Cardiovascular system
- 1. Cardiovascular system Subject: Human anatomy and physiology-I Unit-V Prepared by: Kajale Fulchand V. (M.Pharm Pharmacology) Assistant Professor Shivai Charitable trust’s College of Pharmacy.
- 2. Introduction • The scientific study of the normal heart and the diseases associated with it is known as cardiology • The heart is relatively small, roughly about 12cm (5 inches) long , 9cm (3.5 inches) wide at its broadest point , and 6cm (2.5 inches) thick, with an average mass of 250g in adult females and 300g in adult males. • The heart lies in the mediastinum an anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs • The pointed apex is formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. It is directed anteriorly, inferiorly, and to the left. • The base of the heart is opposite the apex and is its posterior aspect. It is formed by the atria (upper chambers) of the heart, mostly the left atrium
- 3. Anatomy of the Heart
- 4. Layers of the Heart Wall • The superficial fibrous Pericardium is composed of tough, inelastic, dense irregular connective tissue. • The middle Myocardium is responsible for the pumping action of the heart and is composed of cardiac muscle tissue. It makes up approximately 95% of the heart wall • The innermost Endocardium is a thin layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves of the heart.
- 6. Systemic and Pulmonary Circulations • In postnatal circulation, the heart pumps blood into two closed circuits with each beat systemic circulation and pulmonary circulation • As each chamber of the heart contracts, it pushes a volume of blood into a ventricle or out of the heart into an artery. Valves open and close in response to pressure changes as the heart contracts and relaxes. Each of the four valves helps ensure the one-way flow of blood by opening to let blood through and then closing to prevent its backflow. • The left side of the heart is the pump for systemic circulation; it receives bright red oxygenated (oxygen-rich) blood from the lungs. • The left ventricle ejects blood into the aorta. From the aorta, the blood divides into separate streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body except for the air sacs (alveoli) of the lungs, which are supplied by the pulmonary circulation. • In systemic tissues, arteries give rise to smaller-diameter arterioles, which finally lead into extensive beds of systemic capillaries. Exchange of nutrients and gases occurs across the thin capillary walls.
- 7. • Blood unloads O2 (oxygen) and picks up CO2(carbon dioxide). In most cases, blood flows through only one capillary and then enters a systemic venule. Venules carry deoxygenated (oxygen-poor) blood away from tissues and merge to form larger systemic veins. Ultimately the blood flows back to the right atrium. • The right side of the heart is the pump for pulmonary circulation; it receives all of the dark-red deoxygenated blood returning from the systemic circulation. • Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. In pulmonary capillaries, blood unloads CO2, which is exhaled, and picks up O2 from inhaled air. • The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium. • Blood pressure is the force or pressure that the blood exerts on the walls of blood vessels.
- 9. The Conduction System • Cardiac excitation normally begins in the sinoatrial (SA) node, located in the right atrial wall just inferior and lateral to the opening of the superior vena cava • By conducting along atrial muscle fibers, the action potential reaches the atrioventricular (AV) node, located in the interatrial septum, just anterior to the opening of the coronary sinus • From the AV node, the action potential enters the atrioventricular (AV) bundle. Also known as the bundle of His. • Aft er propagating through the AV bundle, the action potential enters both the right and left bundle branches. • Finally, the large-diameter Purkinje fibers rapidly conduct the action potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward the valves. • The SA node sets the rhythm for contraction of the heart. It is the natural pacemaker.
- 11. Cardiac cycle At rest, the healthy adult heart is likely to beat at a rate of 60–80 beats per minute (b.p.m.). During each heartbeat, or cardiac cycle, the heart contracts (systole) and then relaxes (diastole). Stages of the cardiac cycle • Atrial systole= contraction of the atria • Ventricular systole=contraction of the ventricles • Complete cardiac diastole= relaxation of the atria and ventricles
- 12. Autonomic Regulation of Heart Rate • Nervous system regulation of the heart originates in the cardiovascular (CV) center in the Medulla oblongata. • This region of the brain stem receives input from a variety of sensory receptors and from higher brain centers, such as the limbic system and cerebral cortex. • The cardiovascular center then directs appropriate output by increasing or decreasing the frequency of nerve impulses in both the sympathetic and parasympathetic branches of the ANS. • Chemical Regulation of Heart Rate 1. Hormones. Epinephrine and norepinephrine (from the adrenal medullae) enhance the heart’s pumping effectiveness. 2. Cations. intracellular and extracellular concentrations of several cations e.g. Na+ and K+ Cardiac output (CO) is the volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute.
- 13. • Baroreceptors (pressure receptors) • A rise in blood pressure in these arteries stimulates the baroreceptors, increasing their input to the CVC. The CVC responds by increasing parasympathetic nerve activity to the heart; this slows the heart down. • At the same time, sympathetic stimulation to the blood vessels is inhibited, causing vasodilation. The net result is a fall in systemic blood pressure. • Chemoreceptors • They sense changes in the levels of carbon dioxide, oxygen and the acidity of the blood (pH) . Rising blood CO2, falling blood O2 levels and/or falling arterial blood pH all indicate failing tissue perfusion. • When these changes are detected by the chemoreceptors, they send signals to the CVC, which then increases sympathetic drive to the heart and blood vessels, pushing blood pressure up to improve tissue blood supply.
- 14. • stroke volume (SV), the volume of blood ejected by the ventricle during each contraction.
- 16. o Electrocardiogram • The instrument used to record the changes is an electrocardiograph. • As action potentials propagate through the heart, they generate electrical currents that can be detected at the surface of the body. An electrocardiogram abbreviated either ECG or EKG (from the German word Elektrokardiogram), is a recording of these electrical signals
- 17. Heart sounds • Blood turbulence from closing valves • Lubb • Dupp • Pulse • The pulse can be felt with gentle finger pressure in a superficial artery when its wall is distended by blood pumped from the left ventricle during contraction (systole). • Disorders of heart • Atherosclerosis • Arrhythmias • Congestive Heart Failure
- 18. Reference 1. Anatomy and Physiology in Health and Illness by Kathleen J.W. Wilson, Churchill Livingstone, New York 2. Principles of Anatomy and Physiology by Tortora Grabowski. Palmetto, GA, U.S.A. 3. Essentials of Medical Physiology by K. Sembulingam and P. Sembulingam. Jaypee brothers medical publishers, New Delhi.