The femoral vein is a large, deep vein located in the thigh, running alongside the femoral artery. It begins at the lower part of the thigh, formed by the continuation of the popliteal vein after it passes through the adductor canal. The femoral vein ascends through the thigh, traveling medially and posteriorly to the femoral artery, and runs through the femoral triangle. As it reaches the inguinal ligament, it continues upward to become the external iliac vein. The femoral vein also receives blood from several tributaries, including the great saphenous vein, deep femoral vein, and other smaller veins from the thigh and surrounding tissues.
Structure and Anatomy
Location and Structure
The femoral vein is a large, deep vein that runs through the thigh. It begins as the continuation of the popliteal vein after it emerges from the adductor hiatus in the lower thigh. The vein ascends medially through the thigh, running alongside the femoral artery, which lies lateral to it. The femoral vein lies deeper than the artery within the femoral triangle, a region bound by the sartorius, adductor longus, and inguinal ligament. As it moves upward, the femoral vein travels toward the inguinal ligament, where it transitions into the external iliac vein.
Origin and Course
The femoral vein originates from the popliteal vein in the lower thigh, following the path of the femoral artery. It runs in close proximity to the artery throughout its course, passing through the adductor canal and into the femoral triangle. The femoral vein lies posterior to the artery initially, but as it ascends, it moves medially in relation to the artery, eventually lying directly medial by the time it reaches the inguinal ligament.
At the upper end of the thigh, the femoral vein passes beneath the inguinal ligament, marking its transition into the external iliac vein. This anatomical change is an important landmark, as the external iliac vein becomes one of the major veins of the pelvic region, continuing its course toward the inferior vena cava.
Tributaries
Throughout its course, the femoral vein receives blood from several significant tributaries:
- Great saphenous vein: The largest superficial vein of the leg, which drains into the femoral vein in the femoral triangle near the saphenofemoral junction.
- Deep femoral vein (profunda femoris vein): A large tributary that drains the deep structures of the thigh, including the muscles and bones, and joins the femoral vein midway up the thigh.
- Medial and lateral circumflex femoral veins: These veins drain the hip and thigh region, specifically around the femoral head and surrounding muscles.
- Muscular veins: Smaller tributaries that drain blood from the thigh’s muscles, particularly the quadriceps, adductors, and hamstrings.
Relationship with Surrounding Structures
The femoral vein is located within the femoral sheath, which also contains the femoral artery and the femoral canal. It lies medial to the femoral artery in the upper part of the thigh and deep within the fascial layers of the thigh muscles. The femoral vein is closely related to several important anatomical landmarks:
- Femoral triangle: The femoral vein is located within the femoral triangle, which is formed by the sartorius, adductor longus, and inguinal ligament. This triangular space is crucial for surgical access and venous puncture procedures.
- Femoral sheath: A fascial covering that encloses the femoral artery and vein, protecting them as they pass through the femoral triangle.
- Inguinal ligament: The femoral vein passes under the inguinal ligament, where it transitions into the external iliac vein. This area is an important surgical landmark and the site for venous access.
Valves
The femoral vein contains several one-way valves that are crucial for preventing the backflow of blood. These valves help direct venous blood flow upward, ensuring that it moves toward the heart and does not pool in the lower limbs. The number of valves in the femoral vein can vary, but they are typically located at intervals along the vein’s length, particularly near its junction with the great saphenous vein.
Transition to External Iliac Vein
As the femoral vein ascends through the thigh and reaches the inguinal ligament, it continues as the external iliac vein. This transition marks the point where venous blood from the lower limb is directed into the venous system of the pelvis. The external iliac vein eventually drains into the common iliac vein, which then leads to the inferior vena cava, completing the return of deoxygenated blood to the heart.
Function
Venous Drainage of the Lower Limb
The femoral vein is the main vessel responsible for the drainage of deoxygenated blood from the lower limb, particularly from the thigh, knee, and portions of the lower leg. It collects blood from both the superficial and deep venous systems of the leg and channels it back toward the heart. This process begins at the lower thigh, where the femoral vein is formed by the popliteal vein, and continues upward through the thigh, carrying blood from the entire lower extremity.
Connection with the Superficial Venous System
One of the key roles of the femoral vein is to serve as the point where the superficial venous system of the leg connects to the deep venous system. The most important of these superficial veins is the great saphenous vein, which drains blood from the superficial tissues of the foot, ankle, and lower leg. The great saphenous vein joins the femoral vein in the femoral triangle, forming the saphenofemoral junction. This connection allows for the efficient transfer of blood from the superficial veins to the deep venous system, facilitating proper circulation and venous return.
Deep Venous Drainage of the Thigh
The femoral vein also drains blood from the deep structures of the thigh, including muscles, bones, and connective tissues. Blood from the deep femoral vein (profunda femoris vein) and its tributaries, such as the medial and lateral circumflex femoral veins, enters the femoral vein. These veins collect blood from the deep thigh muscles, particularly the quadriceps and adductor muscles, and ensure proper venous return from the thigh.
Role in Venous Return to the Heart
The femoral vein plays a crucial role in the overall process of venous return, where deoxygenated blood from the lower extremities is returned to the heart for oxygenation. As part of the deep venous system, the femoral vein transports blood upward through the thigh, overcoming the effects of gravity. The femoral vein uses the surrounding muscles’ contractions during movement (such as walking or running) to propel blood upward in a process known as the muscle pump. This process helps maintain proper circulation and prevents blood from pooling in the lower limbs.
One-Way Valves for Preventing Reflux
The femoral vein contains one-way valves that are essential for maintaining the correct flow of blood. These valves prevent the backflow of blood (also called venous reflux), especially when the body is in an upright position. Blood flows upward toward the heart due to the pressure generated by muscle contractions, and the valves close to prevent blood from flowing backward. This function is crucial in ensuring efficient venous return and avoiding conditions like venous insufficiency, which can cause swelling and discomfort.
Integration with the Pelvic Venous System
As the femoral vein ascends through the thigh, it passes under the inguinal ligament and becomes the external iliac vein, which continues into the pelvis. This transition is significant because the external iliac vein ultimately drains into the common iliac vein, which then leads to the inferior vena cava. The femoral vein is, therefore, a critical part of the pathway by which venous blood is transported from the lower extremities to the heart. By connecting the veins of the lower limb to the larger pelvic and abdominal venous systems, the femoral vein ensures the continuity of venous return.
Role in Removal of Metabolic Waste
In addition to transporting deoxygenated blood, the femoral vein plays an important role in removing metabolic waste products such as carbon dioxide, lactate, and other byproducts of cellular activity from the lower limb muscles. As blood flows through the femoral vein, these waste products are carried toward the heart and lungs for elimination from the body. This function is vital for maintaining the health of the tissues in the lower extremities, especially during and after physical activity.
Contribution to Thermoregulation
The femoral vein also contributes to thermoregulation by transporting blood from the lower limbs, where heat is generated during physical activity. As the blood flows through the vein, heat is carried from the extremities to the body’s core, helping to regulate body temperature. This process is particularly important during strenuous activities or exposure to varying environmental conditions, allowing the body to dissipate or retain heat as needed to maintain homeostasis.
Clinical Significance
The femoral vein is clinically significant due to its role in various vascular conditions, particularly deep vein thrombosis (DVT). DVT occurs when a blood clot forms in the femoral vein, often due to prolonged immobility, surgery, or trauma, leading to swelling, pain, and potential complications such as pulmonary embolism if the clot travels to the lungs. The femoral vein is also an important access point for procedures like central venous catheterization, where it is used for intravenous therapies or monitoring. Additionally, the femoral vein can be involved in venous insufficiency, where defective valves lead to poor blood return, resulting in leg swelling and varicose veins. Duplex ultrasound is commonly used to assess the femoral vein for blockages, clots, or valve dysfunction.
