The Circulatory System

The Circulatory System

The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart.

The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide. These roadways travel in one direction only, to keep things going where they should.

The Heart

​The heart is a pump, usually beating about 60 to 100 times per minute. With each heartbeat, the heart sends blood throughout our bodies, carrying oxygen to every cell. After delivering the oxygen, the blood returns to the heart. The heart then sends the blood to the lungs to pick up more oxygen. This cycle repeats over and over again

The heart has four chambers — two on top and two on bottom:

• The two bottom chambers are the right ventricle and the left ventricle. These pump blood out of the heart. A wall called the interventricular septum is between the two ventricles.

• The two top chambers are the right atrium and the left atrium. They receive the blood entering the heart. A wall called the interatrial septum is between the atria.

Multiple Choice

How many chambers are in the heart?

• 1

• 2

• 3

• 4

Two pathways come from the heart:

• The pulmonary circulation is a short loop from the heart to the lungs and back again.

• The systemic circulation carries blood from the heart to all the other parts of the body and back again.

Parts of the circulatory system

• The pulmonary artery is a big artery that comes from the heart. It splits into two main branches, and brings blood from the heart to the lungs. At the lungs, the blood picks up oxygen and drops off carbon dioxide. The blood then returns to the heart through the pulmonary veins.

Next, blood that returns to the heart has picked up lots of oxygen from the lungs. So it can now go out to the body. The aorta is a big artery that leaves the heart carrying this oxygenated blood. Branches off of the aorta send blood to the muscles of the heart itself, as well as all other parts of the body. Like a tree, the branches gets smaller and smaller as they get farther from the aorta.

Multiple Choice

What is the name of the large artery that carries oxygenated blood through the body?

• Pulmonary Artery

• Aorta

• Coronary Artery

• Vena Cava

Arteries and veins are two of the body's main types of blood vessels. Arteries are blood vessels that carry oxygen-rich blood away from the heart to the body. Veins are blood vessels that carry blood that is low in oxygen from the body back to the heart for reoxygenation

Veins VS Arteries

Multiple Choice

What carries low oxygenated blood?

• Veins

• Artieries

• Capillaries

• Bronchis

At each body part, a network of tiny blood vessels called capillaries connects the very small artery branches to very small veins. The capillaries have very thin walls, and through them, nutrients and oxygen are delivered to the cells. Waste products are brought into the capillaries.

Capillaries then lead into small veins. Small veins lead to larger and larger veins as the blood approaches the heart. Valves in the veins keep blood flowing in the correct direction. Two large veins that lead into the heart are the superior vena cava and inferior vena cava. (The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.)

Once the blood is back in the heart, it needs to re-enter the pulmonary circulation and go back to the lungs to drop off the carbon dioxide and pick up more oxygen.

Multiple Choice

What part of the circulatory system is the transition between arteries and veins?

• Arterioles

• Venules

• Capillaries

• Atria

• transporting oxygen and nutrients to the lungs and tissues

• forming blood clots to prevent excess blood loss

• carrying cells and antibodies that fight infection

• bringing waste products to the kidneys and liver, which filter and clean the blood

​Major Functions of Blood

Multiple Choice

What is NOT a function of Blood

• Transport Oxygen

• Carry Waste

• Make Clots

• make nutirents