1. The Circulatory System
Mrs. Legro’s 6th Grade Science

2. Objectives & Vocabulary
Compare and contrast arteries, veins and capillaries.
Explain how blood moves through the heart.
Identify the functions of the pulmonary and systemic circulation systems.
Vocabulary Words
Atrium
Ventricle
Coronary circulation
Pulmonary circulation
Systemic circulation
Artery
Vein
Capillary

3. What is The Circulatory System?
Also referred to as the “Cardiovascular System”
Makes up the network that delivers blood to the body’s tissues.
With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to all of our cells.
It is divided into three sections:
Coronary circulation: heart
Pulmonary circulation: heart to lungs
Systemic circulation: heart to body
The beating of your heart controls blood flow through each section.

4. Coronary Circulation: Heart
The heart is the key organ of the circulatory system
Main function is to propel blood throughout the body
Usually beats 60 – 100 times per minute
More than 30 million times per year
About 2.5 billion times in a 70-year lifetime.
If coronary circulation is blocked, oxygen and nutrients can’t reach all the cells of the heart. This can result in a heart attack.

5. Anatomy of the Heart
The heart consists of 4 compartments called chambers:
Two upper chambers: right and left atriums (atria).
Receive the blood entering the heart.
Two lower chambers: right and left ventricles.
Pumps blood out of the heart.
These valves separate the ventricles and atria:
The tricuspid valve separates right atrium from right ventricle.
The mitral valve separates left atrium from left ventricle.
Two other important valves:
Pulmonary valve: It is a one-way valve that allows blood to leave the heart via the arteries. It’s opened by the increased blood pressure (systole).
Aortic valve: It is a one-way valve that lets blood from the LV be pumped up (ejected) into the aorta.
All valves are one-way
The interatrial septum: A wall prevents blood from flowing between the two atriums and two ventricles.
Keeps blood rich in oxygen separated from the blood low in oxygen.
A wall, the interventricular septum, divides the ventricles.
If the two bloods mixed, your body’s cells would not get all the oxygen they need.
The atrioventricular valves separate the atria from the ventricles.

6. Anatomy of the Heart The heart has two main veins:
Superior Vena Cava: this large vein carries deoxygenated blood into the heart from the upper portion of the body and empties into the right atrium.
Inferior Vena Cava: this large vein carries deoxygenated blood into the heart from the lower portion of the body and empties into the right atrium.
Pulmonary Artery: deoxygenated blood that enters here is carried to the lungs.
Pulmonary Vein: Oxygenated blood returns to the heart via the pulmonary veins.
Aorta: the body’s largest artery. It supplies oxygenated blood to the circulatory system.

7. Pulmonary Circulation
It is the flow of blood through the heart to the lungs and back to the heart. It carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated blood back to the heart.

8. Systemic Circulation
The movement of oxygen-rich blood to all of your organs and body tissues (except heart and lungs)
It is the largest of the three sections of your circulatory system.

9. How Systemic Circulation Works
Oxygen-rich blood flows from your heart in the arteries of this system.
Then nutrients and oxygen are delivered by blood to your body cells and exchanged for carbon dioxide and wastes.
Finally, the blood returns to your heart in the veins of the systemic circulation system.

10. Arteries, Veins, Capillaries
Arteries are blood vessels that carry blood away from the heart.
Thick, elastic walls made of connective tissue and smooth muscle tissue.
Each ventricle of the heart is connected to an artery.
Every time your heart contracts, blood is moved from your heart into arteries.
You can see capillaries when your eyes are bloodshot. They are the tiny red lines you see in the white area of your eye.

11. Arteries, Veins, Capillaries
Arterial walls have three layers:
Endothelium: is on the inside and provides a smooth lining for blood to flow over as it moves through the artery.
Media: is the middle part of the artery, made up of a layer of muscle and elastic tissue.
Adventitia: is the tough covering that protects the outside of the artery.
Veins have the same three layers as arteries, but veins are thinner and less flexible.

12. Arteries, Veins, Capillaries
Veins are the blood vessels that carry blood back to the heart.
They contain valves that prevent blood from flowing backward.

13. Arteries, Veins, Capillaries
Capillaries are microscopic blood vessels that connect arteries and veins.
The walls are very thin - only one cell thick.
Nutrients and oxygen diffuse into body cells through the thin capillary walls.
Waste materials and carbon dioxide diffuse from body cells into the capillaries.

14. Putting it all together…

15. How Does the Heart Work?
One complete heartbeat makes up your cardiac cycle, which consists of 2 phases.
First phase is the ventricles contracting. This is called systole.
This sends blood into pulmonary and systemic circulation.
The second phase is when your ventricles relax. This is called diastole.
This causes the ventricles to fill with blood from the atria.
The cycle then starts again.

16. Your Heart is an Electrical Machine!
An electrical system in the heart causes it to beat in its regular rhythm.
The SA node (sinoatrial node) is a small area of tissue in the wall of the right atrium. The SA node sends out an electrical signal to start the contracting of the heart muscle.
These electrical impulses cause the atria to contract first.
The electrical impulses then travel down to the AV node (atrioventricular node), which acts like a relay station.
From here, the electrical signal travels through the right and left ventricles, causing them to contract and force blood out into the major arteries.

17. How Does the Blood Flow?
Oxygen-poor blood fills the RA and then flows to the RV, where it is pumped to the lungs through the PA’s.
The lungs refresh the blood with a new supply of oxygen, which comes from the air you breathe in.
The now oxygen-rich blood, returns from the lungs and enters the LA. The oxygen-rich blood then flows from the LA to the LV.
RA: Right Atrium
RV: Right Ventricle
PA: Pulmonary Artery
LA: Left Atrium
LV: Left Ventricle
The blood is then pumped through the main artery that supplies blood to the body, called the aorta, to supply tissues throughout your body with oxygen.
Each valve opens and closes one time per heart beat.
A beating heart contracts and relaxes.
Your heart is nourished by blood, too. Oxygen-rich blood is delivered by coronary arteries that extend over the surface of your heart.

18. How Does the Blood Flow?

20. Things That Can Go Wrong
Cardiovascular Disease: any disease that affects the heart, blood vessels and blood.
Atherosclerosis: Fatty deposits build up on arterial walls. This can happen by eating foods high in cholesterol and saturated fats.
If a coronary artery is blocked, a heart attack can occur.
Hypertension: Also known as high blood pressure. When blood pressure is higher than normal most of the time, extra strain is placed on the heart-the heart has to work harder to keep blood flowing.
Atherosclerosis can cause hypertension.
Heart Failure: This occurs when the hear cannot pump blood efficiently.
May be caused when heart muscle tissue is weakened by disease or when heart valves do not work properly.
Atherosclerosis can cause hypertension because a clogged artery can increase pressure within the vessel. The walls become stiff and hard, like a metal pipe. The artery walls no longer contract and dilate easily because they have lost their elasticity.

21. What Does Atherosclerosis Look Like?