The structure indicated is the adductor magnus muscle of the thigh.
The adductor magnus muscle is one of six muscles in the medial compartment of the thigh. The medial compartments consists of the following muscles:
- Adductor longus
- Adductor brevis
- Adductor magnus
- Obturator externus
The adductor magnus muscle is the largest muscle in the medial compartment. It lies deep to the adductor brevis and the adductor longus. It has two parts to it:
- Adductor part
- Hamstring part
The adductor part originates on the ischiopubic ramus, and as the name suggests, contraction causes adduction, as well as medial rotation of the thigh.
The hamstring part originates on the ischial tuberosity and contraction results in extension of the hip.
Distally, there is a hole in the adductor magnus muscle known as the adductor hiatus (not shown in image). This allows the femoral artery and veins to pass from the anterior compartment of the thigh into the posterior compartment.
Origin: adductor part – anteroinferior pubic ramus; hamstring part – ischial tuberosity
Insertion: adductor part – linea aspera, hamstring part – adductor tubercle
Action: adduction of hip (adductor part), extension of hip (hamstring part)
Innervation: adductor part - obturator nerve, hamstring part – tibial nerve (from sciatic nerve)
Learn all about the anatomy of the thigh muscles in this tutorial.