Topographic anatomy of the muscular lacuna
The space located immediately inferior to the inguinal ligament is divided into two parts. The outer (lateral) two-thirds of this extensive interval form the muscular lacuna (lacuna musculorum).
The architectonics of the muscular lacuna walls include three main boundaries:
- Anteriorly, the space is covered by the inguinal ligament (lig. inguinale).
- Posteriorly, the bed is formed by the prominent pecten of the pubic bone.
- Medially, the boundary is formed by the iliopectineal arch (arcus iliopectineus).
The main content of this lacuna is the massive iliopsoas muscle (m. iliopsoas), which emerges onto the anterior surface of the thigh. Accompanying it is the femoral nerve (n. femoralis), a major branch of the lumbar plexus.
Structure and contents of the vascular lacuna
Considerably more medially lies the vascular lacuna (lacuna vasorum). It is separated from the muscular part by the tendinous iliopectineal arch, which acts as its lateral wall.
The remaining boundaries of the vascular lacuna are formed by the following structures:
- Anteriorly, the wall remains the inguinal ligament.
- Posteriorly, the pecten of the pubic bone is also located.
- Medially, the space is bounded by the lacunar ligament, or Gimbernat's ligament (lig. lacunare).
Passing through this canal are the major trunks of the thigh — the femoral artery and vein (a. et v. femoralis). Their mutual arrangement is strictly constant: the vein always occupies the medial position, while the artery lies laterally. Adjacent to the blood vessels is the femoral branch of the genitofemoral nerve.
Fascia lata and cribriform fascia
The fascial structures of the thigh are represented by the superficial and deep layers of the fascia lata. The superficial layer is heterogeneous. In the lateral third, projected over the sartorius muscle (m. sartorius), it is dense. In the medial part, the structure is loose and designated as the cribriform fascia (fascia cribrosa).
Approximately 1–2 centimeters inferior to the medial third of the inguinal ligament, a natural opening forms within the cribriform fascia — the saphenous opening (hiatus saphenus). Through it, the great saphenous vein of the lower limb (v. saphena magna) penetrates into the depth. The margins of the saphenous opening have a distinct configuration:
- On the lateral side, it is bounded by the falciform margin (margo falciformis).
- Superiorly and inferiorly, the margin transitions into the superior and inferior horns (cornu superius et cornu inferius). The inferior horn is easily identified visually, as the trunk of the vein arches over it.
The deep layer (fascia iliopectinea) runs posterior to the femoral vessels, fusing with the fasciae of the iliopsoas and pectineus muscles, and connects with the superficial leaf in the region of the adductor longus muscle.
Clinical and topographic significance
The anatomy of the vascular lacuna is critically important for clinical practice. In emergency situations involving massive arterial hemorrhage, it is precisely at the projection of the vascular lacuna that the femoral artery can be firmly compressed against the underlying pubic bone. This allows for temporary cessation of blood loss in case of major vessel injury.
Furthermore, the saphenous opening (hiatus saphenus) is of great significance: it serves as the superficial (subcutaneous) ring of the femoral canal. The deep ring, in turn, is the femoral ring (anulus femoralis).
Topography of the thigh musculature
Structures exiting through the lacunae enter the anterior region of the thigh, where they are surrounded by a robust muscular framework. A key bony landmark is the anterior superior iliac spine (spina iliaca anterior superior).
In this zone, the rectus femoris muscle (m. rectus femoris), vastus medialis muscle (m. vastus medialis), and tensor fasciae latae muscle (m. tensor fasciae latae) are localized. The medial group is represented by the pectineus muscle (m. pectineus), adductor magnus and adductor longus muscles (m. adductor magnus, m. adductor longus), as well as the gracilis muscle (m. gracilis). The saphenous nerve and the descending genicular artery are also topographically defined in this area.
Briefly: answers to topical questions
Which anatomical structures form the walls of the muscular lacuna?
The walls of the muscular lacuna (lacuna musculorum) are formed by the inguinal ligament, the ilium, and the iliopectineal arch.
- Anteriorly — inguinal ligament (lig. inguinale).
- Posteriorly — iliac crest or ilium.
- Medially — iliopectineal arch (arcus iliopectineus).
- Laterally — free lateral margin of the ilium.
What passes through the muscular lacuna?
Muscles and nerves emerge onto the anterior surface of the thigh through the muscular lacuna (lacuna musculorum).
- Iliopsoas muscle (m. iliopsoas) — formed by the confluence of the iliacus and psoas major muscles.
- Femoral nerve (n. femoralis) — a branch of the lumbar plexus, located lateral to the vessels.
- Lateral femoral cutaneous nerve (n. cutaneus femoris lateralis).
What forms the walls of the vascular lacuna?
The walls of the vascular lacuna (lacuna vasorum), located medial to the muscular lacuna, are formed by the following anatomical structures:
- Anteriorly — inguinal ligament (lig. inguinale).
- Posteriorly — pecten of the pubic bone (pecten ossis pubis).
- Laterally — iliopectineal arch (arcus iliopectineus).
- Medially — lacunar ligament, or Gimbernat's ligament (lig. lacunare).
What anatomical structures pass through the vascular lacuna?
Blood and lymphatic vessels, as well as a nerve, pass through the vascular lacuna (lacuna vasorum).
- Femoral artery (a. femoralis) — located laterally.
- Femoral vein (v. femoralis) — located medially relative to the artery.
- Femoral branch of the genitofemoral nerve (ramus femoralis n. genitofemoralis).
- Lymphatic vessels and lymph nodes.
In the most medial part of the lacuna lies the femoral ring (anulus femoralis).
What structures form the walls of the deep femoral ring (anulus femoralis)?
The walls of the deep femoral ring (anulus femoralis) are formed by ligaments and a blood vessel.
- Anteriorly — inguinal ligament (lig. inguinale).
- Posteriorly — pectineal ligament, or Cooper's ligament (lig. pectineale), located on the pecten of the pubic bone.
- Medially — lacunar ligament, or Gimbernat's ligament (lig. lacunare).
- Laterally — femoral vein (v. femoralis).
Where is the Pirogov-Rosenmüller lymph node located topographically?
The Pirogov-Rosenmüller lymph node is topographically located in the most medial part of the vascular lacuna (lacuna vasorum).
It lies directly beneath the inguinal ligament (lig. inguinale), medial to the femoral vein (v. femoralis). This large deep inguinal lymph node is the contents of the femoral ring (anulus femoralis), which is covered from the abdominal cavity side by the transversalis fascia.
The mutual arrangement of blood vessels in the vascular lacuna is easy to remember by the rule: Vein is In-between (medially), Artery is Out-side (laterally).
Class and exam questions
What separates the muscular lacuna from the vascular lacuna?
The role of the dense septum between the muscular and vascular lacunae is played by the iliopectineal arch (arcus iliopectineus). It serves as the medial wall for the muscular lacuna and the lateral wall for the vascular lacuna.
Which nerves pass beneath the inguinal ligament in the region of the lacunae?
The femoral nerve (a branch of the lumbar plexus) exits through the muscular lacuna, while the femoral branch of the genitofemoral nerve passes through the vascular lacuna.
Where is the superficial opening of the femoral canal located?
The superficial, or subcutaneous, opening of the femoral canal is the saphenous hiatus (hiatus saphenus). It is a defect in the cribriform fascia located 1–2 cm below the inner third of the inguinal ligament.
Over which structure does the greater saphenous vein of the lower limb arch?
The great saphenous vein of the lower limb (v. saphena magna) arches over the inferior horn (cornu inferius) of the saphenous hiatus, diving deep.
What else to study on this topic
- Detailed topography and borders of the femoral triangle.
- Anatomy of the femoral ring (anulus femoralis) and pathways of femoral hernia emergence.
- Topographical anatomy of the greater saphenous vein of the lower limb and its tributaries.
- Branches of the femoral nerve on the anterior surface of the thigh.
- Fascial compartments of the thigh and the course of the deep lamina of the fascia lata.
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