ANA 2 Anatomy and Physiology 2 PDF

ANA 2 Anatomy and Physiology 2 Mark Joseph V. Liwanag, MSN, RN Course facilitator MODULE 2- Unit IV Cardiovascular System: HEART  HEART HEART ▪ A muscular organ that pumps blood through the body ▪ Pumps approx. 5L/min of blood ▪ Approx. the si...

ANA 2 Anatomy and Physiology 2 Mark Joseph V. Liwanag, MSN, RN Course facilitator MODULE 2- Unit IV Cardiovascular System: HEART  HEART HEART ▪ A muscular organ that pumps blood through the body ▪ Pumps approx. 5L/min of blood ▪ Approx. the size of a closed fist Cardiovascular system – the heart + blood vessels + blood ▪ Pulmonary circulation – right side of the heart pumps blood to the lungs; then back to the left side ▪ Systemic circulation – left side of the heart pumps blood to all other tissues of the body; then back to the right side  FUNCTIONS 1. Generating blood pressure. Contractions of the heart generate blood pressure 2. Routing blood. separates the pulmonary and systemic circulations 3. Ensuring one-way blood flow. valves of the heart ensure a one-way flow of blood 4. Regulating blood supply. rate and force of heart contractions change to meet the metabolic needs of the tissues  Size, Shape, and Location of the Heart ▪ Apex – blunt, rounded point of the heart ▪ Base – larger, flat part at the opposite end of the heart ▪ Mediastinum – midline partition ▪ Pericardial cavity – surrounding cavity of the heart Importance of location and shape of the Heart ▪ To accurately place a stethoscope ▪ To place chest leads for ECG ▪ To administer CPR LOCATION OF THE HEART ▪ apex is also directed to the left, approximately two-thirds of the heart’s mass lies to the left of the midline of the sternum ▪ base of the heart is located deep to the sternum and extends to the level of the second intercostal space ▪ APEX is deep to the left fifth intercostal space, approximately 7–9 centimeters (cm) to the left of the sternum near the midclavicular line, which is a perpendicular line that extends down from the middle of the clavicle ANATOMY OF THE HEART: Pericardium ▪ Pericardial cavity – where the heart lies; is formed by the pericardium ▪ Pericardium/Pericardial sac – surrounds the heart and anchors it within the mediastinum ▪ Fibrous pericardium – tough, fibrous connective tissue outer layer ▪ Serous pericardium – inner layer consists of flat epithelial cells with a thin layer of connective tissue 1. Parietal pericardium –part lining the fibrous pericardium 2. Visceral pericardium/Epicardium – portion covering the heart surface ▪ Pericardial fluid – produced by the SP; reduces friction as the heart moves ANATOMY OF THE HEART: External Anatomy ▪ Atria – entrance chamber; at the base of the heart ▪ Ventricles – cavities; extend from the base of the heart to the apex SULCI/GROOVES – on the surface of the heart; contains blood vessels and fats ▪ Coronary sulcus – separates the atria from the ventricles ▪ Anterior interventricular sulcus - extends inferiorly from the coronary sulcus on the anterior surface of the heart ▪ Posterior interventricular sulcus - extends inferiorly from the coronary sulcus on the posterior surface of the heart  ANATOMY OF THE HEART: External Anatomy Six large veins carry blood to the atria of the heart 1. Superior & Inferior vena cava – carry blood to the RA 2. Pulmonary veins – carry blood from the lungs to the LA (four) Two arteries, often called the great vessels or great arteries carry blood away from the ventricles Pulmonary trunk & aorta – exit the heart 1. Pulmonary arteries – carry blood to the lungs 2. Aorta – carries blood to the rest of the body  Heart Chambers and Internal Anatomy A. Right and Left Atria ▪ Receives blood from the veins ▪ Function as reservoirs; where blood returning from veins collects before it enters the ventricles ▪ Interatrial septum – separator of the two atria right atrium receives blood from three major openings: 1. the superior vena cava, 2. the inferior vena cava, and 3. the coronary sinus. left atrium receives blood through the four pulmonary veins, which drain blood from the lungs.  Heart Chambers and Internal Anatomy B. RIGHT AND LEFT VENTRICLE ▪ Major pumping chambers ▪ Ejects blood into the arteries and forces it to flow through the CS ▪ INTERVENTRICULAR SEPTUM – separator of the two ventricles 1. right ventricle pumps blood into the pulmonary trunk 2. left ventricle pumps blood into the aorta. wall of the left ventricle is thicker than the wall of the right ventricle  HEART VALVES HEART VALVES – maintain one-way flow of blood through ▪ two types of heart valves: atrioventricular valves and semilunar valves. A. Atrioventricular valves ▪ Allows blood to flow from the atria into the ventricles; ▪ Prevents it from flowing back into the atria 1. Tricuspid valve – bet. the RA and the RV (three cusps) 2. Bicuspid/Mitral valve – bet. the LA and the LV two cusps  HEART VALVES B. SEMILUNAR VALVE is located between each ventricle and its associated great artery. 1. PULMONARY SEMILUNAR VALVE - is located between the right ventricle and the pulmonary trunk 2. AORTIC SEMILUNAR VALVE - is located between the left ventricle and aorta Each valve consists of three pocketlike semilunar (half-moon-shaped) cusps  HEART VALVES ▪ Papillary muscles – cone- shaped, muscular pillars; prevents the valves from opening into the atria ▪ Chordae tendineae – thin, strong, connective tissue strings  SUPPORTIVE STRUCTURE CARDIAC SKELETON, OR FIBROUS SKELETON ▪ A plate of connective tissue ▪ consists mainly of fibrous rings that surround the atrioventricular and semilunar valves and give them solid support ▪ serves as electrical insulation between the atria and the ventricles ▪ provides a rigid attachment site for cardiac muscle. Route of Blood Flow Through the Heart  BLOOD SUPPLY TO THE HEART ▪ Two CORONARY ARTERIES supply blood to the wall of the heart ▪ originate from the base of the aorta, just above the aortic semilunar valves. 1. LEFT CORONARY ARTERY - originates on the left side of the aorta Three major branches: A. ANTERIOR INTERVENTRICULAR ARTERY - lies in the anterior interventricular sulcus B. CIRCUMFLEX ARTERY - extends around the coronary sulcus on the left to the posterior surface of the heart C. LEFT MARGINAL ARTERY - extends inferiorly along the lateral wall of the left ventricle from the circumflex artery. ▪ supply much of the anterior wall of the heart and most of the left ventricle. BLOOD SUPPLY TO THE HEART 2. RIGHT CORONARY ARTERY originates on the right side of the aorta. It extends around the coronary sulcus on the right to the posterior surface of the heart A. POSTERIOR INTERVENTRICULAR ARTERY- which lies in the posterior interventricular sulcus. B. RIGHT MARGINAL ARTERY - extends inferiorly along the lateral wall of the right ventricle. right coronary artery and its branches supply most of the wall of the right ventricle.  BLOOD SUPPLY TO THE HEART CORONARY CIRCULATION also includes veins that carry the blood from the heart walls to the right atrium. Two major veins draining the blood from the heart wall tissue: 1. GREAT CARDIAC VEIN - drains blood from the left side of the heart 2. SMALL CARDIAC VEIN - drains the right margin of the heart ▪ most of them drain blood into the coronary sinus CORONARY SINUS - a large vein located within the coronary sulcus on the posterior aspect of the heart. ▪ Blood flows from the coronary sinus into the right atrium HISTOLOGY OF THE HEART: Heart Wall 1. Epicardium/Visceral pericardium ▪ Thin, serous membrane forming the smooth outer surface ▪ Consists of simple squamous epithelium overlaying a layer of loose connective tissue + adipose tissue 2. Myocardium ▪ Composed of cardiac muscles ▪ Responsible for contraction of the heart chambers HISTOLOGY OF THE HEART: Heart Wall 3. ENDOCARDIUM ▪ Simple squamous epithelium over a layer of connective tissue ▪ Allows blood to move easily ▪ Forms the heart valves Trabeculae carneae – ridges and columns of cardiac muscle HISTOLOGY OF THE HEART: Cardiac Muscle CARDIAC MUSCLE CELLS ▪ Elongated, branching cells ▪ Two, centrally located nuclei ▪ Contains actin and myosin myofilaments that form sarcomeres ▪ Rich in mitochondria (produce ATP at rapid rate) ▪ Relies on Ca2 + and ATP for contraction ▪ Actin & Myosin myofilaments – responsible for muscle contraction HISTOLOGY OF THE HEART: Cardiac Muscle ▪ Organization of A&M myofilaments – gives the cardiac muscle a striated (banded) appearance ▪ Intercalated disks – specialized cell-to-cell contacts; greatly increase contact in between; prevents cells from pulling apart ▪ Gap junctions – specialized cell membrane structures; allow cytoplasm to flow freely bet. cells ELECTRICAL ACTIVITY OF THE HEART Action Potentials in Cardiac Muscle 1. Depolarization phase 2. Plateau phase – period of slow repolarization 3. Repolarization phase – achieves its maximum degree of polarization; returns to the resting membrane potential REFRACTORY PERIOD ▪ Allows cardiac muscle to contract and relax almost completely before another action potential can be produced action potentials in cardiac muscle are ▪ Prevents tetanic contractions from different from those in skeletal muscle because the plateau phase makes the action occurring potential and its refractory period last longer.  Conduction System of the Heart Specialized cardiac muscle cells in the heart wall ▪ Sinoatrial node (SA) – heart’s pacemaker; initiates the contraction of the heart ▪ Atrioventricular node (AV) – spreads action potential slowly ▪ Atrioventricular bundle – a bundle of specialized cardiac muscle  Conduction System of the Heart ▪ Left & Right bundle branches – two branches of conducting tissue ▪ Purkinje fibers – conduct action potentials more rapidly than do other cardiac muscle fibers  Conduction System of the Heart 1. Action potentials originate in the sinoatrial (SA) node and travel across the wall of the atrium (arrows) from the SA node to the atrioventricular (AV) node. 2. Action potentials pass through the AV node and along the atrioventricular (AV) bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum.  Conduction System of the Heart 3. The AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches. 4. Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls.  Electrocardiogram (ECG) ELECTROCARDIOGRAM (ECG) An extremely valuable tool for diagnosing a number of cardiac abnormalities ▪ P wave – depolarization of the atrial myocardium ▪ QRS complex – depolarization of the ventricles ▪ T wave – repolarization of ventricles  Electrocardiogram (ECG) ▪ PQ interval – time bet. the beginning of the P wave and the beginning of the QRS complex; atria contracts and begins to relax ▪ PR interval – common name because the Q wave is very small ▪ QT interval – represents the time req. for ventricular depolarization and repolarization ECG is a record of electrical events of the heart and is not a direct measurement of mechanical events Electrocardiogram (ECG)  Abnormal Heart Rhythms ▪ Tachycardia - Heart rate in excess of 100 beats per minute (bpm) ▪ Bradycardia - Heart rate less than 60 bpm  CARDIAC CYCLE Repetitive pumping process of cardiac muscle contractions Major events: 1. Atrial systole 2. Ventricular contraction 3. Ejection 4. Ventricular relaxation 5. Passive ventricular filling ▪ Atrium – primer pump; complete the filling of ventricles with blood ▪ Ventricle – power pump; produce the major force that causes blood to flow  CARDIAC CYCLE ▪ Atrial systole – contraction of two atria ▪ Ventricular systole – contraction of two ventricles ▪ Atrial diastole – relaxation of the two atria ▪ Ventricular diastole – relaxation of the two ventricles  HEART SOUNDS ▪ Stethoscope – used to listen to the sounds of the lungs and the heart ▪ Lubb – closure of the AV valves ▪ Dupp – closure of the semilunar valves ▪ Murmurs – abnormal heart sounds; result of a faulty valve ▪ Stenosed – when opening of a valve is narrowed; swishing sound precedes  Regulation of Heart Function Various measurements can be taken to assess the heart’s function. ▪ Cardiac output (CO) – vol. of blood pumped by the heart; 5 L/min ▪ Stroke volume (SV) – vol. of blood pumped per ventricle per contraction; 70 mL/beat ▪ Heart rate (HR) – no. of times the heart contracts per minute; 72 beats/min CO = SV x HR  Intrinsic Regulation of the Heart Mechanisms contained within the heart itself ▪ VENOUS RETURN – amt. of blood that returns to the heart ▪ Preload – degree to which the ventricular walls are stretched at the end of diastole ▪ Starling’s Law of the Heart – relationship bet. preload and stroke volume ▪ Afterload – pressure against which the ventricles must pump blood  Extrinsic Regulation of the Heart Mechanisms external to the heart A. NERVOUS REGULATION: ▪ Baroreceptor Reflex - A mechanism of the nervous system in regulating heart function ▪ Baroreceptors – stretch receptors that monitor blood pressure ▪ Cardioregulatory center – receives and integrates action potentials form the baroreceptors  Extrinsic Regulation of the Heart B. CHEMICAL REGULATION: Chemoreceptor Reflex - ▪ Epinephrine & Norepinephrine – causes increased HR and SV ▪ Increase CO2 - increase sympathetic stimulation of the heart, resulting in increased heart rate and force of contraction Representative Diseases and Disorders of the Heart ▪ Coronary heart disease - Reduces the amount of blood the coronary arteries can deliver to the myocardium ▪ Coronary thrombosis - Formation of blood clot in a coronary artery ▪ Myocardial infarction - Damaged cardiac muscle tissue resulting from lack of blood flow to the myocardium; often referred to as a heart attack. Representative Diseases and Disorders of the Heart ▪ Endocarditis - Inflammation of the endocardium; affects the valves more severely than other areas of the endocardium ▪ Pericarditis - Inflammation of the pericardium ▪ Rheumatic heart disease - Results from a streptococcal infection in young people; infection that can result in rheumatic endocarditis Representative Diseases and Disorders of the Heart ▪ SEPTAL DEFECT - Hole in the septum between the left and right sides of the heart, allowing blood to flow from one side of the heart to the other. ▪ CYANOSIS - Symptom of inadequate heart function in babies with congenital heart disease ▪ the infant’s skin appears blue because of low oxygen levels in the blood in peripheral blood vessels  REFERENCES: VanPutte C. et.al. (2019). Seeley’s Essentials of Anatomy & Physiology. 10th edition. New York: McGraw Hill Co. Inc.