spirometry
What are the main characteristics and anatomy/histology of chronic bronchitis (Obstructive lung disease)?
- Clinical definition: cough with sputum production ≥ 3 months in at least 2 consecutive years
- Aetiology: cigarette smoking
Types:
1)Simple chronic bronchitis:
- productive cough (no airflow obstruction)
2) Chronic asthmatic bronchitis:
- cough, intermittent bronchospasm and wheezing
3) Chronic obstructive bronchitis:
- cough and outflow obstruction
Pathogenesis
1.Hypertrophy of submucosal mucus glands (trachea and main bronchi)
2.Hyperplasia of mucin-secreting goblet cells (smaller bronchi and bronchioles)
=> Hypersecretion of mucus -> mucous plugging & overproduction of sputum
What are the main characteristics and anatomy/histology of emphysema (Obstructive lung disease)?
- Damages and enlarges the alveoli in the lungs
- Most common cause is smoking, rarely congenital condition known as α1-antitrypsin deficiency - Dyspnea: Problems with exhalation -> shortness of breath and cough
Image: Both lungs are markedly enlarged; arrows indicate clusters of dilated air spaces which are conspicuous in the middle and lower lobes of the right lung and the lower lobe of the left lung
- Permanent dilation of air spaces distal to terminal bronchioles
- Destruction of alveolar walls -> loss of elastic
recoil -> obstruction
- Asymptomatic until > 1/3 lung parenchyma is destroyed
- Can affect airways before distal alveoli, airways distal to terminal bronchioles, distal acinus
What are the differences between chronic bronchitis and emphysema?
What are the main characteristics and anatomy/histology of asthma (Obstructive lung disease)?
- A chronic inflammatory disorder of the airways -> hyper-reactive airways
- Recurrent episodes of wheezing, breathlessness, chest tightness and cough caused by bronchospasm (reversible)
- Status asthmaticus: severe condition in which asthma attacks follow one another without pause (severe and prolonged symptom; rare) -> can be fatal
- Extrinsic asthma - type I hypersensitivity reaction induced by an extrinsic allergen (producing too much IgE)
- Intrinsic asthma - non-immunological e.g. ingestion of aspirin; pulmonary viral infections, cold, exercise and stress
What are the main characteristics and anatomy/histology of acute respiratory distress syndrome (ARDS) (restrictive lung disease)?
- Not a specific disease
- Common causes: infection, burns, gas inhalation - ARDS is caused by protein-rich pulmonary
edema -> causes severe hypoxemia and impaired carbon dioxide excretion
- Syndrome of acute respiratory failure -> Rapid onset of respiratory distress (dyspnoea, tachypnoea & distress) - Diffuse alveolar capillary & epithelial damage
- Leakage of proteins and fibrin into
alveoli -> hyaline membranes - Life-threatening condition that occurs when there is severe fluid buildup in both lungs
- Some alveoli fill with fluid, others collapse -> lungs can no longer fill properly with air and they become stiff - Can be fatal within a few days (or lung damage with fibrosis)
Describe the pathogenesis of ARDS?
Acute phase (first 1–6 days):
- Sloughing of the bronchial and alveolar epithelial cells
- Neutrophils
- Air space filled with protein rich edema fluid
- Lung injury caused primarily by neutrophil-dependent and platelet-dependent damage to the endothelial and epithelial barriers of the lung
- Resolution delayed due to injury to the lung epithelial barrier
- prevents removal of alveolar edema fluid
- deprives lung of adequate quantities of surfactant
Sub-Acute phase (next 7-14 days):
- Some of the edema has usually been reabsorbed
- Evidence of attempts at repair with proliferation of alveolar epithelial type II cells
- May also be fibroblast infiltration and some collagen deposition
Chronic phase (after 14 days):
- Resolution of the acute neutrophilic infiltrate
- More mononuclear cells and alveolar macrophages in the alveoli
- Often more fibrosis with ongoing evidence of alveolar epithelial repair
Outcome: In many patients, resolution without fibrosis and gradual resolution of the edema and acute inflammation
Describe the anatomy and histology of lobar pneumonia (lobar topography) and the types of hepatisation
- Acute exudative inflammation of an entire pulmonary lobe
- Lobe enlargement
- Loss of spongy appearance
- Hepatization (conversion of tissue (as of the lungs in pneumonia) into a substance which resembles liver tissue and may become solidified) stops abruptly at the fissure
- Red hepatization: Early exudate is full of bacteria, RBC, neutrophils, fibrin
- Grey hepatization: Later exudate contains macrophages, broken down RBC, debris
Describe the anatomy and histology of bronchopnuemonia (lobular (plural) topography)
- Affects one or more lobes
- Suppurative peribronchiolar inflammation - Multiple foci of condensation (1-3 cm diameter, white-yellowish, imprecisely circumscribed)
Histology:
- Multiple small foci of inflammation
- Extensive congestion and dilation of blood vessels and areas of poorly circumscribed consolidation
- Areas of inflammation are separated by areas of normal lung parenchyma
What are the histological changes of lobar pneumonia during the different stages of the disease?
- Congestion: Alveolar lumen fills with serous exudate (rare leucocytes), bacteria
- Red Hepatisation: Exudate fills with erythrocytes (cause of red appearance) and leukocytes
- Gray Hepatisation: Red blood cells breakdown (causing loss of red appearance) and exudate fills with macrophages
- Resolution: exudate within the alveolar spaces drains
Describe tuberculosis (TB)
- A chronic pneumonia caused byMycobacterium tuberculosis
- Presence of granulomatous inflammation
- Centres of tubercular granulomas undergocaseous necrosis
- Usually involves the lungs
Primary tuberculosis:
- Develops in a previously unexposed, and therefore unsensitized, person
- Mainly asymptomatic -> latent phase
- ~ 5% develop clinically significant disease -> progressive TB
Secondary tuberculosis:
- Reactivation of dormant primary lesions many decades after initial infection
- Secondary TB – may be asymptomatic or with “afternoon” fever & night sweat, malaise, anorexia & weight loss
Describe the Ghon complex in tuberculosis
- The Ghon complexis the pathognomonic macroscopical lesion of primary pulmonary tuberculosis after initial infection in children
- The Ghon focus
- Lymphadenitis
- Lymphangitis
- Ghon focus consist of a calcified focus of infection and an associated lymph node
Describe miliary tuberculosis
- ~5% progressive primary TB
- Mycobacterium tuberculosis can enter circulation via pulmonary vein -> can infect other organs (liver, spleen etc.)
- TB in organ ->cell-mediated immune response activated
- Infected sites become surrounded by macrophages -> form granuloma (give the typical appearance of Miliary tuberculosis)
