Question

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 he had a myocardial infarction a year ago. An autopsy is performed. Gross examination of the heart shows white scarring and enlargement of the left ventricle.

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: Tendon

Approach to the Question:

Myocardial Infarction
⬇
⚙️ Cardiomyocyte Necrosis → Inflammation (↑ Cytokines)
⬇
⚙️ Removal of Dead Cells → Granulation Tissue Formation (Type III Collagen)
⬇
⚙️ Maturation of Granulation Tissue → Replacement with Type I Collagen
⬇
White Scarring in Heart Contains Type I Collagen (Similar to Tendons)

Think Like This:

1. Myocardial Infarction = A house collapses 🏚️ (cardiomyocyte death).

2. Granulation Tissue = Temporary scaffolding 🏕️ to stabilize the site.

3. Mature Scar = Permanent rebuild with concrete and steel 🏠 (Type I Collagen).

🧠 Healing Process Post-MI 

⬇
⚙️ Acute Myocardial Infarction → Cardiomyocyte Death
⬇
🔍 Necrosis Triggers Inflammation

Analogy: Think of a fire 🔥 that needs extinguishing (immune cells act as firefighters).
⬇
⚙️ Macrophage Activation → Removal of Necrotic Tissue
⬇
⚙️ Granulation Tissue Formation

Type III Collagen as Scaffold (temporary framework, flexible like a tent 🏕️).
⬇
⚙️ Fibroblast Activation → Deposition of Type I Collagen

Type I Collagen for Strength (like concrete replacing a tent structure).
⬇
🧠 Mature Scar (White Scarring in LV) Contains Type I Collagen

Key Insights for Diagnostic Reasoning

⚖️ Differentiating Collagen Types Using Analogies

Type I Collagen

• Found in Tendons, Bone, Ligaments, Skin, Mature Scars.

• Analogy: Think of it as steel cables—providing strong tensile strength.

Type III Collagen

• Found in Granulation Tissue, Blood Vessels, Embryonic Tissue.

• Analogy: Like scaffolding—flexible but temporary.

Explanation of Other Answers

🧠 Basement Membrane (Type IV Collagen)

• Acts as a filtering net in epithelia and endothelium.

• ⚖️ No role in scar formation or tensile strength.

🧠 Hyaline Cartilage (Type II Collagen)

• Provides structural support in cartilage.

• ⚖️ Think of it as a shock absorber in joints—irrelevant to scars.

🧠 Nucleus Pulposus (Type II Collagen)

• Gel-like center of intervertebral discs.

• ⚖️ Think of it as a cushion in the spine—not involved in myocardial repair.

🧠 Granulation Tissue (Type III Collagen)

• Early wound healing contains Type III Collagen.

• ⚖️ Replaced by Type I Collagen in mature scars—no longer present in healed tissue.

🧠 Tendon (Type I Collagen)

• Shares the same collagen type as mature scars (Type I).

• ⚖️ Correct Answer: Strong tensile properties match the composition of myocardial scars.

Flashcards

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Dr. Shoaib Ahmad