Chapter 19_1 flashcards
(23 cards)
Veins: Basic Characteristics & Function
Thin-walled, flexible blood vessels that return blood to the heart; operate as a low-pressure system and contain valves to prevent backflow.
Venous Wall Layers
- Tunica intima: Endothelial cell lining. 2. Tunica media: Thin layer of smooth muscle. 3. Tunica adventitia: Exterior layer of connective tissue.
Two Systems of Veins
- Superficial veins: Small diameter, in skin and subcutaneous tissues, drain into deep veins. 2. Deep veins: Large diameter, empty into inferior and superior vena cava. Perforating veins connect the two systems.
Mechanisms of Venous Blood Flow
Veins do not actively pump blood; they rely on the skeletal muscle pump (e.g., gastrocnemius muscle in calf) and one-way valves to move blood against gravity toward the heart.
Vein Capacity & Predisposition to Stasis
Veins have a large capacity (carry ~2/3 of body’s blood volume) and can expand, making them susceptible to stasis (pooling) of blood. Venous hardiness can be an inheritable quality.
Venous Insufficiency: General Cause
Occurs when valves in veins are damaged or incompetent, leading to retrograde (backward) blood flow and venous stasis. Often due to prolonged standing, obesity, or pregnancy.
Superficial Venous Insufficiency: Common Consequence
Leads to varicose veins, where superficial veins become distended and distorted due to high pressure from valvular incompetence.
Deep Venous Insufficiency: Consequences
Can lead to edema in lower extremities (due to increased hydrostatic pressure), poor waste clearance, and increased risk for Deep Vein Thrombosis (DVT).
Venous Thromboembolism (VTE): Definition
A term encompassing both Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE).
Virchow’s Triad: Risk Factors for DVT
Three predisposing factors: 1. Venous stasis (e.g., immobility, sedentary behavior). 2. Vascular damage (e.g., trauma, surgery, especially orthopedic). 3. Hypercoagulability (e.g., cancer, high estrogen levels, smoking, genetic conditions).
Assessment of Venous Disorders: General Approach
Involves looking for signs of Virchow’s triad, unilateral leg symptoms (pain, redness, swelling), but symptoms can be absent or nonspecific. Imaging is often required.
Treatment of Venous Disorders: General Preventive Strategies
Gradient compression stockings, pneumatic compression devices, elevation of extremities, regular movement/ambulation.
Treatment of Venous Disorders: General Pharmacological Approaches
Anticoagulants (e.g., heparin, warfarin, DOACs) and antiplatelet medications are used to prevent or treat clots. Thrombolytic agents (“clot busters”) dissolve existing clots.
Key Term: Deep Venous Thromboembolism (DVT)
Formation of a blood clot (thrombus) in a deep vein, most commonly in the lower extremity.
Key Term: Gradient Compression Stockings
Supportive hosiery providing higher compression at the ankle than proximally up the leg, used to improve venous return.
Key Term: Pulmonary Embolism (PE)
A clot (usually originating as a DVT) that travels through the venous system to the right side of the heart and lodges in the pulmonary arterial circulation, obstructing blood flow to the lungs.
Key Term: Stasis Dermatitis
A circumferential dusky discoloration often noted around the ankle, instep, and lower leg in chronic venous insufficiency, caused by the buildup of hemosiderin (iron-containing pigment from RBC breakdown).
Key Term: Varicose Veins
Abnormally dilated, tortuous superficial veins, usually in the legs, caused by valvular incompetence and high pressure within the superficial veins.
Key Term: Venous Ulcer (Venous Stasis Ulcer)
Skin wounds, often on the lower limbs (especially medial malleolus), caused by trauma or pressure in areas affected by venous insufficiency and poor circulation.
Key Term: Virchow’s Triad
The three primary factors predisposing to DVT: venous stasis, vascular (endothelial) damage, and hypercoagulability.
Key Term: Wells Criteria
A clinical decision rule used to estimate the pretest probability of DVT based on clinical signs and risk factors.
Key Term: D-dimer test
A blood test that measures fibrin clot degradation products; used to help rule out DVT/PE if negative, but not specific for diagnosis if positive.
Key Term: Sclerotherapy
A treatment for varicose veins where a sclerosing substance is injected into the veins to cause fibrosis and eventual reabsorption.
