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. Histologic findings from a section of the left ventricle are shown below. The type of collagen seen in the autopsy sample is most likely to be extensively found in which of the following normal body tissues?

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.  Histologic findings from a section of the left ventricle are shown below.  The type of collagen seen in the autopsy sample is most likely to be extensively found in which of the following normal body tissues?

Quizplus · Accepted Answer

11ec160b_378a_1410_9249_81db0417ce69_MD0001_00 Evolution of a myocardial infarction occurs in several stages. The final stage of the healing process begins approximately 2 weeks after infarction and involves increased deposition of type I collagen. Fibrosis continues until about 2 months after infarction, resulting in a dense collagenous scar composed primarily of type I collagen. The scar can be identified grossly as a firm, gray-white lesion or microscopically as collagenous tissue replacing myocardium (as in this patient). In addition to its role in wound healing, type I collagen (the most abundant type) provides strength and support for a variety of cellular tissues and organs (eg, tendons, ligaments, skin). It is also the major organic component in bones and significantly contributes to overall bone strength. Defects in type I collagen can occur in osteogenesis imperfecta, an autosomal dominant disorder that may present with fragile bones and ligament laxity. (Choices A, C, and D) Basement membrane contains type IV collagen; hyaline cartilage (eg, articular surfaces) and nucleus pulposus contain type II collagen. (Choice B) Granulation tissue is a capillary-rich fibroblastic proliferation composed primarily of type III collagen. Although granulation tissue is seen approximately 7 days after an acute myocardial infarction, it is eventually replaced by type I collagen as the infarct heals. Type III collagen is involved in the structural maintenance of extensible connective tissues and is often found alongside type I collagen. Educational objective: Type I collagen is the primary collagen in mature scars (eg, remote myocardial infarction). It is the most prevalent type of collagen and provides strength and support throughout the human body, particularly in bones, tendons, ligaments, and skin.

A 67-Year-Old Man Is Found Dead in His Home