The sartorius muscle (/sɑːrˈtɔːriəs/) is the longest muscle in the human body. It is a long, thin, superficial muscle that runs down the length of the thigh in the anterior compartment.Muscles of the iliac and anterior femoral regions.Cross-section through the middle of the thigh.The left femoral triangle.Front and medial aspect of right thigh.Sartorius muscleSartorius muscleSartorius muscleSartorius muscleSartorius muscleSartorius muscleMuscles of thigh. Cross section. The sartorius muscle (/sɑːrˈtɔːriəs/) is the longest muscle in the human body. It is a long, thin, superficial muscle that runs down the length of the thigh in the anterior compartment.