Final answer:
The soleus is a muscle in the calf region of the lower leg, and the largest muscle in the lower leg is the gastrocnemius. The gastrocnemius and soleus attach to the calcaneus bone by the Achilles tendon.
Step-by-step explanation:
The soleus is a muscle that forms part of the calf region of the lower leg. When discussing the muscles of the lower leg, the largest muscle is the gastrocnemius, which, together with the soleus, forms the calf and is attached to the calcaneus bone via the Achilles tendon as shown in various figures like 9.38 and 9.35.
It is important to differentiate these muscles from those of the gluteal region and thigh, which include the gluteus maximus, medius, and minimus, and other muscles like the sartorius and the gracilis which are involved in movements such as crossing the legs or moving the femur. Moreover, muscles that move the lower leg typically originate on the femur and insert into the bones of the knee joint.