Guide for Reading:

◆ What is the function of the cardiovascular system?

◆ What role does the heart play in the cardiovascular system?

◆ What path does blood take through the circulatory system?

Cardiovascular System:

The cardiovascular system, or circulatory system, consists of the heart, blood vessels, and blood.

The cardiovascular system carries needed substances to cells and carries waste products away from cells.

Blood carries needed oxygen to cells and carries waste products away from cells.

The Heart:

The heart is a muscular organ that pumps blood throughout the body.

Each time the heart beats, it pushes blood through the blood vessels of the cardiovascular system.

The Heart:

The heart has a right side and a left side. Each side has two compartments, or chambers. Each upper chamber, or atrium, receives blood that comes into the heart. Each lower chamber, or ventricle, pumps blood out of the heart. In each side of the heart, the atrium and ventricle are separated by a valve. A valve is a flap of tissue that prevents blood from flowing backward.

Heart Rate:

The pacemaker in the right atrium sends out signals that make the heart muscle contract. The pacemaker adjusts the heart rate according to the body’s oxygen needs. When the body needs more oxygen, the heart beats faster.

Blood Vessels:

After leaving the heart, blood travels through three kinds of blood vessels. Arteries carry blood away from the heart and into the capillaries. Capillaries are tiny vessels where substances are exchanged between the blood and body cells. Blood flows from capillaries into veins. The veins carry blood back to the heart.

Path of Blood Flow:

The overall pattern of the body’s blood flow consists of two loops. In the first loop,blood travels from the heart to the lungs and then back to the heart. In the second loop, blood is pumped from the heart through the body and then returns again to the heart. 

Path of Blood Flow:

In the first loop, oxygen-poor blood is pumped by the right ventricle to the lungs, where it picks up oxygen. Blood is then carried back to the left atrium.

Path of Blood Flow:

In the other loop, the oxygen-rich blood moves from the left atrium to the left ventricle. The left ventricle pumps the oxygen-rich blood to the rest of the body. Blood leaves the left ventricle through the aorta, the largest artery in the body.

Path of Blood Flow:

After the blood has traveled through the body, oxygen-poor blood comes back to the right atrium of the heart.

Ventricles:

When the ventricle muscles contract, they exert a force on the blood that is inside them. A force is a push or pull.