Anatomy Quiz #1 – Lower Extremities – Quadriceps

Four is the usual answer. A fifth muscle, the Articularis genu, lies directly under the quadriceps on the femur/bone just above the knee, keeping the kneecap out of the way during joint function. Some people feel the Articularis genu should be considered a “fifth” Quadricep.

Correct Answer: The Vastus Intermedius is completely hidden under the Rectus Femoris in an ordinary thigh. The Latin name, “vastus,” reflects that the quadriceps are the largest muscles in the human body (just as the knee is the largest joint in the body). (Choose the back arrow and an incorrect answer to see the definitions of lateralis, medialis, and intermedius.)

Correct answer: The Rectus Femoris is attached to two bone sites above the femur, by way of an aponeurosis and tendon structure called the iliofemoral ligament. The tendon-to-bone origin points are located on the anterior (front) inferior iliac spine and the iliac (hip) crest (just above the hip ball and socket. The socket is anatomically shaped like a Roman “little vinegar cup,” and so, in Latin, the socket is called the acetabulum). It is clear that the Rectus Femoris is not attached to the femur on its way down to the knee because the Vastus Intermedius lies underneath it, and that muscle is extensively attached to the femur.

Your answer is correct. Rectus is Latin for straight. Anatomically, straight refers to direction of pull (Gray, Anatomy of the Human Body; see http://www.bartleby.com/107/102.html) , and direction may be identified not only by whether the muscle goes straight from its origin to its end point of insertion, but also by its fiber architecture. Each side of the Rectus Femoris has a “fusiform” or spindle-like fiber structure, a slight variation on a purely straight, or “strap-like” structure. A straight muscle will have a good range of motion.

Your answer is correct. The slant of the muscle fiber bundles (fascicles) of the Vastus Lateralis and Vastus Medialis is the same at their origins near the hip as at their insertions into the Quadriceps Tendon above the knee. Their muscle structure is unipennate (“uni” meaning “one”). Penniform structure provides strength, whereas fusiform structure provides range of motion. Go back and select the incorrect response to see the explanation of why the Rectus femoris and Vastus intermedius are bipennate.

Your answer was correct if you chose either that the fusiform structure provides for range of motion, or that the bipennate structure provides for strength.

You chose the correct answer: The Vastus Intermedius takes up the most space on the anterior (front) femur. However, like the other two Vasti quadriceps muscles, a portion of its origin is also from the posterior femur. The Articularis Genu, sometimes called a fifth quadricep, also has its origin on the front of the femur.

Correct response: The Quadriceps Tendon is an aponeurosis. Pennate muscles, such as the 4 quadriceps, typically merge into an aponeurosis at their points of ORIGIN and INSERTION. An aponeurosis is stronger and stretches more than the tendon into which it thins out. The aponeurosis and tendon can be long and continuous between two sides of a muscle, as in the case of the Rectus Femoris at its origin, or can be long and continuous attached to a bone, as in the case of the Vasti muscles at their origins. The Quadriceps Femoris muscle group merges into a single aponeurosis, called the “Quadriceps Tendon,” prior to thinning into a pure tendon at the point of INSERTION into the patella and patellar tendon.