The air-exchange chambers of the lungs are tiny sacs called _______, which are surrounded by _______.

Oxygen binds with the molecule called _______ inside _______.

A heart attack can be defined as a complete _______ of a _______.

High-density lipoproteins are regarded as healthy because they carry cholesterol _______.

_______ are the delivery vessels of the car diovascular system.

There are two networks of blood vessels in the body. In one of these, the pulmonary circulation, blood flows between the _______. In the other, the systemic circulation, blood flows between the _______.

The heart’s left atrium and left ventricle function in _______ circulation, while the heart’s right atrium and right ventricle function in _______ circulation.

Cells in the heart’s sinoatrial node function as the heart’s pacemaker thanks to their ability to generate _______.

Blood is composed of formed elements, which are cells and cell fragments, and plasma, which is the _______ portion of blood.

There are three kinds of formed elements: _______, _______, and _______. Plasma, meanwhile, is overwhelmingly composed of _______.

Arteries carry blood _______ the heart, while veins carry blood _______ the heart. The tiny blood vessels called_______ connect arteries to veins.