The circulatory system:
The circulatory system is made up of the vessels and the muscles that help and control the flow of the blood around the body. This process is called circulation. The main parts of the system are the heart, arteries, capillaries and veins. As blood begins to circulate, it leaves the heart from the left ventricle and goes into the aorta. The aorta is the largest artery in the body. The blood leaving the aorta is full of oxygen. This is important for the cells in the brain and the body to do their work. The oxygen rich blood travels throughout the body in its system of arteries into the smallest arterioles. On its way back to the heart, the blood travels through a system of veins. As it reaches the lungs, the carbon dioxide (a waste product) is removed from the blood and replace with fresh oxygen that we have inhaled through the lungs.
The heart is a muscle about the size of an adult fist. It is composed of two sides and four chambers: the left and right atria and the left and right ventricles. The two atria are located on the top of the heart and receive blood from various parts of the body. The two ventricles are located on the bottom of the heart and pump blood away from the heart, to the body. The right ventricle is responsible for pumping deoxygentated blood to the lungs. The left ventricle pumps oxygenated blood to the rest of the body. Between the chambers are valves. Valves control the flow of blood, insuring that it flows in one direction.
The Blood Vessels
Blood vessels are a series of elastic tubing that carry blood to and from the heart. Oxygenated blood leaves the heart and supplies oxygen and nutrients to the body via the arteries. After crossing capillaries, veins return deoxygenated blood and waste products to the heart through the vena cava. After leaving the right ventricle through the pulmonary arteries, the blood gets oxygenated in the lungs, disposes of carbon dioxide from the body, returns to the left atrium from the pulmonary vein and then to the left ventricle to repeat the process again.
Blood is a semi-viscous fluid that contains red blood cells, white blood cells, platelets and a watery substance called plasma that contains proteins, sugars, fats and minerals. The average adult body circulates 10 pints of blood through a cardiac cycle. The red blood cells contain hemoglobin, which is responsible for transporting oxygen to the cells and carries carbon dioxide back to the heart.
Cardiovascular function and control
The electrocardiogram (ecg)
The electrocardiogram (ECG or EKG) is a diagnostic tool that is routinely used to assess the electrical and muscular functions of the heart. While it is a relatively simple test to perform, the interpretation of the ECG tracing requires significant amounts of training. Numerous textbooks are devoted to the subject. The heart is a two stage electrical pump and the heart's electrical activity can be measured by electrodes placed on the skin. The electrocardiogram can measure the rate and rhythm of the heartbeat, as well as provide indirect evidence of blood flow to the heart muscle. A standardized system has been developed for the electrode placement for a routine ECG. Ten electrodes are needed to produce 12 electrical views of the heart. An electrode lead, or patch, is placed on each arm and leg and six are placed across the chest wall. The signals received from each electrode are recorded. The printed view of these recordings is the electrocardiogram. By comparison, a heart monitor requires only three electrode leads – one each on the right arm, left arm, and left chest. It only measures the rate and rhythm of the heartbeat. This kind of monitoring does not constitute a complete ECG.
The cardiac cycle
The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the...