• What Is The Circulatory System?
|What Is The Circulatory System?
Terminology: Circulatory system is also called the cardiovascular system and circulation system.
The circulatory system is a network of veins and arteries that transport blood around the body. It consists of:
How Does Blood Circulate?
Blood is pumped from the heart (a muscular organ) around the body through a transport system of arteries, veins and capillaries. Our body actually has two closed circulatory systems:
What Is Blood?
Blood is a liquid that circulates the body. It carries oxygen and food to the cells in the body and takes away carbon dioxide and other waste products. It fights infection, keeps you warm and distributes chemicals. See what is blood?, expanded article.
What Is The Heart?
The heart is the centre of the circulatory system (hence the use of the word heart to mean the centre of something in English). If blood is the body's fuel, the heart is its engine.
What Does The Heart Do?
The heart is the pump that drives the whole circulatory system. Its job is to pump blood that is high in oxygen from the lungs to the body and to return blood low in oxygen to the lungs for a refill. This has to be achieved by keeping the low oxygenated blood and high oxygenated blood apart. It they got mixed up, our whole system would fail. This is why the heart is divided into 4 chambers. The heart's action is controlled by the autonomic nervous system.
What Does The Heart Look Like?
It is a hollow red organ, about the size of your fist. It is positioned in the centre of the thorax (breast plate). The heart is composed almost entirely of muscle and is very similar to all the other muscles in the body (like the leg or arm muscles). However, it is specially designed to contract (squeeze) again and again without us having to remember to ‘tell’ it to do so. It has special fibers that act as an electrical system that co-ordinate how often it beats. The heart is divided into four chambers, two on the left and two on the right. Each side has an atrium (plural is atria or auricles) in the upper part, where blood is received and a ventricle in the lower part, where it is pumped out. Atria and ventricles are connected by the atrio-ventricular opening. The septum, a muscular wall, separates the right and left sides of the heart. This prevents deoxygenated blood from the veins on the right coming into contact with oxygenated blood going to the arteries on the left. The heart makes sure that blood flows in the correct direction by the use of one-way heart valves.
What Is A Heartbeat?
A heartbeat (also called cardiac cycle), is one contraction (squeezing) of the heart muscle. For a heartbeat to take place, the following pattern of muscular contraction of the heart wall must take place:
Facts And Statistics
Heartbeat, Heart Rate and Pulse. What's The Difference?
Your heartbeat is when the heart expands and contracts and blood is pumped through its chambers. The average heart beats about 100,000 times in a day. If you place your hand over your heart you can feel your heartbeat. Your heart rate is how many times your heart beats in a minute. You can measure this by taking your pulse. Your pulse is a measurement tool for checking your heart rate.
Is A Heart Rate Always The Same?
The heart rate changes in both healthy and unhealthy bodies, for a variety of reasons. The following all affect it:
|HOW BLOOD IS PUMPED INTO AND OUT OF THE HEART
What Is Pulmonary Circulation?
The circulation of blood from the heart to the lungs and back. Deoxygenated blood travels from the heart to the lungs in the pulmonary artery. The blood gets rid of its carbon dioxide (CO2) and replaces it with oxygen (O2). It then returns to the heart via the pulmonary veins (from lungs to heart) ready to be pumped around the body.
Pulmonary and Systemic Circuit
How Does This Happen?
The right atrium receives deoxygenated blood from the superior vena cava (the vein from the upper body) and the inferior vena cava (the vein from the lower body). The blood then flows into the right ventricle from where it is pumped into the pulmonary artery which divides into the right and left pulmonary arteries (which go to the right and left lungs). Blood reaches the lungs via tiny vessels called capillaries which are porous to gases (see Respiratory System). The lungs remove the carbon dioxide (CO2) from the blood in the capillaries, replace it with oxygen and return the oxygenated blood to the left atrium of the heart through the four pulmonary veins. The blood is pushed by the contraction of the left atrium through the bicuspid valve into the left ventricle. The left ventricle then contracts and pumps the blood through the aorta, which branches to form the ascending and descending aorta, for distribution around the body.
How Is The Direction Of The Blood Correctly Maintained?
The direction of blood is maintained by valves. The atrio-ventricular openings each have a valve: the tricuspid valve on the right and the bicuspid valve on the left. Both these valves allow blood to flow from the atria into the ventricles, but block the atria when the ventricles contract, ensuring that blood continues to circulate in the correct direction. The semi-lunar valves (three pocket-shaped flaps at the vessel's entrance) in the aorta and the pulmonary artery, ensure that there is no back flow from the aorta to the left ventricle or from the pulmonary artery into the right ventricle.
What Is Coronary Circulation?
The heart is, of course, a muscle which needs the benefits of circulation like every other muscle and organ in the body. It has its own circulatory system called coronary circulation. Right and left coronary arteries leave the beginning of the aorta and branch into the heart wall to form a network of capillaries to feed the tissue cells. The blood is then collected back into the coronary veins which empty into the right atrium of the heart. Blockages in these arteries and veins can lead to the heart muscle being starved of nutrients and oxygen - symptoms of which include chest pain, angina and ulimately a heart attack.
|HOW BLOOD IS PUMPED AROUND THE BODY
You now know how blood is pumped into and out of the heart. The following section explains how it travels from the heart around the body.
Systemic circulation is the circulation of blood from the heart to the body. Blood leaves the heart by the aorta, the largest artery in the body, travels throughout the body and returns to the heart through the inferior and superior vena cava (two of the largest veins). An extensive network of arteries, veins and capillaries transports blood to every cell in the body.
What Do Arteries And Veins Do?
Arteries carry oxygenated blood from the heart and veins carry deoxygenated blood to the heart, except in the pulmonary system.
Difference Between Arteries And Veins
Main Veins And Arteries Of The Body
If you have ever visited the doctor, you will probably have had your blood pressure checked. But what is it and how does it affect circulation?
How Does Blood Clot?
If a blood vessel (a capillary, vein or artery) is damaged (internally or externally) bleeding occurs until a clot forms. This clot stops excessive loss of blood from the system. If no blood clot forms it is called a hemorrhage. Expanded article: How does blood clot?
Blood test: How a blood test is performed.
Main causes of death in women: Which disease is most likely to kill you?
|Interrelationships: Working With Other Systems
The Circulatory system links to:
| Other Useful Guides
Recommended Health Screenings For Women: Including Pap smear and mammograms.
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