Ch.19 - Disorders of the Venoud system

Characteristics of veins

• thin walled, flexible

• return blood to the heart

• work in a low pressure system compared to arteries (why we do IVs on veins)

• composed of three layers

  • tunica intima: interior endothelial cell lining

  • tunica media: smooth muscle

  • tunica adventitia: exterior layer of connective tissue

Two systems of veins

• superficial, small diameter veins

  • skin and subcutaenous tissue

  • drains into deep veins

• deep, large diameter veins

  • empty into inferior and superior vena cava

• perforating veins connect the two systems and run at an angle between superficial and deep veins

Do veins pump blood?

Veins DO NOT pump blood

• they must work against the flow of gravity and rely on skeletal muscle to pump and valves to prevent backflow

• they have large capacity (large stretch), which is why there are susceptible to venous stasis

• hardness of veins is an inheritable quality - familial predisposition for venous insufficiency

How does venous insufficiency affect veins?

Venous insufficiency = leaky veins

• can affect superficial veins: superficial vein distention EX: visible varicose veins

• can affect deep veins: susceptible to increased hydrostatic pressure EX: standing - gravity > flow, which can lead to edema

  • deep vein insufficiency, which can lead to DVT

• obesity and pregnancy can weaken valve leaflets in veins d/t greater blood volume that needs to be moved

Deep Vein Thrombosis

• encompasses both