Where is the femoral nerve located and how is it formed?
The femoral nerve (n. femoralis) is formed by the anterior rami of spinal nerves L₂–L₄ as part of the lumbar plexus (plexus lumbalis). It enters the thigh by passing through the muscular lacuna (lacuna musculorum), which is separated from the vascular lacuna by the iliopectineal arch (arcus iliopectineus). In the femoral triangle, the n. femoralis lies lateral to the femoral vessels (a. et v. femorales), being separated from them by the fascia of the iliopsoas muscle.
What branches does the femoral nerve give off?
Almost immediately after entering the thigh, the femoral nerve divides into multiple branches:
- Deep branches — run to the heads of the quadriceps femoris muscle and to the pectineus muscle (m. pectineus).
- Anterior cutaneous branches (rr. cutanei anteriores) — pierce the fascia lata along the medial margin of the sartorius muscle (m. sartorius) and supply the skin of the anterior surface of the thigh.
- Saphenous nerve (n. saphenus) — the longest branch of the femoral nerve, which accompanies the femoral vessels in the adductor canal, emerges onto the leg, and innervates the skin of the medial surface of the leg and the medial margin of the foot.
What does the femoral nerve innervate?
The nerve is responsible for the motor and sensory innervation of the following structures:
- Muscles: the heads of the quadriceps femoris muscle, the iliopsoas muscle (thigh flexion and medial rotation), the sartorius muscle (m. sartorius), and it also participates in the dual innervation of the pectineus muscle (m. pectineus).
- Skin: the anterior surface of the thigh (rr. cutanei anteriores) and the medial surface of the leg along with the medial margin of the foot (n. saphenus).
The knee-jerk reflex is also associated with the function of the femoral nerve (at the L₂–L₄ segments).
What structures is the femoral nerve associated with in the subinguinal region?
In the region of the lacunae below the inguinal ligament, n. femoralis passes lateral to the vascular bundle. In the muscular lacuna (lacuna musculorum), it is accompanied by the iliopsoas muscle (m. iliopsoas) and the lateral femoral cutaneous nerve (n. cutaneus femoris lateralis). Medially, in the vascular lacuna (lacuna vasorum), lie the femoral artery and vein, as well as the femoral branch of the genitofemoral nerve (r. femoralis n. genitofemoralis).
Class and exam questions
From which segments is the femoral nerve formed?
The femoral nerve (n. femoralis) is formed from the anterior rami of spinal nerves L₂–L₄ as part of the lumbar plexus.
Through which structure does the femoral nerve enter the thigh?
The femoral nerve enters the thigh through the muscular lacuna (lacuna musculorum).
What is the spatial relationship between the femoral nerve and the vessels in the femoral triangle?
In the femoral triangle, the femoral nerve is located lateral to the femoral artery and vein.
Which branch of the femoral nerve accompanies the vessels down to the leg?
The vessels are accompanied by the longest branch of the femoral nerve — the saphenous nerve (n. saphenus).
What else to study on this topic
- Lumbar plexus (plexus lumbalis)
- Muscular lacuna (lacuna musculorum)
- Femoral triangle
- Adductor canal (canalis adductorius)
- Saphenous nerve (n. saphenus)
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