1. The Body’s Transport System
Section 1

2. The Cardiovascular System
The cardiovascular system consists of the heart, blood vessels, and blood.
The cardiovascular system is also known as the circulatory system.
It carries needed substances to cells and carries waste products away from cells. In addition, blood contains cells that fight disease.

3. Delivering Needed Materials
Most substances that need to get from one part of the body to another are carried by blood.
Blood carries oxygen from your lungs to your other body cells.
Blood transports glucose that your cells use to produce energy.

4. Removing Waste Products
The cardiovascular system picks up waste from cells.
When cells break down glucose, they produce carbon dioxide as a waste product. The carbon dioxide is carried through blood to the lungs and is exhaled.

5. Fighting Disease
The cardiovascular system transports cells that attack disease-causing microorganisms.
This helps keep you from being sick by killing the microorganisms and helping to get you well.

6. The Heart
The heart is a hollow, muscular organ that pumps blood throughout the body.
The heart is in the middle of your chest, behind you sternum and rib cage.
Each time the heart beats, it pushes blood through the blood vessels of the cardiovascular system.

7. The Heart

8. The Heart’s Structure
The heart has a right side & a left side that are completely separated by a wall of tissue called the septum.
Each side has two chambers, upper and lower.
The upper chamber is called the atrium which receives blood that come into the heart.
The lower chamber is called the ventricle which pumps blood out of the heart.
The atrium and ventricle are separated by a valve, which is a flap of blood that prevents blood form flowing backward.

9. How the Heart Works The heart has 2 main phases-
Phase one, the heart muscles relax and fills with blood.
Phase two, the heart muscles contract and pumps blood forward.
Your heartbeat is the pumping phase.
When the heart relaxes, blood flows into the chambers. When it contracts, it sends blood from the atria through the valve to the ventricles. The valves snap closed.
This all happens in less than a second.

10. Regulation of Heartbeat
A group of heart cells called the pacemaker sends out signals that make the heart muscle contract.
The pacemaker is located in the right atrium.
The pacemaker receives messages about the body’s oxygen needs and adjusts your heart rate to match.
While you are sitting quietly, you need much less oxygen than you do while you are exercising.

11. Two Loops
After leaving your heart, blood travels in blood vessels through the body.
Your body has 3 kinds of blood vessels:
Arteries: blood vessels that carry blood away from the heart
Capillaries: Tiny, narrow vessels where substances are changed between the blood and body cells.
Veins: blood vessels that carry blood back to your heart.
The flow of blood looks like a figure 8, with the heart in the middle.
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 throughout the body and back to the heart again.

12. Loop One
When blood from the body flows into the right atrium, it contains little oxygen but a lot of carbon dioxide. It is dark red in color due to the lack of oxygen.
The oxygen-poor blood goes from the right atrium to the right ventricle and then is pumped into the arteries that lead to the lungs.
Blood in the lungs flow through tiny capillaries that are oxygen-rich. Oxygen moves from the lungs to the blood and the carbon dioxide in blood moves in the opposite direction.
The blood becomes bright red due to the oxygen. It then flows to the left side of the heart and will be pumped through the second loop.

13. Loop Two
The second loop begins as the left atrium fills with oxygen-rich blood from the lungs.
The blood moves into the left ventricle and is then pumped into the aorta.
The aorta is the largest artery in the body.
This blood flows through tiny capillaries to different parts of your body such as the brain, lungs, and legs.
Oxygen from the blood from moves into the body cells and carbon dioxide from the body cells move into the blood.
The blood becomes oxygen-poor again, sending it back to the right atrium and beginning the process again.

14. The Two Loops