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cardiovascular anatomy and physiology

  1. 1. Cardiovascular System Tariq Siraj Qazi Assistant Professor/ Principal JCN Abbottabad A&P-I Unit VIII
  2. 2. Objectives At the end of this session, the students will be able to: • Define blood and list its functions • Describe the composition, sites of production and functions of cellular parts of blood and plasma • Briefly explain the ABO blood groups & Rh factor. • Describe the location, structure and functions of the heart and its great blood vessels. • Discuss the blood flow through the heart • Describe the structure and functional features of the conducting system of the heart. • Describe the principal events of a cardiac cycle.
  3. 3. Objectives cont…. • Explain the structure and function of: • Arteries • Veins & • Capillaries • Describe the following types of blood circulation: • Pulmonary circulation • Systemic circulation (coronary & hepatic portal circulation).
  4. 4. Parts of the Circulatory System • Divided into three major parts: – Heart – Blood – Blood Vessels
  5. 5. Functions of C-V System • Circulate blood throughout entire body for – Transport of oxygen to cells – Transport of CO2 away from cells – Transport of nutrients to cells – Movement of immune system components (cells, antibodies) – Transport of endocrine gland secretions
  6. 6. Heart • Location: mediastinum and rests on the diaphragm. • Size: as much as one’s close fist. • Weight: 250 g in adult female and 300 g in male. • Structure: Cone shaped with pointed apex inferiorly to left and broad base superiorly to the right. ▪ Membranous Layers • Two Pericardiums as superficial fibrous pericardium of connective tissue and deeper serous pericardium of epithelial tissue connected with the fibrous pericardium. • Serous pericardium—Parietal and visceral membrane. • Pericardial cavity with pericardial fluid.
  7. 7. Layers of heart • —three layers 1. Outer Pericardium—membranous layer 2. Middle Myocardium—muscular layer 3. Inner Endocardium—endothelial layer Pericardium----fibrous and serous membrane Pericardial fluid----25 to 35 ml Myocardium----- three types of muscle fibers i. Pacemaker ii. Conductive system iii. Contractile
  8. 8. Serous membrane Continuous with blood vessels
  9. 9. Actions of the Heart • Actions of the heart are classified into four types: 1. Chronotropic action----Heart Rate 2. Inotropic action.......Force of contraction 3. Dromotropic action.......Conduction of impulse 4. Bathmotropic action.......Excitability of muscles
  10. 10. Chambers of the Heart ❑ Four chambers—two pumps ─ Two atria (superior) ─ Two ventricles (inferior) ❖ Right Pump ➢Right Atrium receives deoxygenated blood from three veins as: ─ Superior vena cava ─ Inferior vena cava ─ Coronary sinus • Interatrial septum—between right and left atrium
  11. 11. ➢ Right Ventricle: • Inside ridges called trabeculae carnae • Receives blood from right atrium via tricuspid valve (Right atrioventricular valve) • The cusps are connected to chordae tendineae. • Chordae tendineae are connected to papillary muscles. • The partition between right and left ventricle is interventricular septum. • Deoxygenated blood is pumped out through the pulmonary valve (p. semilunar valve) into a large artery called pulmonary trunk which divides into right and left pulmonary arteries.
  12. 12. ❖Left Pump ➢Left Atrium • It receives oxygenated blood from lungs through four pulmonary veins. • Passes blood to the left ventricle via bicuspid (mitral) valve or left atrioventricular valve. ➢Left Ventricle • The thickest chamber of the heart. • Forms the apex of the heart • Blood passes from the left ventricle through the aortic valve (aortic semilunar valve) into the ascending aorta. • Some blood from the ascending aorta flows into the coronary arteries.
  13. 13. Semilunar valves • They have three cusps. • They are located at the base of both the pulmonary trunk (pulmonary artery) and the aorta, the two arteries taking blood out of the ventricles. • These valves permit blood to be forced into the arteries, but prevent backflow of blood from the arteries into the ventricles. • These valves do not have chordae tendineae, and are more similar to valves in veins than atrioventricular valves.
  14. 14. Tricuspid Valve
  15. 15. • The “ lub” is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole. The second sound,” dub” or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole.
  16. 16. Chambers of the heart; valves
  17. 17. Valvular Disorders • Stenosis (= narrowing): Failure of a valve to close completely is called insufficiency or incompetence, e.g, Mitral stenosis or aortic stenosis in which there is backflow of blood. • Mitral Valve Prolapse (MVP): The protrusion of one or both cusps of the mitral valve into the left atrium during ventricular contraction. • Rheumatic fever, an acute inflammatory disease caused by streptococcal infection, is one of the causes of valvular disorders.
  18. 18. Conduction System • Specialized cardiac muscle fibers called autorhythmic fibers. • Self-excitable • Generate electrical activity (action potential). • Not dependent on nerves for stimulation. • Heart has its own intrinsic system.
  19. 19. These muscle fibers have two important functions 1. Act as a pacemaker (setting the rhythm of electrical excitation that causes the contractions) 2. Form the conduction system (a network of specialized cardiac muscle fibers) • The conduction system occurs as follows: 1. Sinoatrial (SA) node, located in the right atrial wall just inferior and lateral to the opening of the superior vena cava, generate electrical signals. 2. After atrial contraction the action potential reaches the atrioventricular (AV) node, located in the interatrial septum just anterior to the opening of the coronary sinus. 3. From the AV node, the action potential enters the atrioventricular (AV) bundle (also known as bundle of His)
  20. 20. 4. The AV bundle divides into right and left bundle branches and extending via interventricular septum toward the heart apex. 5. The right and left bundle branches finally divide into Purkinji fibers that conduct the action potential upward to the remaining of the ventricles.
  21. 21. Conduction System
  22. 22. Heart Conduction System
  23. 23. Cardiac Cycle Cardiac cycle consists of systole and diastole of atria and ventricles ❖Atrial Systole (Atrial contraction): • Lasts about 0.1 sec • At the same time, the ventricles are relaxed • Depolarization of the SA node causes atrial depolarization which is marked by P wave in the ECG. • Atrial depolarization causes atrial systole. • Blood is forced via AV valves into the ventricles.
  24. 24. Cardiac Cycle cont… • Atrial systole contributes 60 ml of blood to the volume of 40 ml already in each ventricle. • At the end of ventricular diastole, each ventricle has 100 ml. • This blood volume (100 ml) is called end- diastolic volume (EDV). • The QRS complex in the ECG marks the onset of ventricular depolarization. • The percentage of the EDV ejected (about 60%) is ejection fraction.
  25. 25. ❖Ventricular Systole: • It lasts about 0.3 sec • At the same time, the atria are relaxed. • Ventricular depolarization causes ventricular systole. • The T wave in the ECG marks the onset of ventricular repolarization. • The right and left ventricles eject about 60 ml of blood each into the pulmonary trunk and aorta respectively. • The blood volume remaining in each ventricle at the end of systole, about 40 ml, is the end-systolic volume (ESV). • Stroke volume (the volume ejected per beat by each ventricle) equals EDV minus ESV (SV=EDV—ESV ).
  26. 26. • Cardiac Output: The amount of blood ejected by each ventricle in one minute is called cardiac output (CO). • Cardiac output = Heart rate × Stroke volume • Pre-load: • Degree of tension on muscle when it begins to contract • Pre-load = end-diastolic pressure • After-load: Load against which muscle exerts its contractile force. • After-load = pressure in aorta and pulmonary trunk
  27. 27. CORONARY CIRCULATION • Heart is supplied by TWO CORONARY arteries: 1- Right coronary artery---(RCA) 2- Left coronary artery---(LCA) • These coronary arteries arise at the root of the aorta. 29
  28. 28. Coronary arteries & their branches ➢ LCA---- it passes under the left atrium and divides into two branches: 1. Circumflex Artery . It continues around the left side of the heart and supplies blood to the left atrium and posterior wall of the left ventricle. 2. Left Anterior Descending (LAD) • It gives off smaller branches to the interventricular septum and anterior walls of both ventricles. 30
  29. 29. Coronary arteries cont… ➢RCA ---- It gives off two branches: 1. Marginal Artery • It supplies blood to the lateral aspect of the right atrium and ventricle. 2. Posterior descending artery • It supplies blood to the posterior walls of both ventricles. 31
  30. 30. Coronary Arteries (Anterior view)
  31. 31. Coronary Arteries (posterior view)
  32. 32. CORONARY ARTERY DISEASE • Ischemic heart disease (IHD) (angina pectoris) • Myocardial Infarction • Angina pectoris: – there is reduced coronary artery blood flow due to atherosclerosis (cholestrol deposition -- Plaque) 35
  33. 33. 36 3 Major types of blood vessels • Body • RA • RV • Lungs • LA • LV • Boby 1.Arteries 2.Capillaries 3.Veins Arteries carry blood away from the heart -”branch,” “diverge” or “fork” Veins carry blood toward the heart -”join”, “merge,” “converge”
  34. 34. 37 General characteristics of vessels • Three layers (except for the smallest) 1. Tunica intima 2. Tunica media 3. Tunica externa or adventitia • Lumen is the central blood filled space
  35. 35. 38 • Intima is endothelium (simple squamous epithelium) • Tunica media: layers of circular smooth muscles – Lamina (layers) of elastin and collagen internal and external – Thicker in arteries than veins (maintain blood pressure) Smooth muscle contraction: vasoconstriction Smooth muscle relaxation: vasodilation
  36. 36. 39 • Adventitia (t. externa) – longitudinally running collagen and elastin for strength and recoil
  37. 37. 40 Capillaries Heart to arteries to capillaries to veins to heart • Capillaries are smallest – 8-10um – Just big enough for single file erythrocytes – Composed of: single layer of endothelial cells surrounded by basement membrane • Universal function – Oxygen and nutrient delivery to tissues – CO2 and nitrogenous waste removal • Some also have tissue specific functions
  38. 38. 41 Special features of veins • Valves – Prevent backflow – Most abundant in legs (where blood has to travel against gravity) • Muscular contraction – Aids the return of blood to heart in conjunction with valves
  39. 39. 42 Exercise helps circulation (because muscles contract and squeeze blood back to the heart)
  40. 40. 43 Vascular System (Blood vessels of the body) • Two circulations – Systemic – Pulmonary • Arteries and veins usually run together • Often nerves run with them
  41. 41. 44 Pulmonary Circulation • Pulmonary trunk branches – Right and left pulmonary arteries – Division into lobar arteries • 3 on right • 2 on left – Smaller and smaller arterioles, into capillaries surrounding alveoli • Gas exchange
  42. 42. 45 Pulmonary Circulation • After gas exchange blood enters venules • Larger and larger into Superior and Inferior Pulmonary veins • Four Pulmonary Veins empty into left atrium
  43. 43. 47 Systemic Circulation • Oxygenated blood to body • Leaves LV through Ascending Aorta – Only branches are the 2 coronary arteries to the heart • Aortic Arch has three arteries branching from it: 1. Brachiocephalic trunk, has 2 branches: • Right common carotid a. • Right subclavian a. 2. Left common carotid a. 3. Left subclavian a. Ligamentum arteriosum connecting to pulmonary a.
  44. 44. 48 • Hepatic portal system – Picks up digested nutrients from stomach & intestines and delivers them to liver for processing and storage • Storage of nutrients • Detoxification of toxins, drugs, etc. Tributaries of hepatic portal vein: -superior mesenteric vein -splenic vein -inferior mesenteric vein