The Cardiovascular System: The Heart PDF

The Cardiovascular System The Heart Lec 3 Dr. Farah Talib  Heart Anatomy Approximately the size of your fist Location Superior surface of diaphragm Left of the midline Anterior to the vertebral column, posterior to the sternum.  Coverings...

The Cardiovascular System The Heart Lec 3 Dr. Farah Talib  Heart Anatomy Approximately the size of your fist Location Superior surface of diaphragm Left of the midline Anterior to the vertebral column, posterior to the sternum.  Coverings of the Heart: Anatomy Pericardium – a double-walled sac around the heart composed of: 1. A superficial fibrous pericardium 2. A deep two-layer serous pericardium The parietal layer lines the internal surface of the fibrous pericardium The visceral layer or epicardium lines the surface of the heart They are separated by the fluid-filled pericardial cavity The Function of the Pericardium: 1. Protects and anchors the heart 2. Prevents overfilling of the heart with blood 3. Allows for the heart to work in a relatively friction free environment  Heart Wall Epicardium – visceral layer of the serous pericardium Myocardium – cardiac muscle layer forming the bulk of the heart Fibrous skeleton of the heart, a layer of connective tissue Endocardium – endothelial layer of the inner surface of the heart. External Heart: Major Vessels of the Heart (Anterior View) Vessels returning blood to the heart include: 1. Superior and inferior venae cavae 2. Right and left pulmonary veins Vessels conveying blood away from the heart include: 1. Pulmonary trunk, which splits into right and left 2. pulmonary arteries 3. Ascending aorta  External Heart: Vessels that Supply/Drain the Heart (Anterior View) Arteries –mainly coronary arteries Veins – small cardiac, anterior cardiac, and great cardiac veins Atria of the Heart Atria are the receiving chambers of the heart Blood enters right atria from superior and inferior venae cava and coronary sinus Blood enters left atria from pulmonary veins Ventricles of the Heart Ventricles are the discharging chambers of the heart Right ventricle pumps blood into the pulmonary arteries Left ventricle pumps blood into the aorta Pathway of Blood Through the Heart and lungs Right atrium → tricuspid valve → right ventricle Right ventricle → pulmonary semilunar valve → pulmonary arteries → lungs Lungs → pulmonary veins → left atrium Left atrium → bicuspid valve → left ventricle Left ventricle → aortic semilunar valve → aorta Aorta → systemic circulation Coronary Circulation Coronary circulation is the functional blood supply to the heart muscle itself Heart Valves Heart valves ensure unidirectional blood flow through the heart 1. Atrioventricular (AV) valves lie between the atria and the ventricles AV valves prevent backflow into the atria when ventricles contract 2. Semilunar valves prevent backflow of blood into the ventricles 3. Aortic semilunar valve lies between the left ventricle and the aorta 4. Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk Heart Valves Heart Physiology: Sequence of Excitation Blood and lymphatic system Blood and lymph system Blood is a fluid consisting of formed elements and plasma. It is produced by bone marrow, and the volume depends on body weight. An individual weighing 154 pounds has a blood volume of about 5 quarts/liters. Function of blood It provides a means of transportation for: 1. Transporting respiratory gases… oxygen and carbon dioxide 2. Chemicals, such as those found in food, hormones, and salts 3. Cells that protect the body from foreign substances  The vascular tree is organized into a hierarchical network of arteries, arterioles, capillary beds, veins, and venules that span several orders of magnitude in diameter. All vessels are characterized by an inner layer of endothelium and an outer layer of basement membrane. Blood plasma Plasma (PLAZ mah) is the fluid part of the blood. It is clear or straw-colored. It comprises 55% of the total blood volume, and is mostly water and proteins. Lymph Lymph is the clear, nearly colorless, alkaline fluid that occupies the space between all cells of the body. The term for this is ‘interstitial fluid’ (in ter STISH awl), and it is similar to blood plasma. It is 95% water. It seeps in and out through the walls of very small vessels called capillaries. Lymph is mostly fluid from blood plasma. Lymphatic system The lymphatic system is connected to the circulatory system. It consists of capillaries, vessels, ducts, and nodes. This system transports lymph one- way…back to the blood stream. There is no pump, but the lymph moves via skeletal muscle action, respiratory movement, and contraction of smooth muscle in vessel walls. Lymph nodes Lymph nodes are filters, slowing down and cleaning the lymph before returning it to the blood. The dark lumps on the membrane are lymph nodes Accessory organs to the lymphatic system: 1. Spleen The spleen is a soft, dark purple organ found in the upper-left portion of the abdomen and surrounded by blood and lymph vessels. The red pulp of the spleen removes old red blood cells (erythrocytes) from the blood supply. The white pulp of the spleen removes, stores and produces white blood cells (lymphocytes). Accessory organs to the lymphatic system 2. Tonsils The tonsils are located in masses of tissue in the back of the throat. They filter bacteria and produce white blood cells. Tonsils are sometimes removed if they become so large they cause an obstruction or if they are chronically inflamed. Accessory organs to the lymphatic system 3. The thymus gland The thymus gland is usually considered as part of the endocrine system, but is actually part of the lymphatic system due to its appearance and function. It manufactures one specific type of the infection-fighting lymphocytes. They are aptly called T-cells. Do not confuse the thymus gland with the thyroid gland