Unit
- Superficial veins: The great and small saphenous veins run just beneath the skin, collecting blood from the dermis and subcutaneous tissues. They connect to the deep system via perforating veins that pass through the muscle fascia.
- Deep veins: Located within the muscle compartments, these include the anterior and posterior tibial, peroneal, popliteal, and femoral veins. They carry the majority of venous return from the lower extremities.
- Perforating veins: These short veins penetrate the deep fascia to connect superficial and deep systems. Incompetent perforators are a common cause of venous reflux and ulcer formation.
- Venous valves: Bicuspid leaflets within the vein lumen prevent retrograde flow. They are most numerous in the distal leg and are critical for maintaining unidirectional blood flow toward the heart.
- Venous wall layers: The tunica intima (endothelium and basement membrane), tunica media (smooth muscle and elastic fibers), and tunica adventitia (connective tissue) together allow distension and recoil to accommodate volume changes.
- Calf muscle pump: Contraction of the gastrocnemius and soleus muscles compresses deep veins, propelling blood upward. During relaxation, valves close to prevent backflow, creating a pressure gradient that empties the superficial system.
- Venous pressure dynamics: Standing upright, pressure in the foot veins can reach 80-90 mm Hg. Walking reduces this to 20-30 mm Hg via the muscle pump; failure of this mechanism leads to ambulatory venous hypertension.
- Cutaneous microcirculation: The skin receives blood from arterioles that drain into capillary beds and then into venules. Chronic high venous pressure causes microvascular changes, including fibrin cuff formation and leukocyte trapping.
- Lymphatic interaction: The lymphatic system complements venous drainage by removing interstitial fluid and macromolecules. In chronic venous insufficiency, lymphatic overload contributes to edema and tissue damage.
- Age-related changes: With aging, vein walls lose elasticity, valves become less competent, and the calf muscle pump weakens, increasing the risk of venous reflux and ulcer development in older adults.
- Endothelial dysfunction: Sustained venous hypertension damages the endothelium, reducing nitric oxide production and promoting inflammation. This leads to increased permeability, adhesion molecule expression, and eventual microvascular thrombosis that impairs tissue oxygenation.
- Fibrin cuff theory: In chronic venous insufficiency, leakage of fibrinogen from capillaries forms pericapillary fibrin cuffs. These cuffs impede oxygen diffusion and trap growth factors, contributing to poor wound healing and the characteristic lipodermatosclerosis seen in affected limbs.
- White blood cell trapping: Elevated venous pressure slows capillary flow, causing leukocytes to adhere and become trapped in the microcirculation. Activated neutrophils release proteolytic enzymes and free radicals, leading to tissue damage, inflammation, and eventual ulceration in the gaiter area.
Scope of Practice
Role: Wound Care Coordinator (Non-Physician)
Within scope:
- Teaching patients about basic venous anatomy to explain ulcer origins and treatment rationale.
- Assessing lower extremity for visible edema, skin changes, and varicosities.
- Documenting venous doppler findings reported by vascular lab for care planning.
Outside scope:
- Performing venous duplex ultrasound or interpreting imaging independently.
- Diagnosing venous reflux or deep vein thrombosis without provider order.
- Prescribing compression devices or adjusting treatment based on anatomy findings.
Quick Revision
- The lower limb venous system comprises superficial, deep, and perforating veins with one-way valves.
- The calf muscle pump reduces venous pressure during walking; its failure causes venous hypertension.
- Wound care coordinators educate patients on anatomy but do not interpret vascular imaging.