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Chapter 24: Venous and Lymphatic Disease

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All of the following regarding venous anatomy is true EXCEPT

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A. Veins are thin-walled, collapsible, and highly distensible to a diameter several times greater than that in the supine position.

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B. The venous intima is composed of a nonthrombogenic endothelium that produces endothelium-derived relaxing factors such as nitric oxide and prostacyclin.

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C. Venous valves close in response to caudal-to-cephalad blood flow at a velocity of at least 30 cm/s2.

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D. The inferior vena cava (IVC), common iliac veins, portal venous system, and cranial sinuses are valveless.

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Answer: C

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Veins are thin-walled, highly distensible, and collapsible. Their structure specifically supports the primary functions of veins to transport blood toward the heart and serve as a reservoir to prevent intravascular volume overload.

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The venous intima is composed of a nonthrombogenic endothelium with an underlying basement membrane and an elastic lamina. The endothelium produces endothelium-derived relaxing factors such as nitric oxide and prostacyclin, which help maintain a nonthrombogenic surface through inhibition of platelet aggregation and promotion of platelet disaggregation.

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Circumferential rings of elastic tissue and smooth muscle located in the media of the vein allow for changes in vein caliber with minimal changes in venous pressure. The adventitia is most prominent in large veins and consists of collagen, elastic fibers, and fibroblasts. When a vein is maximally distended, its diameter may be several times greater than that in the supine position.

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In the axial veins, unidirectional blood flow is achieved with multiple venous valves. The inferior vena cava (IVC), common iliac veins, portal venous system, and cranial sinuses are valveless. In the axial veins, valves are more numerous distally in the extremities than proximally. Each valve consists of two thin cusps of a fine connective tissue skeleton covered by endothelium. Venous valves close in response to cephalad-to-caudal blood flow at a velocity of at least 30 cm/s2. (See Schwartz 10th ed., p. 915.)

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Chronic venous insufficiency (CVI) is characterized by all of the following EXCEPT

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A. Incompetence of venous valves, venous obstruction

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B. Preserved microcirculatory and cutaneous lymphatic anatomy

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C. Eczema and dermatitis

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D. Lipodermatosclerosis

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Answer: B

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Chronic venous insufficiency (CVI) may lead to characteristic changes in the skin and subcutaneous tissues in the affected limb. CVI results from incompetence of venous valves, venous obstruction, or both. Most CVI involves venous reflux, and severe CVI often reflects a combination of reflux ...

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