_____ cells produce fibers that support other cells in lymphoid organs.

On an electrocardiogram, the P wave corresponds with which of the following electrical events?

Around 80% of the volume of blood in the ventricles fills passively; the other 20% depends on _____.

Which of the following lymphoid structures gather and remove pathogens from food and air?

The _____, in the wall of the distal portion of the small intestine are important for destroying bacteria that might try to breach the intestinal wall AND for sampling the gut flora to generate “memory” lymphocytes.

Which of the following acts as the “backup” pacemaker to the heart and is responsible for a 0.1 second delay in impulse transmission?

A blood clot that develops in an unbroken blood vessel and freely floats in the blood stream is known as a:

Blood’s _____ increases with increasing hematocrit.

What is the name of the supportive structure labeled ? What is the name of the structure labeled ?  

Nurses have ranked as the most trusted professional for the past several years in the US.