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Chapter 2. Connective Tissue Proper

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A 7-year-old girl repeatedly sprains her ankles badly. The injuries appear to result during normal play activity. The joints are extremely extensible, and the tendons and skin are unusually flexible. These findings can best be explained by an inherited disorder that affects which of the following protein families?

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A. Actin

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B. Collagen

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C. Elastin

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D. Fibrillin

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E. Keratin

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F. Myosin

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The answer is B: Collagen is a structural protein that ensures strength and minimizes flexibility. If the inherited disease affected collagen, the joints then would be more flexible and, therefore, more prone to injury. Actin, myosin, and fibrillin are proteins found in muscle. Elastin is a connective tissue protein; if it were damaged, the skin would lose flexibility. Keratin is a structural protein of the skin, fingernails, and hair.

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What are the three basic components from which all types of connective tissue are constructed?

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A. Arteries, veins, and capillaries

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B. Cells, fibrous proteins, and ground substance

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C. Collagen, hyaluronic acid, and fibronectin

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D. Fibroblasts, fibroproteins, and proteoglycans

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E. Mast cells, lymphocytes, and adipocytes

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The answer is B: Connective tissues are constructed from cells that are surrounded by extracellular matrix, which consists of fibrous proteins and ground substance.

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Which constituent of connective tissue is most responsible for impeding the movement of pathogens through the lamina propria that underlies epithelia?

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A. Collagen fibers

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B. Ground substance

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C. Mast cells

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D. Plasma cells

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E. Reticular fibers

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The answer is B: Ground substance has a viscous, gel-like consistency, which helps impede invasion by pathogens. Successful pathogens often secrete hydrolytic enzymes, which can reduce the viscosity of extracellular matrix and facilitate spread of the invaders.

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Marfan syndrome results from a genetic mutation in the gene that encodes the protein fibrillin. Patients with Marfan syndrome experience various symptoms, ranging from misalignment of the lens to fatal rupture of the aorta. Which component of connective tissue is most directly responsible for these wide-ranging symptoms?

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A. Collagen fibers

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