Cardiovascular System

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Introduction •

The cardiovascular system or sometimes that have also been known a as the blood vascular system or the simply circulatory is composed by : 1. Heart 2. Blood Vessels @ Vasculature 3. Cells and Plasma that make up the blood for our body.

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The blood vessels of the body represents a closed delivery system that have functions to : 1. Transports blood around the body. 2. Circulating substances such as oxygen, carbon dioxide, nutrients, hormones and waste products.

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There are 3 mains types of blood vessels such as veins, arteries, and capillaries.

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The principles function of the heart is to continuously pump blood around the cardiovascular system and body. It receives the both of sympathetic and parasympathetic nerve fiber which alter the rate of the beat.

The vital sign of the cardiovascular system is to maintaining homeostasis which depends on the continuous and controlled movement of blood through the thousand of miles capillaries that penetrate every tissue and reach every cell in the body.

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Objectives ⇒ Describe the size and location of the heart, including its base and apex. ⇒ Describe the vessels that supply blood to cardiac muscle. ⇒ Describe the valves and its functions. ⇒ What is the function of the conduction system of the heart? ⇒ Starting with SA node, describe the route taken by an action as it goes through the conducting system of the heart.

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Rough descriptive image of human heart 1. The human heart is shaped like an upside-down pear and is located slightly to the left of center inside the chest cavity. 2. About the size of a closed fist, the heart is made primarily of muscle tissue that contracts rhythmically to propel blood to all parts of the body. 3. It typically weighs about 325±75g in men and 275 ± 75 g in women. 4. The heart can be described as having three surfaces and an apex. 5. About two thirds of the heart is to the left of the mid-line. 6. The anterior surface of the heart is formed mainly by the right ventricle and is in contact with the ribs and sternum. 7. The inferior surface of the heart is formed mainly by the left ventricle and is in contact with the diaphragm. 8. The posterior surface of the heart is formed mainly by the left atrium. 9. This surface is also known as the base of the heart. 10.The apex which is anterior to the rest of the heart consists only of the left ventricle and forms an important clinical landmark when assessing the size of the heart. 11.The aorta and the pulmonary trunk arise from the left and right ventricles respectively at the superior pole of the heart 12.The superior and inferior vena cavae open into the upper and lower parts of the right atrium. 13.There are four pulmonary veins which open into the back of the left atrium. 14.The junction between the atria and the ventricles is marked by the atrioventricular groove and the junction between the ventricles both posteriorly and anteriorly is marked by the interventricular grooves.

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Base of the Heart 1. Base of the heart, directed upward, backward, and to the right, is separated from the fifth, sixth, seventh, and eighth thoracic vertebra by the esophagus, aorta, and thoracic duct. 2. It is formed mainly by the left atrium, and, to a small extent, by the back part of the right atrium. 3. Somewhat quadrilateral in form, it is in relation above with the bifurcation of the pulmonary artery, and is bounded below by the posterior part of the coronary sulcus (groove or fissure), containing the coronary sinus. 4. On the right it is limited by the sulcus terminalis of the right atrium, and on the left by the ligament of the left vena cava and the oblique (pertaining to muscles running obliquely in the body as opposed to those running transversely or longitudinally) vein of the left atrium. 5. The four pulmonary veins, two on either side, open into the left atrium, while the superior vena cava opens into the upper, and the anterior vena cava into the lower, part of the right atrium.

Apex of the heart 1. Apex of the heart is the lowest superficial part of the heart. 2. It is directed downward, forward, and to the left, and is overlapped by the left lung and pleura. 3. It lies behind the fifth left intercostals space, 8 to 9 cm. from the mid-sternal line, slightly medial to the midclavicular line.

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5 4. Alternately, it can be found about 4 cm. below and 2 mm. to the medial side of the left mammary papilla. 5. Its function is to pump blood to left atrium.

Vessels that supply blood to cardiac muscle 1. The heart is nourished not by the blood passing through its chambers but by a specialized network of blood vessels. Known as the coronary arteries, these blood vessels encircle the heart like a crown. 2. About 5 percent of the blood pumped to the body enters the coronary arteries, which branch from the aorta just above where it emerges from the left ventricle. 3. Three main coronary arteries—the right, the left circumflex, and the left anterior descending—nourish different regions of the heart muscle. 4. From these three arteries arise smaller branches that enter the muscular walls of the heart to provide a constant supply of oxygen and nutrients. 5. Veins running through the heart muscle converge to form a large channel called the coronary sinus, which returns blood to the right atrium.

Heart Valves Heart valves are valves in the heart that maintain the unidirectional flow of blood by opening and closing depending on the difference in pressure on each side.

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Mitral Valve 1. The

mitral

valve

(also

known

as

the

bicuspid

valve

or

left

atrioventricular valve), is a dual flap (bi = 2) valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). 2. In Latin, the term mitral means shaped like a miter, or bishop's cap. 3. The mitral valve and the tricuspid valve are known collectively as the atrioventricular valves because they lie between the atria and the ventricles of the heart and control flow.

Tricuspid Valve 1. The tricuspid valve is on the right side of the heart, between the right atrium and the right ventricle. 2. The normal tricuspid valve usually has three leaflets and three papillary muscles.

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7 3. Tricuspid valves may also occur with two or four leaflets, and the number may change during life.

Aortic Valve 1. The aortic valve is one of the valves of the heart. 2. It lies between the left ventricle and the aorta. 3. The aortic valve has three cusps. 4. These cusps are half moon shaped hence also called aortic semi lunar valve. 5. Each cusp has a small swelling in the center called the nodule. 6. Dilatation of the wall of the aorta behind these cusps is called aortic sinus. 7. When the aortic valve is open, the normal size of the orifice is 3-4 cm² in adults. 8. During ventricular systole, pressure rises in the left ventricle. 9. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. 10.When ventricular systole ends, pressure in the left ventricle rapidly drops. 11.When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close. 12.The closure of the aortic valve contributes the component of the second heart sound (S2).

Pulmonic Valve 1. Pulmonic valve is the semi lunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. 2. Similar to the aortic valve, the pulmonic valve opens in ventricular systole, when the pressure in the right ventricle rises above the pressure in the pulmonary artery.

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8 3. At the end of ventricular systole, when the pressure in the right ventricle falls rapidly, the pressure in the pulmonary artery will close the pulmonic valve. 4. The closure of the pulmonic valve contributes the component of the second heart sound (S2). 5. The right heart is a low-pressure system, so the component of the second heart sound is usually softer than the component of the second heart sound. 6. However, it is physiologically normal in some young people to hear both components separated during inhalation.

Generation

of

the

Heartbeat 1. Unlike most muscles, which rely on nerve impulses to cause them to contract, heart muscle can contract of its own accord. 2. Certain heart muscle cells have the ability to contract spontaneously, and these cells generate electrical signals that spread to the rest of the heart and cause it to contract with a regular, steady beat. 3. The heartbeat begins with a small group of specialized muscle cells located in the upper right-hand corner of the right atrium. 4. This area is known as the sinoatrial (SA) node. 5. Cells in the SA node generate their electrical signals more frequently than cells elsewhere in the heart, so the electrical signals generated by the SA node synchronize the electrical signals traveling to the rest of the heart. 6. For this reason, the SA node is also known as the heart’s pacemaker. 7. Impulses generated by the SA node spread rapidly throughout the atria, so that all the muscle cells of the atria contract virtually in unison.

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9 8. Electrical impulses cannot be conducted through the partition between the atria and ventricles, which is primarily made of fibrous connective tissue rather than muscle cells. 9. The impulses from the SA node are carried across this connective tissue partition by a small bridge of muscle called the atrioventricular conduction system. 10.The first part of this system is a group of cells at the lower margin of the right atrium, known as the atrioventricular (AV) node. 11.Cells in the AV node conduct impulses relatively slowly, introducing a delay of about two-tenths of a second before an impulse reaches the ventricles. 12.This delay allows time for the blood in the atria to empty into the ventricles before the ventricles begin contracting. 13.After making its way through the AV node, an impulse passes along a group of muscle fibers called the bundle of His, which span the connective tissue wall separating the atria from the ventricles. 14.Once on the other side of that wall, the impulse spreads rapidly among the muscle cells that make up the ventricles. 15.The impulse travels to all parts of the ventricles with the help of a network of fast-conducting fibers called Purkinje fibers. 16.These fibers are necessary because the ventricular walls are so thick and massive. 17.If the impulse had to spread directly from one muscle cell to another, different parts of the ventricles would not contract together, and the heart would not pump blood efficiently. 18.Although this complicated circuit has many steps, an electrical impulse spreads from the SA node throughout the heart in less than one second. 19.The journey of an electrical impulse around the heart can be traced by a machine called an electrocardiograph. 20.This instrument consists of a recording device attached to electrodes that are placed at various points on a person’s skin. 21.The recording device measures different phases of the heartbeat and traces these patterns as peaks and valleys in a graphic image known as an electrocardiogram (ECG, sometimes known as EKG).

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10 22.Changes or abnormalities in the heartbeat or in the heart’s rate of contraction register on the ECG, helping doctors diagnose heart problems or identify damage from a heart attack.

PICTURES & DIAGRAM

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Conclusion As a nurse, we must know anything related to the functions of body systems that appear to be a big factor in their health maintainence. Their organization of body system must well corporated in performing functions to be a well-health human being. As a Pacemaker of our life, cardiac system may be the most important in many people’s thought. As for the heart, it is the main criteria that involves in determining “is this people healthy enough?”. We, as a professional nurses must enrich ourselves in getting deeper into this contribution – aiming at people awareness of their heart importance to their life. Is it difficult to handle that responsible? Think about it, you’ll save dozens of life if you improve your readings and enrich your beautiful knowledge if you search for more about our heart. After then, we can conduct our instrument and well known about their usage especially reading the ecg (electrocardiograph) and get used to the steps using the electrocardiogram machine. Also, we can identify the different sounds of the heart by using stethoscope or only by using our bare hands by doing palpation.

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References: Allison, T. G., D. E. Williams, et al. (1995). Medical and economic costs of psychologic distress in patients with coronary artery disease. Mayo Clinic Proceedings 70(8): 734-742. Beale, N. and S. Nethercott (1986) Job loss and health – the influence of age and previous morbidity. Journal of the Royal College of General Practitioners 36:261-264. Cantin, M. and J. Genest. (1986). The heart as an endocrine gland. Clinical and Investigative Medicine 9(4): 319-327. Childre, D. (1992). Self Empowerment: The Heart Approach to Stress Management. Boulder Creek, CA, Planetary Publications. Lacey, J. I. and B. C. Lacey (1978). Two-way communication between the heart and the brain: Significance of time within the cardiac cycle. American Psychologist (February): 99-113. Lewis, T. (1918). The Soldier’s Heart and the Effort Syndrome. London, Shaw. Grossarth-Maticek, R. and H.J. Eysenck (1995). Self-regulation and mortality from cancer, coronary heart disease and other causes: A prospective study. Personality and Individual Differences 19(6): 781 – 795. Sandman, C. A., B. B. Walker, et al. (1982). Influence of afferent cardiovascular feedback on behavior and the cortical evoked potential. In: J. Cacioppo, J. T. and R. E. Petty, eds. Perspectives in Cardiovascular Psychophysiology. New York, The Guilford Press. Umetani, K., D. H. Singer, et al. (1998). Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades. Journal of the American College of Cardiology 31(3): 593-601.

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