Dissectible Me 5 minute anatomy

The midbrain is the upper part of the brainstem. In here we find tracts running to and from the spinal cord and cerebrum. We find nuclei and groups of neurones such as the substantia nigra, red nucleus, periaqueductal grey, colliculi and reticular formation. Cranial nerves III and IV come out of the brainstem. What do all of these things do? What does all this mean? 

Quadriceps femoris and the hamstrings are powerful extensors and flexors of the knee respectively, but they also cross the hip joint. Let's talk about their anatomy. 

The pelvic floor (or pelvic diaphragm) describes the structures at the lowest point of the pelvis, largely muscles, that support the pelvic organs directly and everything else inside the torso. Let's explain concisely the important anatomy here.

The flexor tendons of the fingers run into synovial tunnels that let them move freely as we strengthen and relax our grip. These tunnels are tied down to the bone by some extraordinarily strong annular and cruciform pulleys that keep the tendons close to the bone. Let's describe their anatomy and their naming. 

There are 3 arches in the foot: a medial longitudinal arch, a lateral longitudinal arch and a transverse arch. Why do humans have arches in their feet? What's the anatomy here?