Superficial layers and landmarks
A dense network of blood vessels and nerves is located in the subcutaneous tissue of the anterosuperior region of the thigh. Among the arteries and veins are:
- Superficial epigastric vessels (vasa epigastrica superficialia).
- Superficial circumflex iliac vessels (vasa circumflexa ilium superficialia).
- External pudendal vessels (vasa pudenda externa).
- Great saphenous vein of the leg (v. saphena magna).
Skin innervation in this area is provided by the anterior cutaneous nerves of the thigh (nn. cutanei femoris anteriores), lateral cutaneous nerve of the thigh (n. cutaneus femoris lateralis), and ilioinguinal nerve (n. ilioinguinalis).
The most important fascial structure of the superficial layer is the saphenous opening (hiatus saphenus), bounded by the sickle-shaped margin (margo falciformis). It acts as the superficial ring of the femoral canal through which superficial arteries emerge. The trunk of the great saphenous vein serves as the key anatomical landmark for locating this opening.
Inguinal lymph nodes and lymphatic drainage pathways
Superficial inguinal lymph nodes lie within the subcutaneous tissue of the femoral triangle. They are divided into three groups depending on their location and the area of lymphatic drainage:
- Inferior nodes (nodi inguinales superficiales inferiores) lie along the projection of the femoral artery. They collect lymph from the skin of the lower limb.
- Superomedial and superolateral nodes (nodi inguinales superficiales superomediales et superolaterales) extend along the inguinal ligament. They receive lymph from the anterior abdominal wall below the umbilicus, external genitalia, skin of the anal triangle, lumbar and gluteal regions, as well as from the uterine fundus (along the course of the round ligament vessels).
Lymph drainage pathway: From the superficial nodes, lymph flows to the deep inguinal nodes, which are hidden beneath the deep fascia (fascia lata) along the femoral artery. Further, the lymph flow proceeds into the pelvic cavity—toward the external iliac nodes (nodi lymphoidei iliaci externi) surrounding the artery of the same name.
Fascia lata and intermuscular septa
The fascia lata of the thigh (fascia lata) is a dense connective tissue sheath enclosing all the thigh muscles. Superiorly, it fuses firmly with the inguinal ligament and posteriorly transitions into the gluteal fascia. On the lateral surface of the thigh, the fascia forms a strong thickening, the iliotibial tract (tractus iliotibialis).
The fascia lata forms isolated sheaths for several superficial muscles:
- Tensor fasciae latae (m. tensor fasciae latae).
- Sartorius muscle (m. sartorius).
- Adductor longus muscle (m. adductor longus).
- Gracilis muscle (m. gracilis).
Three intermuscular septa (septa intermuscularia)—lateral, medial, and posterior—extend from the fascia deep toward the linea aspera of the femur (linea aspera). These septa divide the subfascial space into three compartments:
- Anterior compartment (includes the femoral triangle)—contains the knee extensor muscles.
- Posterior compartment—contains the flexor muscles.
- Medial compartment—contains the adductor muscles.
Floor of the triangle and deep topography
The femoral triangle itself is located within the anterior fascial compartment. Near the medial margin of the sartorius muscle, the fascia lata splits into two layers (superficial and deep).
Beneath the deep layer lies the floor of the femoral triangle, the iliopectineal fossa (fossa iliopectinea). The floor is formed by two muscles passing toward the lesser trochanter of the femur:
- Laterally—iliopsoas muscle (m. iliopsoas).
- Medially—pectineus muscle (m. pectineus).
The short adductor and external obturator muscles also lie in the deep layer of the floor.
The major blood vessels (a. et v. femoralis) enter the femoral triangle from the vascular lacuna (the subinguinal space divided by the iliopectineal arch). Their entry point is medial to the midpoint of the inguinal ligament. The vessels are surrounded by a dense fascial sheath, and medial to the femoral vein lies the femoral ring (anulus femoralis), the deep opening of the femoral canal.
Briefly: answers to topical questions
Which nerves innervate the skin in the region of the femoral triangle?
The skin in the region of the femoral triangle is innervated by the following nerves:
- Lateral cutaneous nerve of the thigh (n. cutaneus femoris lateralis)—runs in the subcutaneous tissue inferior to the anterior superior iliac spine.
- Ilioinguinal nerve (n. ilioinguinalis).
- Anterior cutaneous nerves of the thigh (nn. cutanei femoris anteriores).
- Femoral branch of the genitofemoral nerve (r. femoralis n. genitofemoralis)—branches out beneath the medial part of the inguinal ligament and innervates the skin of this region.
- Cutaneous branch of the obturator nerve (r. cutaneus n. obturatorii)—runs along the medial surface of the thigh down to the level of the patella.
What bounds the saphenous opening (hiatus saphenus)?
The saphenous opening (hiatus saphenus) is bounded by structures of the fascia lata of the thigh. The following elements participate in its formation:
- Sickle-shaped margin (m. falciformis)—bounds the opening laterally (on the outer side).
- Superior horn (cornu superius) — the upper part of the falciform margin.
- Inferior horn (cornu inferius)—the lower part over which the great saphenous vein of the leg (v. saphena magna) arches.
The opening itself is covered by the cribriform fascia (fascia cribrosa).
What anatomical structures form the boundaries of the femoral triangle?
The boundaries of the femoral triangle (trigonum femorale) are formed by the muscles of the thigh and a pelvic ligament. These include:
- Base—inguinal ligament (lig. inguinale).
- Lateral boundary—sartorius muscle (m. sartorius).
- Medial boundary—adductor longus muscle (m. adductor longus).
- Apex—the point of intersection of the sartorius and adductor longus muscles.
What passes through the muscular and vascular lacunae beneath the inguinal ligament?
Muscles, vessels, and nerves emerge onto the anterior surface of the thigh through the spaces beneath the inguinal ligament.
- Muscular lacuna (lacuna musculorum): contains the iliopsoas muscle (m. iliopsoas) and femoral nerve (n. femoralis).
- Vascular lacuna (lacuna vasorum): transmits the femoral artery (a. femoralis), femoral vein (v. femoralis), femoral branch of the genitofemoral nerve (ramus femoralis n. genitofemoralis), and lymphatic vessels.
What bounds the femoral ring (anulus femoralis)?
The femoral ring (anulus femoralis) is bounded by ligaments and a large blood vessel. Its boundaries include four margins:
- Anteriorly — inguinal ligament (lig. inguinale).
- Posteriorly — the pectineal ligament (lig. pectineale), located on the pecten of the pubic bone.
- Medially — the lacunar ligament (lig. lacunare), situated in the angle between the inguinal ligament and the pecten of the pubic bone.
- Laterally — femoral vein (v. femoralis).
Along which line is the femoral artery projected within the femoral triangle?
The femoral artery (a. femoralis) is projected along Keen's line. This line is drawn from the midpoint of the inguinal ligament to the medial epicondyle of the femur. To determine the projection, the limb should be slightly flexed at the knee joint and abducted outwards. Within the femoral triangle, the femoral vessels lie along the bissector of the triangle — from the base to the apex.
Class and exam questions
Where is the femoral ring located and what is it?
The femoral ring (anulus femoralis) is located medial to the femoral vein within the subinguinal space. It serves as the deep opening of the femoral canal.
Which muscles form the floor of the femoral triangle?
The floor of the triangle (iliopectineal fossa) is formed by the iliopsoas muscle (lying laterally) and the pectineus muscle (located medially).
In which direction does the neurovascular bundle run within the femoral triangle?
The femoral vessels are projected strictly along the bissector of the triangle, running from its base (inguinal ligament) to its apex.
Into how many fascial compartments is the thigh divided?
Intermuscular septa divide the thigh into three compartments: anterior (extensors), posterior (flexors), and medial (adductors).
What else to study on this topic
- Anatomy of the femoral canal: walls and rings
- Topography of the muscular and vascular lacunae (lacuna musculorum et vasorum)
- Topography of the neurovascular bundles in a cross-section of the upper third of the thigh
- Syntopy of the femoral artery, vein, and nerve
- Deep artery of the thigh and its branches
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