All of the following mechanisms assist veins inreturning blood to the heart EXCEPT ______.

A piece of a clot that moves from where it formed and can block another vessel elsewhere is termed _________.

Carbonic anhydrase catalyzes the reaction of carbon dioxide and water to form ______.

Which of the following is an example of chemical digestion?

An innate, nonspecific defense against the action of viruses that cells infected with viruses can produce is ___________.

The chemoreceptors that send sensory input to the respiratory centers are found in the following locations exceptthe ______.

The nutrient(s) required for the production of hemoglobin include ______.

An organic compound that the body needs in minute amounts is a __________.

When the right atrium contracts, the ______.

_________ are primarily used as an energy source, but unused quantities are converted into _________ and stored.