Resources
Diagram of Blood Flow Around the Heart, Lungs and Body:
For more detailed diagrams of the heart, go to:
http://www.merck.com/mmhe/sec03/ch020/ch020b.html
An animated diagram showing blood flow through the heart:
http://www.pbs.org/wgbh/nova/heart/heartmap.html
Structure of the Heart
- The shape of the human heart is primarily a shell, shaped like an upside-down pear.
- There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria, one on the left and one on the right. The other two are called ventricles, one left and one right. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest.
- A wall, called the septum, separates the right and left sides of the heart.
- There are four valves in the heart that help to direct blood flow. As they open and close, the valves produce sounds that can be heard with a stethoscope. It makes that dub-dub sound. A valve connects each atrium to the ventricle below it. E.g.: the mitral valve connects the left atrium with the left ventricle, and the tricuspid valve connects the right atrium with the right ventricle.
- The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.
- Nerves connected to the heart regulate the speed with which the muscle contracts. The heart's structure makes it an efficient, never-ceasing pump
- The heart pumps from the moment of development through the moment of death, so it has to be strong. As the cardiac muscle contracts it pushes blood through the chambers and into the vessels.
Function of the Heart
- The role of the heart is to deliver the oxygen-rich blood to every cell in the body, which needs oxygen in order to live and function.
- The arteries carry oxygenated blood to the body from the lungs. The largest artery is the aorta, which branches off the heart and then divides into many smaller arteries
- The veins carry the deoxygenated blood from the body back to the lungs to pick up more oxygen, and then back to the heart once again.
- Blood flows continuously through the circulatory system.
- Maintenance of blood volume and circulation is critical to life. Sudden blood loss of more than 30% is fatal, as is slow blood loss of 50%. If the blood does not keep circulating properly blood clots form which can cause death or disability.
- Coronary Arteries supply blood to the heart muscle. Although its chambers contain blood, the heart receives no nourishment from the blood inside the chambers. Two major coronary arteries (the right coronary artery and the left main coronary artery) branch off the aorta, and then divide into many smaller arteries that lie in the heart muscle and feed the heart.
Interesting Facts:
1.The shell
- At any time in your life your heart is about the size of your clenched fist at that time, and an adult heart weighs about 11 ounces (310 grams).
- The heart begins to beat at about four weeks after conception, and is fully developed at about eight weeks, when the embryo is only about one inch long.
- Your heart is located in the middle of your chest behind your breastbone.
- The average heart's muscle contracts and relaxes about 70 to 80 times per minute, you can feel this beat (pulse) on the inside of your wrist.
- Your heart beats over 100,000 times a day, or more than two and a half billion times in an average lifetime.
- Exercise makes your heart beat faster, resting makes your heart beat slower.
2.The Right ventricle
- R ventricle receives de-oxygenated blood from the R atrium and directs it to the lungs for re-oxygenation.
- Every minute, the heart pumps your entire supply of blood - about five quarts - through the body.
- In one year the average humanheart circulates about 1.6 million gallons of blood through the body, or about 4300 gallons of blood a day.
- In a 70-year lifetime, it pumps about 51 million gallons!
3.The Left ventricle
- L ventricle receives oxygenated blood from the lungs via the L atrium and directs it to the arteries for distribution around the body.
- The left ventricle is the strongest chamber and contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.
- The left ventricle creates enough pressure when it pumps blood out to the body to squirt blood 30 feet.
- The heart muscle and can perform enough work in one hour to lift 3,000 pounds, roughly the weight of a small car, about one foot off the ground.
- All the blood vessels in the body joined end to end would stretch 62,000 miles or two and a half times around the earth.
4.The Right Atrium
- R atrium receives de-oxygenated blood from the body via the veins and directs it to the R ventricle.
- Veins are thin walled and return de-oxygenated blood to the heart.
- They can store blood by swelling up, and have valves to prevent backflow.
- Veins contain 70% of your blood, which is less than 70% saturated with oxygen.
5.The Left Atrium
- L atrium receives oxygenated blood from the lungs and directs it to the L ventricle for distribution around the body via arteries.
- Arteries are thick walled and move oxygenated blood around the body.
- Arteries recoil after each heart beat helping to propel blood along.
- Arteries contain 17% of the blood, which is 98% saturated with oxygen.
- Red blood cells make approximately 250,000 round trips of the body, carrying oxygen to the 60 trillion other body cells.
- Red blood cells live for about 4 months before returning to the bone marrow, where they were born, to die
Links to Other Resources
http://worldinvisible.com/apologet/humbody/heart.htm
Good information for children with static diagrams
http://users.tpg.com.au/users/amcgann/body/circulatory.html
Educational information for children with static diagrams
http://www.merck.com/mmhe/sec03/ch020/ch020b.html
Information and clear static diagrams of the heart structure.
http://www.pbs.org/wgbh/nova/heart/heartmap.html
Gives basic information and an animated diagram showing blood flow through the heart.
http://www.bbc.co.uk/science/humanbody/body/factfiles/heart/heart.shtml
Good interactive website for 12-16 yr old children
http://www.medtropolis.com/VBody.asp
A very visual, interactive site with animated diagrams and a narrated tour. Requires a faster internet connection.
http://www.lung.ca/children/index_kids.html
Offers separate sections for students in grades 1-3, 4-6 and 7-12 about the heart and lungs. Static diagrams.
http://mann.sandi.net/resources/body%20folder/body%20systems%20webquest%20new.htm
Questions and answers for children, including the circulatory system
http://www.americanheart.org/ American Heart Association
Contains further information, mostly on heart disease.
www.smm.org/heart/heart/top.html
An animated and interactive site for grades 4 to 8. Students can watch the flow of blood to and from the heart, use a virtual stethoscope, and watch heart valves at work. Includes a heartbeat calculator, video of heart surgery and nearly a dozen lesson plans.
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