Lesson 1 Chapter 21 – The Cardiovascular System

Lesson 1 Chapter 21 – The Cardiovascular System 1 Unit 8 Study Guide The Heart The heart essentially functions as a pump, moving deoxygenated blood to the lungs, and oxygenated blood into systemic circulation. Essential to understanding cardiac anatomy, understands the mechanical (pumping) function of the heart, as well as the blood supply to the heart itself, and finally the conduction system driving the heart. Orientation of the Heart The heart is located in the chest between the lungs behind the sternum and above the diaphragm. It is surrounded by the pericardium. Its size is about that of a fist, and its weight is about 250-300 g. Its center is located about 1.5 cm to the left of the midsagittal plane. Located above the heart are the great vessels: the superior and inferior vena cava, the pulmonary artery and vein, as well as the aorta. The aortic arch lies behind the heart. The esophagus and the spine lie further behind the heart. Has 4 borders: superior, inferior, right and left • Heart sits at oblique angle and is slightly rotated to the left, so: Base forms superior border (aka superior surface) RA forms right border LV and LA form left border RV forms inferior border (aka inferior surface) • Heart also has anterior (sternocostal) surface and posterior (diaphragmatic) surface Lesson 1 Chapter 21 – The Cardiovascular System BASE is the superior part of the heart (where all of the vessels are attached) [Top of heart] APEX is the tip of the heart forming the corner of the inferior border and left border of the heart. Located usually in the 5th intercostal space in the mid-clavicular line. [Bottom of heart] The Pericardium The pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava, and the pulmonary artery. It has several functions: - Keep the heart contained in the chest cavity. Prevents the heart from over expanding when blood volume increases. Limits heart motion. The pericardium is divided into three layers:    Fibrous Pericardium - the outer fibrous sac that covers the heart. Parietal Pericardium - lies between the visceral pericardium and the fibrous pericardium. Visceral Pericardium - also called the epicardium, this is the outer layer of the wall of the heart. Pericardial Cavity The pericardial cavity lies between the visceral pericardium and the parietal pericardium. This cavity is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes. 2 Lesson 1 Chapter 21 – The Cardiovascular System 3 The Heart Wall Layers of the Heart 1. Epicardium – external surface of the heart (this is the visceral pericardium) 2. Myocardium – cardiac muscle, connective tissue (including a fibrous skeleton), nerves. 3. Endocardium – epithelium lining inner surface of the heart, including the valves Internal Anatomy The heart has 4 chambers: 1) Right Atrium (RA) a. Receives deoxygenated (used) venous blood from systemic circulation (via superior and inferior vena cava) and coronary vessels (coronary sinus) b. Interatrial septum separates the RA from the LA. c. Blood from the RA crosses the tricuspid (3 cusp) valve and into the RV 2) Right Ventricle (RV) a. Deoxygenated blood from the RA enters the RV across the tricuspid valve (aka right atrioventricular valve) b. The 3 cusps are attached to collagen fiber branches called chordae tendinae which arise from papillary muscles within the RV. c. Blood leaves the RV across the pulmonary valve and into the pulmonary arteries. Lesson 1 Chapter 21 – The Cardiovascular System 4 3) Left Atrium (LA) a. Receives oxygenated blood from pulmonary veins b. Interatrial septum separates the RA from the LA. c. Blood travels from the LA across the mitral (bicuspid – two cusps, aka left atrioventricular) valve into the LV. 4) Left Ventricle (LV) a. Receives oxygenated blood from the LA b. The chordae tendinae of the mitral valve are attached to papillary muscles in the LV c. Pumps oxygenated blood across the aortic valve (also a semilunar valve) into the ascending aorta to the systemic arterial system and into the coronary arteries via the coronary sinuses (located in the base of the ascending aorta) d. The muscular wall surrounding the LV is thicker than any other chamber because it needs to pump blood throughout the entire body. Lesson 1 Chapter 21 – The Cardiovascular System 5 Conditions Hole in the heart = ASD (Atrial Septal Defect) Cannot open widely (valves) = stenosis Cannot close properly/tightly (valves) = incompetence Valves of the Heart Atrioventricular Valves (AV valves) The atrioventricular valves are thin structures that are composed of endocardium and connective tissue. They are located between the atria and the ventricles. [Mitral valve and tricuspid valve] – Right AV valve (tricuspid) – between RA and RV – Left AV valve (bicuspid or mitral) – between LA and LV Semilunar Valves The semilunar valves are flaps of endocardium and connective tissue reinforced by fibers which prevent the valves from turning inside out. They are shaped like a half moon, hence the name semilunar (semi-, -lunar). [Aortic Valve and Pulmonary valve] – Pulmonary semilunar valve (leaves RV) – Aortic semilunar valve (leaves LV) The heart functions as two pumps that work simultaneously • • The right side of the heart receives deoxygenated (used) blood and pumps it to the lungs to be oxygenated The left side of the heart receives oxygenated blood and pumps it to the entire body as well as the coronary arteries Lesson 1 Chapter 21 – The Cardiovascular System 6 Coronary Arteries The coronary arteries are the first blood vessels that branch off from the ascending aorta. The aorta is the largest artery in the body. It transports and distributes oxygen rich blood to all arteries. The coronary arteries extend from the aorta to the heart walls supplying blood to the atria, ventricles, and septum of the heart. – Originate within the aortic sinus at the base of the ascending aorta (pressure here is enormous to ensure blood supply to the heart) – Two major coronary arteries: • Right coronary artery – branches out to supply oxygenated blood to RA, RV, part of LA, part of LV, interatrial septum, part of interventricular septum and part of the conducting system of heart • Left coronary artery - branches out to supply oxygenated blood to LA, LV, parts of RV, parts of interventricular septum Lesson 1 Chapter 21 – The Cardiovascular System 7 • Cardiac Veins – Collects wastes from cardiac muscle – Drains deoxygenated blood into the coronary sinus (large vein) on posterior surface of heart – Coronary sinus empties into RA Conduction System of the Heart • Cardiac muscle tissue contracts in response to electrical impulses originating within the muscle tissue itself (unlike skeletal muscle) • This ability to generate and conduct its own impulses is called autorhythmicity or automaticity • So, there is a lot going on in the heart: • Electrical activity (which initiates contraction) • Mechanical activity (pumping) • Coronary blood supply (taking care of its own needs too) Heart block – a disconnect between connection systems ex. SA node and AV node Can cause bradycardia or arrhythmias (irregular heart beat) [SA/AV] 1. SA (sinoatrial) node – this is the main pacemaker of the heart…it originates the electrical impulse. SA node is located in the posterior wall of the right atrium. 2. The impulse initiated by the SA node travels down through conducting fibers to the AV (atrioventricular) node. AV node is in the floor of the right atrium. As the impulse travels down the internodal pathways, it also travels outward through the cardiac muscle, starting atrial contraction. Lesson 1 Chapter 21 – The Cardiovascular System 8 3. From the AV node, the impulse travels to the AV bundle (aka the Bundle of His) – a bundle of conducting fibers 4. The AV bundle travels a short way down the interventricular septum before dividing into the right bundle branch (RBB) and left bundle branch (LBB) and travels on toward the apex of the heart 5. The bundle branches branch further into Purkinje fibers which travel through the ventricular myocardium As the impulse travels down the conducting fibers it also travels outward through the ventricular myocardium, starting ventricular contraction. Lesson 1 Chapter 21 – The Cardiovascular System Study the diagram 9 Lesson 1 Chapter 21 – The Cardiovascular System 10 Coronary Arteries: Branches Some of the arteries that extend from the main coronary arteries include:  Right Coronary Artery - Supplies oxygenated blood to the walls of the ventricles and the right atrium. o  Posterior Descending Artery - Supplies oxygenated blood to the inferior wall of the left ventricle and the inferior portion of the septum. Left Main Coronary Artery - Directs oxygenated blood to the left anterior descending artery and the left circumflex. o Left Anterior Descending Artery - Supplies oxygenated blood to the anterior portion of the septum as well as to the walls of the ventricles and the left atrium (front region of the heart). o Left Circumflex Artery - Supplies oxygenated blood to the walls of the ventricles and the left atrium (back region of the heart). Lesson 1 Chapter 21 – The Cardiovascular System 11 RIGHT ATRIUM (RA) LEFT ATRIUM (LA) - Receives deoxygenated venous blood from superior&inferior vena cava and coronary vessels (coronary sinus) - Superior delivers blood from the upper part (head, neck, upper limbs, chest) while inferior delivers blood from the lower part of the body (abdomen & pelvic cavities, lower limbs) - Interatrial septum separates the RA&LA - Blood from the triscupid valve (right atrioventricular (AV) valve) crosses from the RA to the RV - Receives oxygenated blood from the pulmonary veins - Interatrial septum separates the atriums - Blood travels from the LA across the mitral/ bicuspid valve (left atrioventricular valve) into the LV RIGHT VENTRICLE (RV) LEFT VENTRICLE (LV) - Deoxygenated blood from the RA enters the RV via the tricuspid valve (right atrioventricular valve) - 3 cusp (flaps) are attached to collagen fiber branches called cordae tendinae which arise from papillary muscles within the RV; these cordae tendinae prevent backflow of blood - Interventricular septum separates the RV&LV - Blood leaves the RV across the pulmonary semilunar valve  pulmonary trunk  left & right pulmonary arteries(deoxygenated)  lungs  pulmonary veins(oxygenated)  LA [pulmonary circulation] - Receives oxygenated blood from the LA via mitral/bicuspid valve(left atrioventricular valve) - Blood leaves the LV by passing through the aortic valve (aortic semilunar valve/semilunar valve) into the ascending aorta. - From aorta  systemic arterial system  Coronary arteries via coronary sinuses - Muscular wall surround the LV is thicker than any other chamber b/c it needs to pump blood throughout the entire body - Compared to RV, DOES NOT have a moderator band