Anatomy of Heart- Internal structures pt

This lecture consists of the anatomy of heart, layers, its valves and conduction system. It also includes coronary circulation and venous supply of heart.

1. Anatomy of Heart Ms. Saili Gaude Principal Shivam College of Nursing, Amirgadh

2. Heart It is the organ of circulation whose main work is to pump blood to all organs. It supplies blood to all parts of our body and receives blood from all over the body Helps keeps every cells in the body functioning It ensures that oxygenated blood reaches all part of the body And ensures that deoxygenated blood from tissues returns back to it. It is thus called an organ of the circulatory system as it circulates the blood in our body.

3. Heart The Greek term for heart is “cardia” Latin term for heart is “ cor ” for coronary These terms denotes heart

4. Location Inside thoracic cavity Middle mediastinum Behind the ribs behind sternum Lies in between the lungs Slightly more towards the left sternum

5. If the heart is situated more towards the right side than it may cause some problems due to its position and presence of associated structures. Levocardia Dextrocardia Left sided pointing of the heart Right sided pointing of the heart

6. Size Approximately the size of your fist Length Width Thickness 12cm 8cm 6cm

7. Weight Given the size difference between both genders : The weight of a female heart is approximately 250m to 300 g The weight of a male heart is approximately 300 to 350 g

8. Gross division Heart is an inverted triangle with its apex lying below and the base lie above.

9. Apex In anatomical term the tip of a triangle is called apex The apex lies below onto the diaphragm It is entirely formed by the part of the heart called left ventricles

10. Apex

11. Base of heart Lies above All major blood vessels enters the heart from the base Made up by the left atrium and a small part of the right atria

12. Base

13. Layers of heart Heart is made up of 3 layers

14. Layers of Heart

15. Pericardium Outermost layer of the heart A sac made up of 2 parts Both layers encloses the heart and roots of great vessels like aorta, pulmonary arteries etc. Fibrous pericardium Serous pericardium

16. PERICARDIUM

17. Present in the middle mediastinum Present even before the heart develops The heart grows into this layer during fetal development The last part to attach to the serous pericardium are the atrias

18. Fibrous pericardium Tough Made up of dense connective tissues Cone shaped Base is situated on the top of the diaphragm Apex is on top in continuity with the roots of great vessels

19. Borders Anteriorly : sternum Posteriorly : bronchi, esophagus and descending aorta Laterally : lungs, phrenic nerve

20. Pericardial apex Blunt Present at the sternal angle forming angle of louis

21. ANGLE OF LOUIS

22. Pericardial base Broad Lies on diaphragm attached to its central tendon Anteriorly attached to the sternum through sternopericardial ligament These attachments maintains the position of the heart Also overdistention of heart

23. STERNOPERICARDIAL LIGAMENT

24. Serous pericardium Thin double layered serous membrane Made up of mesothelium (membrane made up of simple squamous epithelium originating from the mesodermal cells of the embryo)

25. Serous pericardium Parietal pericardium attaches to the fibrous pericardium and the visceral pericardium attaches to the myocardium of the heart A small cavity is present in between these 2 layers called as the pericardial cavity

26. Pericardial cavity A potential space present in between the parietal and visceral pericardium Potential space – a space that exists even when 2 tissues are pressed against each other This pericardial cavity contains the pericardial fluid which prevents the heart from coming in direct contact with ribs Prevents friction between heart and ribs Normally there is 10 to 50 ml of pericardial fluid in the pericardial cavity If it becomes extra it compresses the heart and does not allow it to distend

27. Content of the pericardium Blood and nerves Ascending aorta Pulmonary trunk Superior and inferior vena cava Terminal ends of pulmonay veins

28. Myocardium Muscular layer of the heart Lies between pericardium and endocardium Most important layer of the heart Made up of specialized cells called the cardiomyocytes

29. Cardiomyocytes Cardio- heart Myo- muscles Cytes - cells

30. Cardiac muscles vs skeletal muscles Cardiac muscles Single nucleus Central nucleus Rich in glycogen and mitochondria Shorter in legth Skeletal muscles Multinucleated Peripheral nucleus Normal levels of glycogen and mitochondria Lengthier than cardiac muscle cells

31. Cardiac muscle fibres Each muscle fibre is attached to a plasma membrane called as sarcolemma Sarcolemma is an excitable membrane as it transports substances actively and helps in the transmission of electrical impulses There are smaller tubules inside this fibres called as the T tubules This T tubules are filled with calcium channels which allows faster exchange of calcium which further helps the heart in its contraction

32. Cardiomyocytes divides into many branches and while doing soo exposes an area of dark line called the intercalated disk This disk acts as a communication system between 2 cardiomyocytes Helps in easy transmission of action potential This muscle fibres are striated (strips) Attaches to fibrous skeleton

33. Endocardium Innermost layer Divided into 2 parts Subendocardium and endocardium

34. Subendocardium Outer most part Made up of connective tissues Heart’s electrical system is embedded into it

35. Endocardium Innermost layer Made up of endothelial layer

36. Internal division of the heart

37. Chambers of heart 4 chambers of heart 2 sides

38. GENERAL FEATURES On the upper surface of each atrium is a pouch like appendage called an auricle which is thought to increase the capacity of the atrium slightly. Thickness of the myocardium of the 4 chambers varies according to function Atrium are thin walled because they deliver blood into adjacent ventricles and the ventricles are equipped with thick muscular walls because they pump blood over greater distances

39. Even though the right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood, right side has a much smaller workload. This is because the right ventricle only pumps blood into lungs, which are close by and present little resistance to blood flow. On the other hand left ventricle pumps blood to rest of the body where the resistance to blood flow is considerably higher.

40. Consequently the left ventricle works harder than the right ventricle to maintain the same blood flow rate. This difference in workload affects the anatomy of the ventricular walls, the muscular wall of the left ventricle being significantly thicker than that of the right.

41. 4 chambers RIGHT SIDE 1. Right atrium 2. Right ventricles LEFT SIDE 1. Left atrium 2. Left ventricles

42. Right sided pump vs Left sided pump Right sided pump Right atrium Right ventricle Receives deoxygenated blood from all over the body Sends deoxygenated blood to lungs Left sided pump Left atrium Left ventricle Receives oxygenated blood from lungs Sends oxygenated blood to all parts of the body

43. Heart valves Heart consists of 4 valves which regulates and maintains blood flow in one direction only Prevents backflow of blood Flaps that opens and closes to allow and not allow blood flow The 4 valves are : Tricuspid valve Mitral valve Pulmonic valve Aortic valve valve

44. 1) Tricuspid valve: lies between the right atria and the right ventricles 2) Pulmonic valve : lies between the right ventricle and pulmonary trunk 3) Mitral valve : lies between the left atrium and left ventricles 4) Aortic valve: lies between left ventricle and aorta Right sided valves Left sided valves

45. Heart valves are divided into 2 1) a pair of atrioventricular valve which brings blood to ventricles 2) a pair of semilunar valves which drains blood out of the ventricles The heart valves are composed of connective tissue and endocardium

46. Atrioventricular valves The atrioventricular valves are located between the atria and ventricles They close during the start of ventricular contraction producing the first heart sound The mitral and tricuspid valves are supported by the attachment of fibrous cords called as the chordae tendinae The chordae tendinae are further attached to the papillary muscles located into the ventricles. Papillary muscles are nipple like muscular projections to which the chords are attached On contraction this papillary muscle contracts which causes the leaflets of the valve to prevent fall into the atria

47. Tricuspid valve It is situated in between the right atrium and right ventricle It allows deoxygenated to flow from superior vena cava & inferior vena cava- right atrium- tricuspid valve- right ventricles It has 3 cusps or leaflets that are supported to the margin of the valve. There is a fibrous ring surrounding the valve Fibrous ring diameter- 10 to 11cm Margin of valve- triangular There are 2 major and 1 minor papillary muscle attached to the tricuspid valve

48. Mitral valve 2 leaflet In between left atrium and left ventricles Contains annulus , chordae tendinae , papillary muscles and commisueres . Allows blood to enter from left atrium to left ventricles. Its closure along with the closure of tricuspid valve causes first heart sound called S1 sound.

49. SEMILUNAR VALVES The left and right ventricles pump out blood via pulmonary and aortic orifice (hole) respectively Each of these orifices is guarded by 3 semilunar cusps These cusps are directly connected to the wall of aorta or pulmonary trunk

50. PULMONARY VALVE Located between right ventricle and pulmonary artery When closed it prevents the back flow of blood to be pumped from right ventricle to the pulmonary artery The valve consists if 3 cusps named right , left and anterior Blood passes in a U shaped direction

51. AORTIC VALVE Located between left ventricle and aorta When closed it prevents the back flow of blood to be pumped from left ventricle to the aorta The valve consists if 3 cusps named right , left and anterior

52. CONDUCTION SYSTEM OF HEART

53. Features of heart Cardiac muscles shows 4 properties 1. Auto rhythmicity 2. Conductivity 3. Excitability 4. Contractility

54. AUTO RHYTHMICITY Heart initiates its own impulse at constant rhythm Contractions of the heart are controlled by specialized cardiac muscle cells called pacemaker cells which controls the heart rate. The pacemaker cells responds to signals from autonomic nervous system to speed up or slow down the heart rate

55. CONDUCTIVITY A network of specialized muscle cells is found in the heart’s walls. These muscle cells send signals to the rest of the heart muscle causing a contraction Each cell of the cardiac muscles have the ability to conducts the impulses to the next cells. These property of the cells is called as conductivity

56. EXCITABILITY It is the ability of a cardiac cell to generate an action potential at its membrane in response to depolarization and to transmit an impulse along the membrane.

57. CONTRACTILITY It is the ability of the cells to make it shorter or longer to pump the blood out of the heart

58. Conduction system of heart 1. Sinuatrial node 2. Atrioventricular node 3. Arioventricular bundle (Bundle of His) 4. Purkinje fibres

59. Sinuatrial node Location: in wall of right atrium right to opening of superior venacava Dimensions: 15 x 2 x 1mm Impulses are generated in this node It flat ellipsoid in shape Receives blood supply from sinoatrial artery

60. Atrioventricular node Location: Just beneath the endocardium on right side of lower part of atrial septum Conveys impulses from SA node to the ventricles Oval in shape 7x3x1mm in size Causes a slight delay in contraction of ventricles which is why the atria contracts before the ventricles

61. Atrioventricular bundle Arises from AV node and divides into right and left ventricles It carries impulses to the Purkinje fibres of the right ventricles and the left ventricles 1.8cm long

62. Purkinje fibres Spread deep to endocardium and reach all parts of ventricles including bases of papillary muscles Located in the inner ventricular walls of heart just beneath the endocardium into the subendocardium Composed of electrically excitable cells They are larger than cardiomyocytes with fewer myofibril and mitochondria

63. CORONARY CIRCULATION BLOOD SUPPLY OF HEART

64. Coronary circulation It is the circulation of blood in the blood vessel of the heart muscles The coronary arteries delivers oxygen rich blood to the myocardium Cardiac vein remove the deoxygenated blood from the heart muscles 1. Arterial supply 2. Venous drainage

65. Coronary arteries The blood flows through these arteries during diastole of heart Coronary blood flow is regulated mostly by local arteriolar vasodilation in response to nutritional need of cardiac muscle Daimeter is 1.5mm to 5.2mm Left coronary is larger in caliber and supplies more myocardium

66. Right coronary artery It arises from the right anterior aortic sinus of ascending aorta It passes between the right auricle and pulmonary trunk Branches 1. Atrial branch 2. Right marginal branch 3. Posterior inter- ventricular branch

67. Left coronary artery It originates from left posterior aortic sinus of ascending aorta It passes between pulmonary trunk and left auricle before entering the coronary sulcus Branch 1. Anterior inter ventricular branch (left anterior descending artery) 2. circumflex branch

68. Cardiac dominance In about 10 % of hearts, the right coronary artery is rather small and is not able to give posterior inter ventricular branch In these cases,the left coronary artery provides the posterior inter ventricular branch Such cases are left dominant

69. VENOUS DRAINAGE Coronary sinus Anterior cardiac vein Venae cordis minimae

70. Coronary sinus Coronary sinus is the largest vein of the heart It is responsible for draining most of the deoxygenated blood of the myocardium into the right atrium

71. Anterior cardiac veins These are variable number of small veins usually 2-5 which drains blood from the anterior portion of the right ventricle into the right atrium

72. Venae cordis minimae These are number of small veins in the walls of all of the heart chambers. They originates within the myocardium and pass deeply through the endocardium of the nearest chamber.

73. NERVE SUPPLY

74. Nerve supply Sympathetic nerve and parasympathetic nerves innervates the heart The network of nerves supplying the heart is called the cardiac plexus It receives contributions from the right and left vagus nerve as well as contributions from the sympathetic trunk These are responsible for influencing heart rate, cardiac output and contraction forces of the heart

75. Parasympathetic efferent fibres Name of nerve : Vagus nerve Function: Reducing heart rate Reducing force of contraction of the heart Vasoconstriction of the heart

76. Sympathetic efferent fibres Name of nerve: Cardiac nerve Function: Increasing heart rate Increasing the force of contraction

77. Afferent parasympathetic fibres Name of nerve: Vagal cardiac nerves Functions: Feedback on blood pressure

78. Afferent sympathetic fibres Name of nerve : afferent nerve of the upper thoracic and cervical ganglia Function: Feedback on blood pressure and pain sensation