Cardiovascular and Respiratory Systems

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Unit 5. Body In Action.

Assignment- Task 2. Cardiovascular and Respiratory Systems.

The structure and Function of the Cardiovascular System.

The Cardiovascular system consists of the heart, blood vessels and blood. Oxygen and waste products are carried to and from the tissues and cells of blood. The heart is the mechanism, which allows this by pumping blood around the body through tubes called veins and arteries. The heart pumps continually throughout a person's lifetime to the tune of around 30 million beats per year, that about 2.5 billion in a lifetime, and even when you are asleep it pumps approximately 10 litres of blood a minute through the 60,000 miles of blood vessels which makeup the transport system of the body. The cardiovascular system is one of the most important of all the body systems.

The Heart.

The heart is about the size of a clenched fist and is located in the chest between the lungs with its apex slightly tilted to the left. It is made up of Cardiac muscle and is surrounded by pericardium, which is a fluid filled bag, which reduces friction when the heart beats. The heart is not really heart shaped at all but actually cone shaped. It contains 4 chambers, the left and right atria, which are the upper chambers of the heart, and the left and right ventricles, which are the lower chambers. These form the basis for the two distinct transport circuits of the body, both of which begin and end at the heart:

* The pulmonary circuit which carries blood to and from the oxygen exchange surfaces of the lungs

* Systemic circuit, which involves blood flow to the rest of the body.

The blood collects initially in the atria, which then pumps it to the ventricles. The walls of the atria are relatively thin as they are only passing the blood to the lower chambers, but the ventricles have to have enough power to send the blood around the circuits. As a result, the cardiac muscle in the ventricles is much thicker because more muscular power is needed. The right atrium receives deoxygenated blood from the rest of the body, which it then pumps into the right ventricle. The right ventricle pumps this deoxygenated blood to the lungs where it drops off any waste gases and picks up a fresh load of oxygen in a system of gaseous exchange. This newly oxygenated blood now returns to the heart where it is pumped into the left atrium. This has completed the pulmonary circuit. The left atrium pumps the blood to the left ventricle which then pumps the oxygen rich blood to the organs and tissues of the body. The systemic circuit around the body is much larger then the pulmonary circuit so the left ventricle is the most powerful chamber in the heart with a thicker muscle wall than the other three chambers.
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The heart is divided into left and right by a cell wall called the septum. The heart weighs about 250 grams in adult females and 300 grams in adult males. It is able to contract rythmatically independent of the nerve supply because, it is stimulated by an area of specialised tissue in the right atrium called the sino-atrial node.

Blood Vessels.

The blood vessels are the body's transport network as they allow blood to travel to every part of the body and return to the heart. The system of vessels consists of:

* Arteries: ...

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