MCQ 2: USMLE: Cardiovascular System (Myopericardial disease)

A 67-year-old man is found dead in his home. The cause of death is not apparent. He had a long history of hypertension and a prior myocardial infarction one year ago. An autopsy is performed. Gross examination of the heart shows white scarring and enlargement of the left ventricle. Histologic examination of the left ventricle shows dense collagen deposition replacing normal myocardium.

👉 Question:

The type of collagen seen in the autopsy sample is most likely to be extensively found in which of the following normal body tissues?

A. Basement membrane

B. Granulation tissue

C. Hyaline cartilage

D. Nucleus pulposus

E. Tendon

✅ Correct Answer:

E. Tendon

📚 Explanation:

This patient died with evidence of an old myocardial infarction characterized by fibrotic scarring of the myocardium. Histology shows dense type I collagen deposition replacing necrotic cardiac tissue during infarct healing.

💉 Pathophysiology of Myocardial Infarction Healing:

• Acute inflammation with neutrophil infiltration within the first few days.
• By the end of the first week, granulation tissue rich in capillaries and type III collagen forms.
• Over subsequent weeks, type III collagen is replaced by type I collagen.
• By 2 months, infarcted region becomes a dense, fibrotic scar (gray-white grossly).

🧬 Collagen Subtypes:

Type	Locations	Associated Diseases
I	Skin, bone, tendons, ligaments, dentin, cornea, blood vessels, scar tissue	Osteogenesis imperfecta
II	Cartilage, vitreous humor, nucleus pulposus	Skeletal dysplasias
III	Skin, lungs, intestines, blood vessels, bone marrow, lymphatics, granulation tissue	Ehlers–Danlos syndrome (Type IV)
IV	Basement membrane	Alport syndrome

🧠 Key Concept:

Type I collagen is the most abundant collagen in the body providing tensile strength. Found in tendons, ligaments, skin, bone, and mature scar tissue. In myocardial infarction, type I collagen replaces damaged myocardium forming a firm scar.

❌ Why Other Options Are Incorrect:

• A. Basement membrane – Contains type IV collagen; defective in Alport syndrome.
• B. Granulation tissue – Contains type III collagen (immature collagen) before replacement by type I collagen.
• C. Hyaline cartilage – Contains type II collagen.
• D. Nucleus pulposus – Contains type II collagen.

🧩 High-Yield Points:

• Type I collagen = main component of mature scars (e.g., healed MI).
• Provides tensile strength in tendons, ligaments, skin, and bone.
• MI healing: type III → type I collagen transition.
• Osteogenesis imperfecta = defective type I collagen synthesis.

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