The medullary cavity of a long bone primarily contains:

Photoreceptors are found in the:

Extension of the foot at the ankle is called:

During the cross-bridge cycle, which ion binds to troponin to expose binding sites on actin?

Buffers work by:

This is an image of glandular tissue, stained with H&E stain. The large white circular structures represent what?

Which region of the sarcomere visibly shortens during contraction?

Which pathway uses a two-neuron chain to reach its effector?

Which portion of the brainstem contains nuclei that regulate heart rate and breathing?

In this image of the cortex of the kidney, the structures which are circled are distal convoluted tubules. The distal convoluted tubules empty the ultrafiltrate into what structures?