This type of vessel has a wall made up of only simple squamous epithelium, which is perfectly suited for diffusion.

This is the largest heart chamber:

What is the key structure in the vessels closest to the heart that allows these vessels to expand and contract to allow pulses of blood to move through and maintain blood pressure gradients?

This molecule binds to oxygen in the lungs and helps carry it to cells:

Blood moves from an area of high pressure to an area of lower pressure.  That is the mechanism that powers blood to deliver nutrients and oxygen to cells.  What structure creates the pressure gradient?

Which of the following are uses of glucose that we get from our diet?

During days 0-5 of the uterine cycle, which hormone is low?

Match the hormone with its action:

Most digestion of food occurs in the ________________.  Most absorbtion of food occurs in the ______________.  

Which of these hormones: moves through the blood with help from a protein and can move directly over the plasma membrane of the target cell without the help of a transport protein?