HEART position of heart & functions of the heart

Explain about anatomy & physiology of heart

1. Physiology Of The Heart BY T,C.Kaviya Assistance Professor Department of Hospital Administration

2. Introduction : The physiology of the heart refers to the study of how the heart functions to pump blood, deliver oxygen and nutrients to tissues, and maintain circulatory homeostasis in the body. It involves the electrical and mechanical processes that control heart activity, blood flow, and coordination between the heart's chambers .

3. Location: Thoracic cavity (chest cavity) Medial (middle) andanterior (front) part of the thorax Between the lungs, slightly offset to the left4. Behind the sternum (breastbone) and ribcage5. In front of the trachea, esophagus, and spine

4. Size: Adult heart: Approximately 12 cm (5 inches) long, 8 cm (3 inches) wide, and 6 cm (2.5 inches) thick Weight: Approximately 250-300 grams (8.8-10.6 ounces)3. Volume: Approximately 500-600 milliliters (17-20 ounces)

5. Heart Position : Obliquely placed, with the apex pointing downwards and to the left Slightly rotated to the left, with the right border parallel to the sternum

6. Structure of the Heart Chambers of the heart: The heart is a muscular organ with four chambers: Right Atrium : Receives deoxygenated blood from the body via the superior and inferior vena cava. Right Ventricle : Pumps deoxygenated blood to the lungs via the pulmonary artery. Left Atrium : Receives oxygenated blood from the lungs via the pulmonary veins. Left Ventricle : Pumps oxygenated blood to the rest of the body via the aorta. The heart also contains valves (tricuspid, mitral, pulmonary, and aortic) that prevent backflow and ensure the unidirectional flow of blood.

7. Chambers ot the heart: The heart is made up of three distinct layers, each serving a specific function that is vital to the heart's ability to pump blood effectively. These layers are: Epicardium Description : The outermost layer of the heart. Structure : It is a thin layer of connective tissue and epithelial cells that also forms part of the pericardium (the sac surrounding the heart). Function : The epicardium serves as a protective outer layer. It contains blood vessels, nerves, and lymphatics that supply the myocardium. It also acts as a lubricating surface to reduce friction between the heart and surrounding structures as the heart beats.

8. Myocardium Description : The middle, thickest, and most muscular layer of the heart. Structure : Composed mainly of cardiac muscle fibers ( myocytes ) arranged in a spiral or helical pattern that enables effective contraction. Function : It is responsible for the heart’s pumping action. The myocardial tissue contracts and relaxes in response to electrical signals, which allows the heart to pump blood through the circulatory system. The myocardium is the thickest in the left ventricle because it must pump blood throughout the entire body, whereas the myocardium in the right ventricle is thinner as it only pumps blood to the lungs.

9. Endocardium Description : The innermost layer of the heart. Structure : A thin, smooth membrane composed of endothelial cells (similar to the lining of blood vessels) and underlying connective tissue. Function : It lines the inner chambers of the heart, including the heart valves. It provides a smooth surface for blood to flow over, which helps prevent blood clots and reduces friction. The endocardium also plays a role in maintaining the electrical system of the heart, as it surrounds the heart’s conduction tissues.

10. Pumping Blood: Receiving deoxygenated blood from the body through the veins Pumping oxygenated blood from the lungs to the body through the arteries Maintaining blood pressure

11. Cardiac Cycle: Diastole: Relaxation and filling of heart chambers Systole: Contraction and pumping of blood

12. Heart Functions : Atrial Function: Receiving blood and pumping it to the ventricles Ventricular Function: Pumping blood to the lungs and body Sinoatrial (SA) Node Function: Regulating heartbeat rhythm4. Atrioventricular (AV) Node Function: Coordinating atrial and ventricular contractions

13. Blood Circulation: Pulmonary circulation: Heart to lungs and back Systemic circulation: Heart to body and back

14. Regulation of Blood Pressure : Heart rate regulation Stroke volume regulation Vasodilation and vasoconstriction

15. Other Functions: Hormone regulation (e.g., atrial natriuretic peptide) Electrocardiogram (ECG) generation Maintenance of blood pH levels

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