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Cardiovascular System

HeartAlarm wrist watch HeartAlarm wrist watch The HeartAlarm warns the wearer an hour or more before a heart attack occurs. The HeartAlarm wristwatch works by sensing the electrical signals that the heart produces with each contraction. These signals can be sensed anywhere on the body's surface, including the wrist. When a blood clot blocks the flow of blood in the coronary artery, depriving some heart muscles of oxygen, a different electrical signal is produced. A microcomputer in the HeartAlarm screens the electrical signals, and sounds an alarm only when it receives typical heart attack signals. Let's learn how heart works.

Learning Objectives

After completing the topic, the student will be able to:

  • Delineate the structure and function of heart and vascular system.
  • List the major components of human heart, including the four chambers and four valves.
  • Distinguish the structure and functions of arteries, veins, and capillaries.
  • Examine how the sequential pattern of contraction and relaxation in the heart results in a normal pattern of blood flow.
  • Systematize the path of oxygenated and de‐oxygenated blood flow between heart and lungs.
  • Define “cardiac cycle” and understand the mechanism of blood circulation in the heart.
  • Define “pacemaker of the heart” and discuss how the SA and AV nodes control the contractions of the heart muscle.
  • Describe the way the electrocardiogram (ECG) is recorded, the waves of the ECG, and the relationship of the ECG to the electrical axis of the heart.
  • Name the common cardiac arrhythmias and describe the processes that produce them.
  • Understand the basis of disease states where components of blood and vasculature are abnormal or dysregulated.
  • Explore the different diagnostic resources available for treating cardiovascular diseases.
Location of the heart Location of the heart in the thorax The heart is located in the chest between the lungs behind the sternum and above the diaphragm. It is surrounded by the pericardium. Its size is about that of a fist, and its weight is about 250–300 g. Its center is located about 1.5 cm to the left of the midsagittal plane. Located above the heart are the great vessels: the superior and inferior vena cava, the pulmonary artery and vein, as well as the aorta. The aortic arch lies behind the heart. The esophagus and the spine lie further behind the heart.

The heart, which is about the size of your fist ‐ 12 cm in length and 9 cm in width, is an incredibly efficient organ that works constantly without ever pausing to rest.

Heart is located, right in the centre between the two lungs and above the diaphragm and is made of a unique cardiac muscle. The narrow end of the roughly triangular heart is pointed to the left side and during working, the contraction of the heart is most powerful at this end giving a feeling of the heart being on the left side.

The average weight of a female human heart is 9 ounces and a male's heart is 10.5 ounces. The heart comprises less than 0.5 percent of the total body weight. The heart has three layers. The smooth, inside lining of the heart is called the endocardium. The middle layer of heart muscle is called the myocardium.

It is surrounded by a fluid filled sac with a double walled membranous covering called the pericardium which protects the heart from mechanical injuries, while the lubricating pericardial fluid reduces friction during heart beat.

The heart is a hollow muscle that pumps blood around the body Arteries, carry oxygenated blood around the body. Veins, carry deoxygenated blood back to the heart and lungs. The large artery is the aorta, the large vein is the vena cava.
Blood Circulation

The movement of the blood through the heart and around the body is called circulation and the heart takes less than 60 seconds to pump blood to every cell in your body. Blood delivers oxygen to all the body’s cells and without oxygen these cells would die. The heart is sort of a double pump, which circulates blood around the body to provide the oxygen and nutrients the body needs, while carrying away the waste. The left side of the heart receives oxygen ‐ rich blood from the lungs and pumps it out to every part of the body.

Oxygen from blood reacts with sugar in the cells to make energy and the waste product of this process, carbon dioxide, is carried away from the cells in your blood. Blood needing more oxygen is sent back to the heart to begin the cycle again. The right side of the heart receives oxygen ‐ poor blood from the body and pumps it to the lungs where it unloads carbon dioxide and picks up oxygen.

The right ventricle pumps the blood to the lungs, where carbon dioxide is removed from the blood and sent out of the body when we exhale. A fresh breath of oxygen through inhale enter the blood in the lungs to start the process again. The heart transports all the blood around your body about 1000 times in a day.

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