The circulatory system transports oxygen, nutrients, and other  substances throughout the body, and it removes ___________ from tissues.

_{A wall called the _______ separates the right side of the heart from the left side.}

On each side of the septum is an upper and lower chamber. Each upper chamber, or __________ (plural: atria), receives blood from the body. Each lower chamber, or ventricle, pumps blood out of the heart.

On each side of the septum is an upper and lower chamber. Each upper chamber, or atrium (plural: atria), receives blood from the body. Each lower chamber, or ________, pumps blood out of the heart.

The left side of the heart pumps oxygen-rich blood to the rest of the body through the ___________ circulation.

Large vessels, or ________, carry blood from the heart to the tissues of the body.

The thin walls of capillaries allow oxygen and nutrients to diffuse from blood into ___________ and allow carbon dioxide and other waste products to move from ___________ into blood.

After blood passes through the capillaries, it returns to the heart through __________.

Many veins contain ___________, which ensure blood flows in one direction through these vessels toward the heart.