Unit 2: Circulatory and respiratory pathology
Basic Cellular Pathology notes · PTU syllabus (BMLS401-18)
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Unit summary
Heart, vessel and lung diseases are major causes of death. This unit covers atheroma, arteriosclerosis, heart block, hypertension and hypotension, upper respiratory infections, bronchial asthma, pneumonia, lung abscess, tuberculosis and lung collapse.
After this unit you can
- Describe atherosclerosis and its complications
- Describe hypertension, hypotension and heart block
- Describe respiratory infections, asthma and pneumonia
- Describe lung abscess, tuberculosis and lung collapse
PTU syllabus topics
- Diseases of blood vessels (atheroma, arteriosclerosis, heart block)
- hyper- and hypotension
- upper respiratory tract infection
- bronchial asthma
- pneumonia
- lung abscess
- tuberculosis
- lung collapse
Organism
Mycobacterium tuberculosis
Commonly Streptococcus pneumoniae
Onset
Slow: weeks of cough, fever, weight loss
Sudden: high fever, productive cough
Key lab tests
Sputum AFB (Z-N), CBNAAT/GeneXpert, culture
Gram stain, sputum and blood culture
Topic 1
Atheroma and arteriosclerosis
- Atherosclerosis: fatty plaques (atheroma) of cholesterol, foam cells and fibrous tissue in the intima of large and medium arteries. Risk factors: high LDL, smoking, hypertension, diabetes, obesity, family history.
- 1Narrowing → angina, claudication
- 2Plaque rupture and thrombosis → myocardial infarction, stroke
- 3Embolism
- 4Weakened wall → aneurysm
- Arteriosclerosis: hardening of arteries, including arteriolosclerosis in hypertension and diabetes. Lab markers of myocardial infarction: cardiac troponin I or T (most specific), CK-MB; lipid profile for risk.
Topic 2
Heart block
- Heart block: delayed or blocked conduction from atria to ventricles. First degree: long PR interval; second degree: some P waves not followed by QRS; third degree (complete): atria and ventricles beat independently — slow pulse, fainting; treated with a pacemaker.
Topic 3
Hypertension and hypotension
Hypertension
Persistent BP of 140/90 mmHg or more
Mostly essential; secondary to kidney disease, Cushing's, phaeochromocytoma; damages heart, brain, kidneys, eyes
Hypotension
BP below about 90/60 mmHg
Blood loss, dehydration, shock, sepsis, adrenal insufficiency; dizziness, fainting
- Lab work-up of hypertension: creatinine, electrolytes, urine protein, glucose, lipids.
Topic 4
Upper respiratory tract infections
- Common cold (rhinovirus), pharyngitis (viral, or group A Streptococcus — throat culture, ASO), sinusitis, otitis media, diphtheria (Corynebacterium diphtheriae), influenza.
Topic 5
Bronchial asthma
- Chronic inflammation causing reversible airway narrowing; triggers — allergens, infections, cold air, exercise. Features: wheeze, cough, breathlessness. Lab: eosinophilia, raised IgE, sputum with Curschmann's spirals and Charcot–Leyden crystals; spirometry and PEFR.
Topic 6
Pneumonia and lung abscess
Community-acquired
S. pneumoniae (commonest), H. influenzae, Mycoplasma, viruses
Sputum Gram stain and culture, blood culture, urinary antigen
Hospital-acquired
Klebsiella, Pseudomonas, S. aureus, Acinetobacter
Culture with susceptibility
Types
Lobar and bronchopneumonia; atypical
Neutrophil leucocytosis, raised CRP and procalcitonin
- Lung abscess: localised pus-filled cavity, often after aspiration (anaerobes) or Staphylococcus; foul sputum; culture including anaerobes.
Topic 7
Tuberculosis
- Mycobacterium tuberculosis spread by droplets; primary TB (Ghon complex) in children; secondary (reactivation) TB with apical cavities. Pathology: caseating granulomas with epithelioid cells and Langhans giant cells.
- Diagnosis: sputum smear (ZN), CBNAAT/Truenat, culture (LJ, MGIT), chest X-ray; ESR raised; Mantoux and IGRA for infection.
Topic 8
Lung collapse (atelectasis)
- Collapse of lung tissue from airway obstruction (mucus plug, tumour, foreign body), compression (pleural effusion, pneumothorax) or loss of surfactant (respiratory distress syndrome in premature babies). Causes hypoxia and predisposes to infection.
Key terms
- Atheroma
- Fatty plaque in an artery wall
- Troponin
- Specific cardiac marker of myocardial injury
- Heart block
- Impaired conduction between atria and ventricles
- Granuloma
- Collection of macrophages and giant cells in chronic inflammation
- Atelectasis
- Collapse of part of a lung
Quick revision
- Atherosclerosis: risk factors, complications, troponin and CK-MB.
- Heart block degrees.
- Hypertension ≥ 140/90; hypotension causes.
- URTIs; asthma features and lab findings.
- Pneumonia types and organisms; lung abscess; TB pathology and diagnosis; atelectasis.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Name three risk factors for atherosclerosis.
- Q2.Which marker is most specific for myocardial infarction?
- Q3.Define hypertension.
- Q4.What are Curschmann's spirals?
- Q5.What is the commonest cause of community-acquired pneumonia?
- Q6.What is a Ghon complex?
Long-answer questions
- Q1.Describe atherosclerosis and its complications.
- Q2.Describe hypertension and its effects.
- Q3.Describe pneumonia and its laboratory diagnosis.
- Q4.Describe the pathology and laboratory diagnosis of tuberculosis.
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