Cardiovascular System.pdf

Second Lecture Zheer Mohammed Aziz  Learning Objectives ▪ General information on the heart Including chambers, pericardial sac, myocardium, valves, innervation and blood supply ▪ Cardiovascular physiology Including cardiac cycle, Heart sound, Heart waves, ECG ▪ Pathology of the He...

Second Lecture Zheer Mohammed Aziz  Learning Objectives ▪ General information on the heart Including chambers, pericardial sac, myocardium, valves, innervation and blood supply ▪ Cardiovascular physiology Including cardiac cycle, Heart sound, Heart waves, ECG ▪ Pathology of the Heart ▪ Clinical notes and Examination  The Heart ❑ The heart is a muscular organ enclosed in a fibrous sac ( The Pericardium ). ❑ The pericardial sac contains watery fluid that acts as a lubricant as the heart moves within the sac. ❑ The wall of the heart is composed of cardiac muscle cells, termed the myocardium. ❑ The inner surface of the wall is lined by a thin layer of endothelial cell, the endothelium.  The Heart ▪ The heart is actually two separate pumps : a right heart which pumps blood through the pulmonary artery into the lung, and a left heart which pumps blood through the aorta into the peripheral organ. ▪ Each of these two pumps is consists of two chambers, an atrium and a ventricle. ▪ Blood exists from the right ventricle through the pulmonary valve to the pulmonary trunk, and from the left ventricle through the aortic valve into the aorta.  The Heart The heart is divided by vertical septa into 4 chambers – The atrial (interatrial) septum into the right and left atria – The ventricular (interventricular) septum into the right and left ventricles – Its position is indicated on the surface of the heart by the anterior and posterior interventricular grooves  Pericardium Pericardium : A tough fibrinous sac which is shaped like a cone with an apex directed superiorly and a wide base inferiorly. Encloses the heart and the roots of the great vessels Lies within the middle mediastinum The base firmly attached below to the diaphragm. The apex fuses with the outer coats of the great blood vessels.  Pericardium Anteriorly :the pericardium is attached in front to the sternum Posteriorly: the pericardium is related to the bronchi, the descending esophagus. This aspect is pierced by four pulmonary veins. Layers of Pericardium 1-Fibrous pericardium, Its a dense irregular CT. 2- Serous pericardium: lines the fibrous pericardium and coatsthe heart, divided into:  Pericardium A-Parietal layer, lines the internal surface of the fibrous pericardium. B- Visceral layer, lines the surface of the heart. Pericardial cavity : is the slit like space between the parietal and visceral layers normally, contains a small amount of tissue fluid Called pericardial fluid, which acts as a lubricant to facilitate movements of the heart. Functions of the pericardium: Protect and fixes the heart in the mediastinum  Heart Physiologic anatomy of Cardiac Muscle : The heart is composed of three major types of cardiac muscle. 1- The atrial muscle. 2- The ventricular muscle 3- Specialized excitatory and conductive muscle fibers; an excitatory system of the heart that helps spread of the impulse (action potential) rapidly throughout the heart.  Heart Cardiac muscle cells (myocytes) are striated as they have typical myofibrils containing thin actin and thick myosin filaments, similar to those found in skeletal muscle, which slide along each other during the process of contraction. Unlike skeletal muscle (no gap junction), adjacent myocardial cells are joined end to end at structures called intercalated discs, there are electrical synapses or gap junctions, these gap junctions are protein channels that allow ions to flow from the cytoplasm of one cell directly into the next cell and, therefore action potentials  Heart That is, when one of these cells becomes excited, the action potential spreads rapidly throughout the intercalated discs and gap junctions to stimulate the neighbor cell, so the myocardium act almost as if it is a single cell; a syncytium, i.e., the cardiac muscle contracts or behaves as a single functional unit (syncytium property). Innervations of the heart The heart receives a rich supply of sympathetic and parasympathetic nerve fibers. The parasympathetic contained in (the vagus) nerves release acetylcholine. The sympathetic postganglionic fibers release norepinephrine (noradrenaline) The circulating epinephrine hormone from adrenal medulla also combines with the same receptors  The function of the heart valves The atrioventricular valves (AV valves) ▪ The tricuspid valve; the right AV valve, are composed of thin membranous which consists of three cusps, located cusps. After atrial contraction and just between right atrium and right before ventricular contraction, the AV ventricle. The function of AV valves is to valves begin to close and the (cusps) prevent backflow of blood into the atria come together by mean of backflow of the blood in the ventricles towards during ventricularcontraction. the atria. The AV valves include: ▪ Normally they allow blood to flow from the atrium to the ventricle but prevent The mitral valve; the left AV valve; backward flow from the ventricle to the bicuspid valve, which consists of two cusps located between leftatrium and atria. The atrioventricular valves contain left ventricle. and supported by (papillary muscles.)  Heart Valves ▪The aortic and pulmonary valves each consist of three semilunar cusps. ▪They contain no papillary muscle. ▪During diastole the cusps of these valves become closely approximated to prevent regurgitation of blood from aorta and pulmonary arteries into the ventricles. ▪*All valves close and open passively. ▪*There are no valves at entrance of superior, inferior vena cava and pulmonary veins into the atria.  Heart Valves What prevents the backflow of blood ? However little blood is ejected back into veins, this represents the venous pulse seen in the neck veins (jugular veins) when the atria contracting The pulmonary and systemic circulation Blood whose oxygen content has become partially depleted and carbon dioxide content has increased as a result of tissue metabolism returns to the right atrium. This blood then enters the ventricle, which pumps it into the pulmonary trunk and pulmonary arteries. ▪ The pulmonary arteries branch to transport blood to the lungs, where gas exchange occurs between the lung capillaries and the alveoli of the lungs. ▪ Oxygen diffuses from the air to the capillary blood; while carbon dioxide diffuses in the opposite direction. ▪ The blood that returns to the left atrium by way of the pul¬monary veins is therefore enriched in oxygen and partially de¬pleted of carbon dioxide. ▪ The blood that is ejected from the right ventricle to the lungs and back to the left atrium completes one circuit: called the pulmonary circulation.  Blood Circulation ▪Oxygen-rich blood in the left atrium enters the left ventricle and is pumped into a very large, elastic artery; the aorta. ▪The aorta ascends for a short distance, makes a U-turn, and then descends through the thoracic and abdominal cavities. ▪Arterial branches from the aorta supply oxygen-rich blood to all of the organ systems and are thus part of the systemic circulation. ▪As a result of cellular respiration, the oxygen concentration is lower and the carbon dioxide concentration is higher in the tissues than in the capillary blood.  Systemic Circulatory Blood that drains into the systemic veins is thus partially depleted of oxygen and increased in carbon dioxide content. These veins empty into two large veins; the superior and inferior venae cava that return the oxygen-poor blood to the right atrium. This completes the systemic circulation; from the heart (left ventricle), through the organ systems, and back to the heart (right atrium). Conductive System of the Heart Specialized excitatory and conductive system of the heart consists of : 1. Sinus node "SA" node: also called sinoatrial node, located in the right atrium. It is concerned with the generation of rhythmical impulse; it is the pacemaker of the heart that initiates each heart beat. This automatic nature of the heart beat is referred to as automaticity. 2. Internodal pathways conduct the impulse generated in SA node to the AV node. 3. The AV node (atrioventricular node), located near the right AV valve at the lower end of the interatrial septum, in the posterior septal wall of the right atrium. At which impulse from the atria is delayed before passing into the ventricles. Conductive System of the Heart 4. The AV bundle (bundle of His) conducts the impulse from the atria into ventricles. 5. The left and right bundles of purkinje fibers, which conduct the cardiac impulse to all parts of the ventricles. The purkinje fibers distribute the electrical excitation to the myocytes of the ventricles. Cardiovascular Physiology Physiological Properties of the Heart : 1) Automatic (autonomic) function. 2) Conductivity. 4) Contractility. 3) Excitability. 5) Rhythmicity. Cardiovascular Physiology 1) Automatic Function = ability to work also after an isolation Principle - existence of primary center of automatic function – the sino-atrial node – special excitatory system of the heart. 2) Conductivity The special conductive system of the heart. 3)Excitability Ability to react to stimulus. 4)The contractility Ability of the myocardial fibers to contract. 5) The Rhythmicity = regular alternation of contraction and relaxation Cardiovascular Physiology ▪All or Nothing Principle of the Heart = stimulation of any single atrial muscle fiber causes the action potential in entire atrial muscle mass. The same in ventricles. ▪Syncytial nature of cardiac muscle. Frank-Starling's law of the heart : that the force of myocardial contraction is directly proportional to the initial length of the cardiac muscle fibre This means that the greater the degree of stretching of the myocardium before contraction, the greater the force of contraction. The Significance of Frank-Starling's law The Starling's law allows autoregulation of myocardial contractility. Heart Sounds Heart Sounds : When the stethoscope is placed on the chest wall over the heart, two sounds are normally heard during each cardiac cycle (1st & 2nd heart sounds). Heart sounds are associated with closure of the valves with their associated vibration of the flaps of the valves. That is, heart sound does not produced by the opening of the valve because this opening is a slow developing process that makes no noise. Heart Sounds 1-The first heart sound (S1): is caused by closure of the AV valves when ventricles contract at systole. The vibration is soft, low- pitched lub. 2-The second heart sound (S2): is caused by closure of the aortic and pulmonary valves in the diastole. The vibration is loud, high- pitched dup. It is rapid sound because these valves close rapidly and continue for only a short period i.e., rapid, short and of higher pitch dub. Heart Sounds 3-The third heart sound (S3): is caused by rapid filling of the ventricles, it occurs after S2 / It is heard in normal heart; in children and in adult during exercise. 4-The fourth heart sound (S4): it is an atrial sound when the atria contract (at late diastole). It is a vibration sound (similar to that of S3). If present, it is heard before S1. (S4, S1,S2, S3). ECG What is an ECG ? An electrocardiogram or ECG, records electrical activity in the heart. An ECG machine records these electrical signals across multiple heart beats and produces an ECG strip. Heart Rate What are normal adult heart rates : Normal = 60 – 100 bpm Tachycardia > 100 bpm Bradycardia < 60 bpm What are the components : It is waveform components that consist of the electrical events during one heartbeat. Waveforms P wave : P wave is the first short upward movement of the ECG tracing. It indicates that the atria are contracting, pumping blood into the ventricles. Amplitude: 2-3 mm high The P-wave should be 2–3 small squares in duration Duration: 0.06 - 0.12 sec QRS complex Waveforms The QRS complex, normally beginning with a downward deflection, Q; a larger upwards deflection, a peak (R); and then a downwards S wave. The QRS complex represents ventricular depolarization and contraction. Amplitude: 5-30 mm high The QRS complex should be 1.5–2.5 small squares in duration Duration: 0.06 - 0.10 sec Waveforms T wave : T wave is normally a modest upwards waveform representing ventricular repolarization Amplitude: 0.5 mm in limb leads Duration: 0.1 - 0.25 sec Pathology of the heart Heart Failure Congenital Heart Disease Ischemic Heart Disease Hypertensive Heart Disease 1. Heart Failure End point of many heart diseases.Heart can’t pump blood fast enough to meet needs of body. System responds to failure by Releasing hormones (e.g., norepinephrine) Frank-Starling mechanism Hypertrophy Two types:- Right and left heart failure. Pathology of the Heart 2. Congenital Heart Disease Abnormalities of heart/great vessels present from birth Types :- 1-Left-to-right shunts atrial septal defects ventricular septal defects(Most common) Patent ductus arteriosus Pathology of the Heart 2-Right-to-left shunts tetralogy of fallot transposition of the great arteries. 3-Obstructions aortic coarctation Pathology of the Heart Ischemic Heart Disease (IHD) : Myocardial perfusion can’t meet demand. Usually caused by decreased coronary artery blood flow (“coronary artery disease”) Four syndromes: angina pectoris chronic IHD acute MI sudden cardiac death Pathology of the Heart Other heart diseases : 1-Valvular Heart Disease 2- Cardiomyopathies 3-Pericardial Disease 4-Tumors(rare) Pathology of the Heart ATHEROSCLEROSIS : This disease is responsible for more deaths and serious complications than any other disorder. This is because its prime targets are vital arteries, namely the coronaries, cerebral arteries, & the aorta. Accordingly the major consequences are : 1. Myocardial infarction 2. Cerebral infarction 3. Aortic aneurysm  Blood Pressure Hypertension is a major risk factor at all ages. Common problem (25% of population) Ranges :- 1-Normal blood pressure (adults) : < 140 mm Hg/90 mm Hg 2-Borderline HT : 140 - 160 mm Hg/90 - 95 mm Hg 3-Definite HT : > 160 mm Hg/95 mm Hg. Elevated blood pressure accelerates the process of atherosclerosis and increases the incidence of IHD and cerebrovascular diseases.  Blood Pressure Antihypertensive therapy reduces the incidence of atherosclerosis-related diseases, particularly IHD and CVA (cerebrovascular accidents; strokes). Clinical Notes What are the signs indicating that the patient has CVS problem? 1- Cyanosis. 2- Xanthelasma. 3- Led edema. Examinations Pulse :- rate , rhythm , volume 1- Rates :- 60-> 100 per minute Bradycardia/ normal / tachycardia. 2- Rhythm:- regular / irregular 3- Volume:- high / normal / low Examinations Where we can measure:- 1- radial 2- carotid 3- Brachial 4- femoral 5- popliteal 6- dorsalis pedis 7- posterior tibial Examinations Heart sounds (BY Stethoscope ) :- S1 + S2 + S3 + S4 Sites :- APT_M 2245 ?? A:- aortic valves second right intercostal. P:- pulmonary valves second left intercostal. T:- tricuspid valve left fourth intercostal. M:- mitral valve :- left fifth intercostal. JVP :- Jugular venous pulse ( in heart failure )  Cold body temperature ?!  Let’s Measure a Blood Pressure  End of the Second Lecture Do you have any questions?