lecture 1[Introduction to CVS] DPT.pptx

Introduction to Cardiovascular System Iqra shahzaib Lecturer, RIU  Cardiovascular System Includes heart and blood vessels. Heart pumps blood into the blood vessels. Blood vessels circulate the blood throughout the body. Blood transports nutrients and oxygen to the tis...

Introduction to Cardiovascular System Iqra shahzaib Lecturer, RIU  Cardiovascular System Includes heart and blood vessels. Heart pumps blood into the blood vessels. Blood vessels circulate the blood throughout the body. Blood transports nutrients and oxygen to the tissues and removes carbon dioxide and waste products from the tissues  Heart Muscular organ that pumps blood throughout the circulatory system. Situated in between two lungs Four chambers, two atria and two ventricles. Musculature of ventricles is thicker than that of atria. Force of contraction of heart depends upon the muscles.  Right Side Of The Heart Has two chambers – Right atrium – Right ventricle Right atrium is a thin walled and low pressure chamber. It has got the pacemaker known as sinoatrial node that produces cardiac impulses and atrioventricular node that conducts the impulses to the ventricles.  Right atrium receives venous (deoxygenated) blood via two large veins: – Superior vena cava that returns venous blood from the head, neck and upper limbs – Inferior vena cava that returns venous blood from lower parts of the body  Right atrium communicates with right ventricle through tricuspid valve. Wall of right ventricle is thick. Venous blood from the right atrium enters the right ventricle through this valve. From the right ventricle, pulmonary artery arises. It carries the venous blood from right ventricle to lungs. In the lungs, the deoxygenated blood is oxygenated.  Left Side Of The Heart Two chambers – Left Atrium – Left Ventricle Left atrium is a thin walled and low pressure chamber. It receives oxygenated blood from the lungs through pulmonary veins. Blood from left atrium enters the left ventricle through mitral valve (bicuspid valve).  Wall of the left ventricle is very thick. Left ventricle pumps the arterial blood to different parts of the body through systemic aorta.  Septa Of The Heart Right and left atria are separated from one another by a fibrous septum called inter atrial septum. Right and left ventricles are separated from one another by inter ventricular septum. Layers Of Wall Of The Heart Heart is made up of three layers of tissues: 1. Outer pericardium 2. Middle myocardium 3. Inner endocardium.  Pericardium Outer covering of the heart Made up of two layers: – Outer parietal pericardium – Inner visceral pericardium. The space between the two layers is called pericardial cavity or pericardial space and it contains a thin film of fluid.  Outer Parietal Pericardium – Forms a strong protective sac for the heart. – Helps also to anchor the heart within the mediastinum. – Parietal pericardium is made up two layers: Outer fibrous layer Inner serous layer  Inner Visceral Pericardium – Inner visceral pericardium lines the surface of myocardium. – It is made up of flattened epithelial cells. – Also known as epicardium  Myocardium – Middle layer of wall of the heart and it is formed by cardiac muscle fibers or cardiac myocytes. – Forms the bulk of the heart and it is responsible for pumping action of the heart. – Unlike skeletal muscle fibers, the cardiac muscle fibers are involuntary in nature. – Myocardium has three types of muscle fibers: 1. Muscle fibers which form contractile unit of heart 2. Muscle fibers which form pacemaker 3. Muscle fibers which form conductive system.  Endocardium Inner most layer of heart wall. Thin, smooth and glistening membrane. It is formed by a single layer of endothelial cells, lining the inner surface of the heart. Endocardium continues as endothelium of the blood vessels  Valves Of The Heart Four valves in human heart. Two valves are in between atria and the ventricles called atrioventricular valves. Two are the semilunar valves, placed at the opening of blood vessels arising from ventricles, namely systemic aorta and pulmonary artery. Valves of the heart permit the flow of blood through heart in only one direction.  Atrioventricular Valves Left atrioventricular valve known as mitral valve or bicuspid valve. It is formed by two valvular cusps or flaps. Right atrioventricular valve is known as tricuspid valve and it is formed by three cusps. Brim of the atrioventricular valves is attached to atrioventricular ring, which is the fibrous connection between the atria and ventricles. Cusps of the valves are attached to papillary muscles by means of chordae tendineae.  Papillary muscles arise from inner surface of the ventricles Papillary muscles play an important role in closure of the cusps and in preventing the back flow of blood from ventricle to atria during ventricular contraction. Atrioventricular valves open only towards ventricles and prevent the backflow of blood into atria.  Semilunar Valves Semilunar valves are present at the openings of systemic aorta and pulmonary artery and are known as aortic valve and pulmonary valve respectively. Made up of three flaps. Semilular valves open only towards the aorta and pulmonary artery and prevent the backflow of blood into the ventricles.  Actions Of The Heart Actions of the heart are classified into four types: 1. Chronotropic action 2. Inotropic action 3. Dromotropic action 4. Bathmotropic action. 1. Chronotropic Action – Chronotropic action is the frequency of heartbeat or heart rate. – It is of two types: Tachycardia or increase in heart rate Bradycardia or decrease in heart rate 2. Inotropic Action – Force of contraction of heart is called inotropic action. – It is of two types: Positive inotropic action or increase in the force of contraction Negative inotropic action or decrease in the force of contraction. 3. Dromotropic Action – Dromotropic action is the conduction of impulse through heart. – It is of two types: Positive dromotropic action or increase in the velocity of conduction Negative dromotropic action or decrease in the velocity of conduction. 4. Bathmotropic Action – Bathmotropic action is the excitability of cardiac muscle. – It is also of two types: Positive bathmotropic action or increase in the excitability of cardiac muscle Negative bathmotropic action or decrease in the excitability of cardiac muscle.  Blood Vessels Vessels of circulatory system are the aorta, arteries, arterioles, capillaries, venules, veins and venae cavae.  Arterial System Comprises the aorta, arteries and arterioles. Walls of the aorta and arteries are formed by three layers: 1. Outer tunica adventitia, which is made up of connective tissue layer. It is the continuation of fibrous layer of parietal pericardium. 2. Middle tunica media, which is formed by smooth muscles 3. Inner tunica intima, which is made up of endothelium. It is the continuation of endocardium.  Aorta, arteries and arterioles have two laminae of elastic tissues: – External elastic lamina between tunica adventitia and tunica media – Internal elastic lamina between tunica media and tunica intima.  Arterial branches become narrower and their walls become thinner while reaching the periphery. Aorta has got the maximum diameter of about 25 mm. Diameter; gradually decreased and at the end arteries, it is about 4 mm. It further decreases to 30 μ in the arterioles and ends up with 10 μ in the terminal arterioles. Resistance (peripheral resistance) is offered to blood flow in the arterioles and so these vessels are called resistant vessels. Pressure Changes Inside Blood Vessels  Venous System From the capillaries, venous system starts and it includes venules, veins and venae cavae. Capillaries end in venules, which are the smaller vessels with thin muscular wall than the arterioles. Diameter of the venules is about 20 μ. At a time, a large quantity of blood is held in venules and hence the venules are called capacitance vessels. Venules are continued as veins, which have the diameter of 5 mm. Veins form superior and inferior venae cavae, which have a diameter of about 30 mm.