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Diseases of the heart and circulatory system

Khan: heart diseases and heart attacks

http://www.khanacademy.org/video/heart-disease-and-heart- attacks?playlist=Biology

Khan: thrombo-emboli and thromboembolisms

http://www.khanacademy.org/video/thrombo-emboli-and- thromboembolisms?playlist=Biology

Khan: stenosis, ischemia and heart failure

http://www.khanacademy.org/video/stenosis--ischemia-and-heart- failure?playlist=Biology

Cardiovascular diseases

  • Cardiovascular disorders are a major cause of death in modern societies like heart attacks and strokes .
  • Angina is caused when the heart muscle receives an inadequate supply of blood, resulting in very painful cramps in the chest area.

Heart attack

Cardiac muscle cells are provided with oxygenated blood by a system of coronary arteries . During exercise the flow through these arteries is up to five times normal flow. Blocked flow in coronary arteries can result in death of heart muscle, leadingto a heart attack .

Blockage of coronary arteries is usually the result of gradual buildup of lipids and cholesterol in the inner wall of the coronary artery. Occasional chest paincan result during periods of stress or physical exercise. Angina indicates that oxygen needs are greater than the ability to deliver it and that a heart attack may occur in the future. Heart muscle cells that die are notreplaced since heart muscle cells do not divide. Heart disease and coronary artery disease are the leading causes of death.

The figure below shows development of arterial plaque. Images from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.

Hypertension

Hypertension , high blood pressure (the silent killer), occurs when blood pressure is consistently above 140/90. Causes in most cases are unknown, although stress, obesity, high salt intake,and smoking can add to a genetic tendency. Luckily, when diagnosed, the condition is usually treatable with medicines and diet and exercise

Stroke

What Is a Stroke? What Causes a Stroke?

A stroke is a condition where a blood clot or burst artery or blood vessel interrupts blood flow to an area of the brain. A lack of oxygen and glucose (sugar)flowing to the brain leads to the death of brain cells and brain damage, often resulting in an impairment in speech, movement, and memory.

The outcome after a stroke depends on where the stroke occurs and how much of the brain is affected. Smaller strokes may result in small problems, such as weakness in an arm or leg. Larger strokes may lead to paralysis or death. Many stroke patients are left with weakness on one side of the body, difficulty speaking, and bladder problems.

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Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
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