Final answer:
The biceps femoris originates from the ischial tuberosity for the long head and the linea aspera for the short head. It inserts into the head of the fibula and the lateral side of the tibia. Its primary action is to flex the lower leg and extend the thigh.
Step-by-step explanation:
Origination and Insertion of the Biceps Femoris
The biceps femoris is one of the muscles of the posterior thigh that are crucial for movement. This muscle originates from two heads: the long head originates on the ischial tuberosity of the pelvic girdle, while the short head originates on the linea aspera on the posterior shaft of the femur. As for insertion, the biceps femoris inserts into the head of the fibula and the lateral side of the tibia.
Action of the Biceps Femoris
The biceps femoris has multiple actions, primarily involving the leg and the thigh. It primarily acts to flex the lower leg at the knee joint but also aids in extending the thigh at the hip joint. Additionally, when the leg is in a fixed position, it can aid in extending the thigh backward, and it also contributes to the lateral rotation of the leg.