30/11/2022
🔈 VEINS, MUSCULOVENOUS PUMP & VARICOSE VEINS
Although most veins of the trunk occur as large single vessels, veins in the limbs occur as two or more smaller vessels that accompany an artery in a common vascular sheath.
Musculovenous pump. Muscular contractions in the limbs function with the venous valves to move blood toward the heart. The outward expansion of the bellies of contracting muscles is limited by deep fascia and becomes a compressive force, propelling the blood against gravity.
When the walls of veins lose their elasticity, they become weak. A weakened vein dilates under the pressure of supporting a column of blood against gravity. This results in varicose veins - abnormally swollen, twisted veins - most often seen in the legs. Varicose veins have a caliber greater than normal, and their valve cusps do not meet or have been destroyed by inflammation. Varicose veins have incompetent valves; thus, the column of blood ascending toward the heart is unbroken, placing increased pressure on the weakened walls, further exacerbating the varicosity problem. Varicose veins also occur in the presence of degenerated deep fascia. Incompetent fascia is incapable of containing the expansion of contracting muscles; thus, the (musculofascial) musculovenous pump is ineffective.
