Topographic anatomy of the femoral artery and vein
The femoral artery (a. femoralis) is the direct continuation of the external iliac artery (a. iliaca externa). Its diameter ranges from 8 to 12 mm. At the level of the saphenous opening (hiatus saphenus), the artery is anteriorly covered by the falciform margin (margo falciformis). In this region, the vessel gives off three superficial branches:
- Superficial epigastric artery (a. epigastrica superficialis).
- Superficial circumflex iliac artery (a. circumflexa ilium superficialis).
- Superficial and deep external pudendal arteries (aa. pudendae externae superficialis et profundus).
In the upper third of the thigh, the femoral vein (v. femoralis) lies medial to the artery and is covered by the cribriform fascia (fascia cribrosa). It receives the great saphenous vein (v. saphena magna) as well as veins accompanying the superficial arteries. An important topographic feature is the course of the venous trunk: as it descends, the vein gradually shifts to the posterior surface of the artery. Upon reaching the apex of the femoral triangle, the vein is completely hidden behind the arterial trunk.
Deep artery of the thigh and its branches
The deep artery of the thigh (a. profunda femoris) is its largest branch and gradually diverges posteriorly from the main femoral artery along its course. The distance between these two vessels increases from top to bottom:
- At the apex of the femoral triangle: the distance is only 0.5–1.0 cm.
- Lower down (at the level of the tendon of the adductor longus muscle — m. adductor longus): the vessels diverge by 3.0–3.5 cm.
At the very beginning of its course, the deep artery of the thigh (or in some cases, directly from the femoral artery itself) gives off two massive branches supplying the muscles and joint: the medial femoral circumflex artery (a. circumflexa femoris medialis) and the lateral femoral circumflex artery (a. circumflexa femoris lateralis).
Femoral nerve
The femoral nerve (n. femoralis) enters the thigh from the muscular lacuna (lacuna musculorum). Within the boundaries of the femoral triangle, it is located lateral to the main vessels. It is important to note that the vessels and nerve are reliably separated by the fascia of the iliopsoas muscle.
Almost immediately after its exit, the nerve divides into multiple branches:
- Deep branches run toward the muscular structures, innervating the heads of the quadriceps femoris and the pectineus muscle.
- Superficial branches (rr. cutanei anteriores) pierce the fascia lata, passing through the fascial sheath of the sartorius muscle, and head toward the skin.
Among all the numerous branches, the femoral vessels are accompanied along their further course exclusively by a single, longest branch — the saphenous nerve (n. saphenus).
Communications of the femoral triangle fascial spaces
The adipose tissue of the femoral triangle is not isolated. It has anatomical communications with adjacent regions, which is of critical importance in the spread of hematomas or purulent processes:
- With the subperitoneal floor of the pelvis: communication occurs through the vascular lacuna directly along the course of the femoral vessels.
- With the subcutaneous tissue: through natural openings in the cribriform fascia (which fills the hiatus saphenus) along the course of the superficial branches of the femoral vessels.
- With the gluteal region: the pathway of spread runs along the lateral femoral circumflex artery.
- With the adductor compartment: along the course of the medial femoral circumflex artery.
- With the adductor canal: communication is established along the course of the main femoral vessels.
- With the posterior fascial compartment of the thigh: the pathway runs along the perforating branches of the deep artery of the thigh (aa. perforantes).
Briefly: answers to topical questions
Which veins are tributaries of the femoral vein?
The tributaries of the femoral vein are the great saphenous trunk and smaller vessels accompanying the superficial arteries.
- Great saphenous vein (v. saphena magna) — drains into the femoral vein in the area of the saphenous opening, piercing the superficial layer of the fascia lata of the thigh.
- Corresponding veins — accompany the superficial arteries of the thigh.
Which anatomical structures form the boundaries of the femoral triangle?
The boundaries of the femoral triangle are formed by two thigh muscles and one ligament.
- Inguinal ligament (lig. inguinale) — forms the base of the triangle.
- Sartorius muscle (m. sartorius) — serves as the lateral boundary.
- Adductor longus muscle (m. adductor longus) — acts as the medial boundary.
The apex of the triangle is formed at the intersection of the sartorius and adductor longus muscles.
What passes through the vascular lacuna (lacuna vasorum)?
The vascular lacuna transmits major femoral vessels, a nerve, and lymphatic structures.
- Femoral artery (a. femoralis) — located laterally in the lacuna.
- Femoral vein (v. femoralis) — lies medial to the artery.
- Femoral branch of the genitofemoral nerve (r. femoralis n. genitofemoralis) — accompanies the vessels.
- Loose adipose tissue and the lymph node of Pirogov–Rosenmüller — pass through the femoral ring, located in the most medial part of the vascular lacuna.
How is the projection line of the femoral artery (Keen's line) constructed?
The projection line of the femoral artery (Keen's line) is constructed between two anatomical landmarks with a specific position of the lower limb.
- Starting point — midpoint of the inguinal ligament.
- End point — medial epicondyle of the femur.
To correctly construct the projection, the limb must be placed in a special position: the leg should be slightly flexed at the knee joint and abducted outward.
The "VAN" rule: moving from the midline (medial) outwards (lateral) in the upper thigh, the structures are arranged in the order Vein — Artery — Nerve.
Class and exam questions
Where is the femoral vein located in relation to the artery?
In the proximal thigh, the vein lies medially. Descending inferiorly, it gradually shifts to the posterior surface of the artery, hiding behind it at the apex of the femoral triangle.
Through which anatomical formation does the femoral nerve enter the thigh?
The femoral nerve leaves the pelvic cavity and enters the thigh through the muscular lacuna (lacuna musculorum).
Which branch of the femoral nerve accompanies the major vessels?
Of all the branches of the femoral nerve, the vessels are accompanied by only a single, longest branch — the saphenous nerve.
Where does the great saphenous vein (v. saphena magna) drain?
The great saphenous vein empties into the femoral vein in the region of the saphenous opening (hiatus saphenus), lying beneath the cribriform fascia.
What else to study on this topic
- Anatomy of the muscular and vascular lacunae
- Structure and boundaries of the femoral triangle
- Topography of the saphenous opening (hiatus saphenus) and cribriform fascia
- Innervation of the skin of the anterior surface of the thigh
- Adductor canal and its contents
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