Contenu connexe



  2. CARDIOVASCULAR SYSTEM  Is also called circulatory system  Consist of heart (muscular pumping device) & the vessels e.g. veins, arteries & capillaries  It begins to beat regularly early in the fourth week after fertilization  It continually propels oxygen, nutrients, wastes & many other substances into the interconnecting blood vessel supplying body organs
  3. LOCATION OF THE HEART  A four-chambered, shaped & sized like a persons closed fist  Lies in the mediastinum (middle region of the thorax) behind the body of the sternum, between the second rib to the fifth intercostal space.  Is about 12-14 cm
  4. LOCATION (CONT.)  Two third of its mass is to the left of the midline of the body & one third is to the right  Apex lie on the diaphragm, pointing to the left  Apical pulse can be felt, this is caused by the apex contracting the chest wall (on the fifth & six rib)  Base of the heart lie bellow the second rib
  5. SIZE & SHAPE  About size of the fist  Hollow cone-shape  It is broad, flat base or posterior surface about 9cm  At birth, it is transverse (wider) it appear larger as oppose to the diameter of chest cavity
  6. SHAPE & SIZE (CONT.)  Between puberty & 25yrs old, it attain its adult shape & weight, about 310g for males & 225g for females  In adult, its shape resemble that of the chest  For tall individuals, it is elongated, for short ones is transverse (wide)
  7. COVERING  Is covered by the pericardium, which consist of two parts 1. Fibrous portion: tough, loose fitting inextensible sac. Its functions are as follows:  Protect the heart  Prevent overfilling of the heart with blood  Anchor it to the surrounding structures.
  8. PARTS OF PERICARDIUM (CONT.) 2. Serous portion: lies inside the fibrous pericardium  It is thin & slippery & consist of two layers  Parietal layer lies inside the fibrous pericardium & visceral layer adheres to the outside of the heart  Pericardial space (cavity) with pericardial fluid separate the two layers
  9. THE HEART (CONT.) Functions of the heart covering  Provides protection against friction
  10. STRUCTURE/LAYERS OF THE HEART Three distinct layers of tissue make up the walls of the heart o Epicardium: outer layer of the heart wall, it is often infiltrated with fat in older people o Myocardium: is thick, contractile middle layer (layer that contracts). It compress the heart activities and blood within them with great force without fatigue
  11. LAYERS (CONT.) NB myocardium is thicker in some areas than the other o Endocardium: is a delicate inner layer of the endothelial tissue (type of a membranous tissue that lines the heart & blood vessels). Endocardium regulate the flow of blood through the chambers of the heart
  12. CHAMBERS OF THE HEART Is divided into four cavities  Two upper chambers are called atria/atrium  The lower chambers are called ventricles NB: chambers are separated by the septum,  Interatria septum (between the atria)  Intervetricular septum (between the ventricles)
  13. ATRIA  Called receiving chambers as they receive blood from the veins (are 3, superior, inferior vena cava & coronary sinus  It alternately relax & contract to receive blood then push it into the lower chamber  They move blood to a small distance, don’t need great pressure, so their myocardial wall is not very thick
  14. ATRIA  Four pulmonary vein enter the left atrium (are vein that transport blood from the lungs back to the heart  Auricle- earlike flap protruding from each atrium
  15. VENTRICLES  Two lower chambers known as “pumping chambers” or discharging chambers”  They push blood to the large network of blood vessels  Are thicker than atria because great force is needed to pump blood to a large distance  Left ventricle is thicker than the right as it push blood further
  16. VENTRICLES (CONT.)  Internal walls of ventricular chamber are irregular ridges of muscle called trabeculae carneae  Right V pumps blood into pulmonary trunk which transport the blood to the lungs  Left V ejects blood to the aorta (which is the largest artery (which is the largest artery in the body)
  17. VALVES OF THE HEART  Are mechanical devices that permit the flow of blood in one direction only (prevent back flow)  There are four sets of valves important to normal functioning of the heart I. Atrioventicular valves II. Semilunar valves III. Aortic semilunar IV. Pulmonary semilunar valve
  18. ATRIOVENTRICULAR VALVES  The right AV orifice consist of the three flaps (cup) of endocardium  Is also called tricuspid valve  Left AV orifice has two flaps (cup)  Is also called bicuspid (mitral) valve NB: AV valves prevent blood from flowing back into the atria from the ventricle when it contract
  19. SEMILUNAR VALVES  Half moon-shaped flaps growing out from the lining of the pulmonary artery & aorta  SL valves prevent blood from flowing back into the ventricles from the aorta & pulmonary artery
  20. VALVE (CONT.) - Aortic semilunar valve: valve at the entrance of the aorta  Pulmonary semilunar valve: valve at the entrance of pulmonary artery NB: all the valves open & close in response to the differences in pressure
  21. FLOW OR PATHWAY OF BLOOD THROUGH HEART  Has two side by side pumps (pulmonary & systemic circuit)
  22. BLOOD SUPPLY OF HEART TISSUE How the blood get nourishment?  It is regarded as a shortest circulation in the body  Myocardial cells receive blood right & left coronary arteries(which branch from aorta & via main branches)  Ventricles receive blood from branches of both right & left coronary arteries
  23. BLOOD SYPPLY (CONT.)  Most abundant blood supply goes to the myocardium of the left ventricle because the left ventricle does the most work & so needs the most oxygen & nutrients delivered to it  The right coronary supply the right side of the heart, this artery branches into two, the right marginal artery (supply the right side of the heart) & posterior interventricular artery(which run to the heart apex & supply posterior ventricular wall)
  24. BLOOD SUPPLY (CONT.)  Few anastomoses (connections exist between the larger branches of coronary arteries. If main route become obstructed, anastomoses provide collateral circulation to a part. NB there will be inadequate supply of nutrients  Complete blockage leads to tissue death & heart attack
  25. CARDIAC VEINS(VEINS OF CORONARY CIRCULATION)  Veins follow a course that closely parallels that of coronary artery  After going through cardiac veins, blood enters the coronary sinus to drain into the right atrium  Several veins drain directly into the right atrium
  26. CONDUCTION SYSTEM OF THE HEART  Heart has intrinsic system, is automatically stimulated without external stimulation  Consist of four structures – Sinoatrial (SA) node, Atrioventricular (AV) node, Atrioventricular (AV) bundle & the Purkinje fiber
  27. CONDUCTION (CONT.)  SA node (pace maker) : consist of hundreds of cells located in the right atrial wall near the opening of superior venacava Functions  Generate impulse about 75 times every minute  Sets the pace of the heart (determines the heart rate), they possess an intrinsic rhythm
  28. CONDUCTION (CONT.)  This means that without any nerve impulses from the brain & spinal cord, they themselves initiate impulse at regular intervals.  That means the firing of the SA node cause atrial contraction  AV node: small mass of special cardiac muscle tissue, lie in the right atrium along the lower part of the interatrial septum, is above tricuspid valve
  29. CONDUCTION (CONT.)  As the action potential enter the AV node from the right atrium, its conduction slows to allow complete contraction of both atrial chamber before the impulse reaches the ventricle  Meaning there is a delay here, electrical signal takes 0,1 of a second to pass through into the ventricle. This allows the atria to finish contracting before ventricles starts
  30. CONDUCTION (CONT.)  AV bundle (bundle of His)- originate in AV node, extend by two branches down the two sides on the interventricular septum, & continue as a purkinje fibers  After passing slowly through the Av node, conduction velocity increase as the impulse is relayed through the AV bundle into the ventricles
  31. CONDUCTION (CONT.)  Here, right & left bundle branches and the purkinge fibers in which they terminate conduct the impulses throughout muscle of both ventricles, stimulate them to contract almost simultaneously  Purkinge fibers extend out to the papillary muscle & lateral wall of ventricles
  32. CONDUCTION (CONT.)  NB: SA node initiates each heartbeat & set its pace- hence is called pace maker  The SA node normally drives the heart at the rate of 75 beats per minutes
  33. NERVE SUPPLY TO THE HEART  The heart is influenced by autonomic nerves originating in the cardiovascular center in the medulla oblongata which reach it through the autonomic nervous system  These consist of parasympathetic fibers combine to form cardiac plexuses located close to the arch of the aorta
  34. NERVE SUPPLY (CONT.)  The heart is influence by autonomic nerves originating in the cardiovascular center in the medulla oblongata which reach it through the autonomic nervous system  These consist of parasympathetic & sympathetic nerve & their actions are antagonistic
  35. NERVE SUPPLY (CONT.)  Both sympathetic fibers & parasympathetic fibers combine to form cardiac plexus located close to the arch of the aorta  From the cardiac plexus, fibers accompany the right & left coronary arteries to enter the heart  Most fibers end in the SA node, but some end in the AV node & in the atria myocardium
  36. NERVE SUPPLY (CONT.)  The vagus nerves supply mainly the SA & AV nodes & atria muscles. Parasympathetic stimulation reduces the rate at which impulses are produced, decreasing the rate & force of heart beat called (inhibitory or depressor nerves)
  37. NEARVE SUPPLY (CONT.)  The sympathetic nerve supply the SA & AV node & myocardium of the atria & ventricles.  Sympathetic stimulation increases the rate & force of the heart beat (are called the accelerator
  38. ELECTROCARDIOGRAM (ECG)  Is the graphic representation of cardiac conduction cycle  A graphic record of the heart electrical activity, its conduction of impulses, a record of electrical events that precedes the conduction of the heart  This record of electrical events must be interpreted to make a difference between life & death
  39. TO PRODUCE ECG  Electrodes of ECG are attached to a person  Changes in voltages are recorded that represent changes in the hearts electrical activity, are observed as deflection of a line drown on the paper or traced on the video monitor
  40. ECG (CONT.) Normal ECG has three distinguishable wave or deflection  P wave: is the first & small wave, which represent depolarization of the atria from the SA node. Last at about 0.08second. 0.1 second after the P wave begins, the atria contract
  41. ECG (CONT.)  QRS complex :represents depolarization of the ventricles & repolarization of the atria. That means the ventricle contracts & the atria relaxes. Duration of QRS complex is 0.08 second
  42. ECG (CONT.)  T wave: represent repolarization of ventricles. Duration of T wave last about 0.16 seconds. Repolarization is slower than depolarization that is why T wave has a lower height than QRS wave  NB: the measurement of the intervals between P, QRS & T wave can provide information about the rate of conduction of an action potential through the heart
  43. HEART SOUNDS  One is not conscious of his heartbeat unless he uses stethoscope below the left nipple to hear the heart beat  It make typical sound during each cardiac cycle like “lubb-dupp”  This is associated with the closing of heart valves  The pause between indicate period when the heart is relaxing
  44. HEART SOUND (CONT.)  Systolic sound: first sound caused by the contraction of the ventricles & by vibration of closing Atrioventricular valves. It is longer than diastolic sound  Diastolic sound: is short, sharp sound caused by vibrations of the closing of the semiluner valve at the beginning of the ventricular relaxation
  45. HEART SOUND (CONT.) NB: heart sounds have clinical significance because they give information about the functioning of the valves of the heart Abnormal heart sounds called murmurs, usually reflect valve problems
  46. THE CARDIAC CYCLE  The heart acts as a pump & its action consists of a series of events known as the cardiac cycle  Cardiac cycle means a complete heat beat  During each heart beat, the heart contracts & then relaxes  Period of contraction is called systole, that of relaxation is called diastole of both atria &both ventricles
  47. CARDIAC CYCLE (CONT.) NB: two atria contract simultaneously, then as the atria relax, two ventricles contract and then relax Cardiac cycle include all events associated with the blood flow through the heart during one complete heat beat- atria systole & atria diastole followed by ventricular systole & diastole
  48. PHASES OF CARDIAC CYCLE  Phase 1 Atria systole  Is the contraction of atria, there is a complete emptying of blood out of the atria into the ventricles  AV valves are open during this phase, semilunar valves are closed so that blood does not re enter from pulmonary artery or aorta
  49. PHASE 1 (CONT.)  Ventricles are relaxed & filling with blood  The cycle begin with P wave of the ECG
  50. CYCLE (CONT.)  Phase 2 Isovolumetric ventricular contraction  Occur between the start of ventricular systole (contraction of the ventricles) and the opening of semilunar valves  The ventricular volume remain constant as the pressure is increased rapidly
  51. PHASE 2 (CONT.)  The onset of ventricular systole coincides with the R wave of the ECG & the appearance of the first heart sound
  52. CYCLE (CONT.)  Phase 3 Ejection  Semilunar valves open & blood is ejected from the heart when the pressure gradient in the pulmonary artery & aorta  Reduced ejection is characterized by a less abrupt decrease in ventricular volume. coincide
  53. PHASE (CONT.)  Residual volume, normally remains in the ventricles at the end of ejection period
  54. CYCLE (CONT.)  Phase 4 Isovolumetric ventricular relaxation  Ventricular distole (relaxation) begin with this phase  Occurs between closure of the semilunar valve & opening of AV