ANATOMY AND PHYSIOLOGY OF HEART

IT IS BRIEF REVIEW ABOUT ANATOMY AND PHYSIOLOGY OF HEART.

1. By- AHMED SODHA M.Sc.(N) heart

2. The heart is a roughly cone shaped hollow muscular organ. Length: 10 cm Weight: 225 g in women 310 g in men Position/location: the heart lies in the thoracic cavity in the mediastinum( the space between two lungs). It lies obliquely little more to the left that right and presents a base above and apex below . introduction

3. I nferiorly: the apex rests on the central tendon of the diaphragm. Superiorly: the great blood vessels e.g. aorta, superior venacava , pulmonary artery and pulmonary veins Posteriorly: the oesophagus, trachea, left and right bronchus, descending aorta, inferior venacava and thoracic vertebra Laterally: the lungs- the left lungs overlaps the left side of the heart Anteriorly: the sternum , ribs and intercostal muscles. Organs associated with the heart

4. The heart wall: The heart wall is composed of three layers of the tissue. Pericardium Myocardium endocardium Structure of the heart

5. The pericardium is the outermost layer of the heart and is made up with two sacs. Outer sac consist of : fibrous tissue Inner sac consists of : continues double layer of serous membrane Outer layer is known as parietal pericardium Inner layer is known as visceral pericardium. the space between two sacs is known as pericardial space, which is filled with serous fluid, which is secreted from serous membrane of inner sac. 1. pericardium

6. The myocardium is composed of specialised cardiac muscles founded only in heart. It is not under voluntary control but striated like skeletal muscle. Each fibres cells has nucleus and one or more braches. The sheet arrangements of the myocardium enables the atria and ventricular to contract in a co ordinated and efficient manner. Myocardium is network of specialised conducting fibres responsible for transmitting the heart electrical signals. Myocardium is thickest at the apex and thins out towards the base. 2. myocardium

7. This lines the chambers and valves of the hearts. It is a thin smooth membrane to ensure smooth flow of blood through the heart. It consists of flattened epithelial cells and it is continuous with the endothelium lining the blood vessels . 3. endocardium:

8. The heart is divide into right and left sided by the septum, a partition consisting of myocardium converted by endocardium. Each side is divide by an antrioventricular valve into upper atrium and the ventricle below. Atrioventricular valve: these are formed by double layer of endocardium. Strengthen by a little fibrous tissue. Interior of the heart

9. AV VLAVES: right side AV valve has three flaps is known as tricuspid valve, which separates right atrium and right ventricle. Left sided AV valve has two flaps is called as mitral valve or bicuspid valve, which separates left atrium and left ventricle.

10. There are four chambers of the heart. 1. right atrium – 2- 3 mm size 2.rigth ventricle-4-5 mm 3. left atrium – 2-3 mm Left ventricle- 10-15 mm Chambers of the heart

11. The two largest veins of the body, the superior vencava and inferior vencava empty their contents into the right atrium. This blood passes via right atrioventriculer vlave into right ventricle and from there blood is pumped out into the pulmonary artery( the only artery in the body which caries deoxygenated blood). Blood flow through the heart

12. At the opening of pulmonary artery pulmonary valve is present which prevents backflow of the blood into right ventricle , it is also known as semi- luner valve. After leaving the heart the pulmonary artery divides into left and right pulmonary arteries, which carry the blood to the lungs where exchange of gases takes place, carbon dioxide excreted and oxygen is absorbed.

13. After purification of blood in the lungs two pulmonary veins carry oxygenated blood back to the left atrium. Blood than passes through left atrioventriculer valve ( mitral valve, bicuspid valve) into the left ventricle and from there blood Is pumped out into the aorta( the first artery of general circulation). The opening of aorta is guarded by the aortic valve.( at the opening of aorta there are valve present which is called as semilunar or aortic valve.

14. However , it should be noted that both atria contract at the same time and this followed by the simultaneous contraction of both ventricle s.

15. arterial supply: the heart I supplied with arterial blood by the right and left coronary arteries. The coronary arteries branch from the ascending aorta. The coronary arteries receives about 5% of the blood pumped from the heart. Large amount of blood supply especially to the left ventricle. There are two coronary arteries : Right coronary artery Left coronary artery Blood circulation to the heart/ coronary circulation

16. 1. right coronary artery: It supplies small branches to the right side heart. Right arteries having two branches: Posterior inter ventricular branch Marginal branches The posterior inter ventricular branches supplies blood to the wall of two ventricles. The marginal branches supplies blood to the right ventricles.

17. 2. left coronary artery: The left coronary artery passes inferior to the left circle & divides into the anterior inter ventricular branch & the circumflex branches. The anterior inter ventriculer branches will supplies oxygenated blood to the walls of both ventricles. The circumflex branch will supplies oxygenated blood to the walls of the left ventricle & left atrium.

18. Venous drainage: most of venous blood is collected into number of cardiac veins that join to form the coronary sinus, which opens into the right atrium .

19. Autorythmicity : THE heart posses the property of generating its own electrical impulse & beats independently of nervous or hormonal control. It is sullied with both sympathetic & Para sympathetic automic nerve fibres. Components: SA NODE: sino -atrial node AV NODE: atrio -ventricular node AV bundle( bundle of his): atrio ventricular bandle Conductive system of heart

20. SA NODE: SINO ATRIAL NODE This is small mass of specialise cells lies in the opening of the superior venacava . The Sino atrial cells generates these regular impulses because they are electrically unstable. This is also known as parameters. AV NODE: atrioventriculer node This is small mass of neuromuscular tissue is situated in the wall of the atrial septum near the arioventricular valve. Normally AV node merely transmit the electrical signals from the atria into ventricle.

21. 3. atriovenriculaer bundle( bundle of his) This mass of specialised fibres originated from the AV node. The AV node crosses the fibrous ring that separates atria and ventricles , then at the upper end of ventricular septum, it divides into right and left bundle branches. Within the ventricular myocardium the branches break up into the fibres called parkinje fibres, which supplies electrical impulses into the apex of the heart .

22. Heart is influenced by the autonomic( sympathetic & para sympathetic nerves originating in the cardiovascular centre in the medulla oblongata. The vegus nerve: supply mainly the SA node & AV nodes & atrial muscles. Nerve supply to the heart

23. The cardiac cycle:

24. At rest the healthy adult heart is likely to beat at a rate of 60-70 bpm . Each heart beat cycle is known as cardiac cycle . During this time heart will contract & relax. The period of contraction is called as systole & relaxation is called as diastole.

25. Each cardiac cycle lasts about 0.8. sec consists of : 1.Atrial systole: contraction of atria 0.1 sec 2. Ventricular systole : contraction of ventricles 0.3 secs 3. Complete cardiac diastole: Relaxation of atria & ventricles 0.4 secs Stages of cardiac cycle

26. The superior venacava & inferior vencava transport deoxygenated blood into the right atrium at the same time four pulmonary veins bring oxygenated blood into the left atrium. Through AV valves Blood flows passively into left ventricle(SA node spreads a wave of impulse into myocardium of left atrium & starts) Atrial contraction AV node spreads , impulses quickly into ventricular muscle via the AV bundle & purkinje fibres

27. A wave of contraction sweeps upward from apex of the heart across the both ventricles Ventricular contraction Blood pumps into pulmonary artery & aorta After contraction of ventricles the atrium & ventricles relax Myocardium recover in preparation for the next heartbeat & atria refill for next cycle

28. Heart sound is a involuntary action. There are four heart sounds. Each corresponding to a particular event in the cardiac cycle. LUB : first sound , fairly loud occurs due to closure of atrioventriculer vlave . DUP : softer , sound due to closure of aortic and pulmonary valves. Heart sound

29. It is the report of electrical activity of the heart. The pattern of electrical activity may be displayed on an oscilloscope screen or traced on paper. The normal ECG showing five waves by convention , have been named PQ,R,S, &T. P wave : it arise when impulse from the SA NODE sweeps over the atria( atrial depolarisation) The QRS wave : it represent the very rapid spread of the impulse from the AV node through the a bundle & the purkinjie fibres & the electrical activities of the ventricular muscle. ECG: ELETROCARDIOGRAM

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31. T WAVE : it represents the relaxation of the ventricular muscle.( ventricular repolarization) The ECG described above originated from the SA NODE and is known as sinus rhythm. P: atrial contraction QRS: ventricular contraction T: ventricular relaxation

32. The cardiac output is the amount of blood ejected from each ventricle every minute. The amount of blood expelled by each contraction of each ventricle is the stroke volume. Cardiac output is expressed in litters per minutes. Cardiac out put = stroke volume * heart beat In healthy adult heart at rest the stroke volume is approximately 70ml and per minute heart rate is 72 per minute Cardiac out put will be 5 liter / minute Cardiac output

33. Venous return strength of myocardial contraction Blood volume factors affecting stroke volume

34. Blood pressure is the force pressure that the blood exerts on the walls of the blood vessels. Blood pressure varies according to the times of the day, posture, gender, age of the individual. Blood pressure= systolic pressure diastolic pressure Systolic pressure: When the left ventricular contracts & pushes blood into the aorta, the pressure produced within the arterial system is called the systolic blood pressure. In adult it will be 120 mm of Hg or 16 Kpa ( kilo paskal ) Blood pressure

35. Diastolic pressure: When complete cardiac diastole occurs & the heart is resting following the ejection of the blood , the pressure within the arteries is much lower & is called diastole blood pressure. In adult it will be 80 mm of Hg 0r 11 Kpa . BP= 120 mm of HG/ 80 mm of Hg Blood pressure = cardiac output * peripheral resistanc e

36. blood pressure is controlled in two ways. 1. short term control: Moment to moment basis which mainly involves 1. baroreceptor reflex 2. chemo receptor reflex 3. higher centres in the brain 2. Long term control: it involves regulation of blood by kidney and renin angiotensin – aldosterone system( RAAS ) Control of blood pressure

37. Cardio vascular centre (CVC) : it is collection of interconnected nervous in the brain & situated in the medulla & pons. BARORECEPTORS : These are nerve ending sensitive to pressure changes ( stretch) within the vessel, situated in the arch of aorta and in the carotid sinuses.( these are body’s principal moment to moment regulatory mechanism for controlling blood pressure. 1. Short term BP regulation

38. Chemoreceptors: these are the nerve ending situated in the carotid and aortic bodies. 1. BARORECEPTORS: When BP increases(BP more than 120 mm of hg) Stimulation of baroreceptors in the aorta Sending the impulses in to the cardiovascular centre in the brain CVC stimulates the parasympathetic nervous system Relaxation of muscle of blood vessels ( tunica media) Vasodilation Blood pressure will decrease

39. when BP decreases less than 120/80 mm of Hg Stimulation of brain receptors in the aorta Sending impulses into the CVC in the brain CVC will pass message into sympathetic nervous system Stimulation of sympathetic nerve system Contraction of muscles of blood vessels ( tunica media) Vasoconstriction BP will increase

40. When co2 level increases & O2 level decrease in the blood stream Tissue hypoxia Need to improve tissue perfusion Blood pressure should increase in this situation, chemoreceptor will recognize this changes in CO2 & O2 in the blood stream. Pass this contraction to CVC in the brain CVC will stimulate sympathetic nerve system Vasoconstriction BP will increase CHEMORECEPTORS:

41. when emotional status such as fear, anxiety, pain , anger, occurs. Hypothalamus will get stimulated Brain need more blood supply It will stimulate sympathetic nerve system Vasoconstriction BP increases thus brain will get more blood supply, Higher centre in the brain

42. RAAS: renin angiotensin – aldosterone system It is the mechanism where involvement of kidney is possible. When kidney is unable to get blood supply , only this mechanism will be activated. Low renal blood flow Decreased blood volume Decreased BP Kidney will secret renin Angiotensinogen _____ angiotensin I ACE Long term mechanism

43. Angiotensin II Adrenal cortex vasoconstriction Secretion of aldosterone increased BP Kidney tubules reabsorbs kidney will get adequate blood supply Na & water Increased blood volume Increased BP

44. Although circulation of blood around the body is continues. It is described into two parts. A. pulmonary circulation B. systemic circulation Circulation of blood

45. This consist of the circulation of blood from the right ventricle of the heart to the lungs & back to the left atrium. The pulmonary arteries: there are two branches for the pulmonary trunk, 1. right pulmonary artery: it passes to the root of the right lungs & divides into the branches. - larger branches carries blood into middle & lower lobes - smaller branches carries into upper lobe 2. the left pulmonary artery; it runs to the left lungs where it divides into two branches. One passing into each lobe . a. Pulmonary circulation

46. Within the lungs these arteries divides & subdivide into smaller arteries, Arterioles Capillaries the inter change of O2 & CO2 takes place between capillary blood & air in the alveoli of the lungs. After gas exchanges each capillaries will join together & forms vessels. Capillaries Veinules veins

47. there are two pulmonary veins. Right & left pulmonary veins This both will carry oxygenated blood into left atrium of the heart.

48. It is the circulation of blood all around the body. The blood pumped out from the left ventricle is carried by the branches of the aorta around the body & is returned to the right atrium of the heart by superior & anterior vencava is known as systemic circulation. 2. Systemic / general circulation

49. Blood vessels are acting as pumps to supply blood through out the body. Blood vessels vary in structure size, function & these are several types Arteries Arterioles Capillaries Venules veins Blood vessels

50. These are the blood vessels that transport blood away from the heart. They vary in considerably in size & their wall consist of their layers of tissue. Tunica adventitia : outer layer : fibrous tissue Tunica media : middle layer: smooth muscle & elastic tissue Tunica intima : inner layer: squamous epithelial tiss ue Arteries & arterioles

51. Anastomosis are arteries that form a link between main arteries supplying an area. End arteries are the arteries with no anastomoses or those beyond the most distal anastomosis. ANASTOMOSIS & END ARTERIES

52. The smallest arterioles break into a number of minotic vessels called capillaries. The walls consist of a single layers of endothelial cells sitting on a very thin basement membrane. Through which water & other small molecules can pass. Entry to capillaries bed is grounded by rings of smooth muscle( pre capillary sphincters) that directs the blood vessels. In certain places, including liver & bone marrow, the capillaries are significantly wider & thicker than normal. These are known as SINUSOIDS. Capillaries & sinusoids

53. Veins are blood vessles that returns blood at low pressure to the heart. The walls of the veins are the thinner than those of arteries but have the same three layers of tissue. Veins are having valves, which prevent backflow of blood. These are formed by folds of tunica intima & strengthen by connective tissue. Smallest veins are called as venules . Veins & venules

54. The outer layer of tissue of thick walled blood vessels receive & the their blood walled blood supply via network of blood vessels called the vasa vasorum . Thin walled vessels & the endothelium of other receives O 2 & nutrients by diffusion from the blood passing trough them. Blood supply

55. Vasomotor centre in medulla oblongata Autonomic nerve system Sympathetic stimulation para sympathetic stimulation Contraction of smooth relaxation of smooth muscle tunica media muscle of tunica media Vasoconstriction vasodilatation Lumen of blood vessel lumen of blood vessel increase decreased Nerve supply

56. The aorta is biggest artery in the human body & begins at the upper part of the left ventricle & passing up wards for short way , it arches back wards and to the left. It then descends behind the heart through the thoracic cavity a little to the left of the thoracic vertebrae. At the level of 12 th thoracic vertebra it passes behind the diaphragm then downwards in the abdominal cavity to the level of 4 th lumber vertebra, where it divides into the right and left common iliac arteries. AORTA

57. The aorta will be described here according to its location. 1. thoracic aorta: This is the part of aorta lies above the diaphragm and is described in three parts. - ascending aorta - arch of aorta - descending aorta in the thorax

58. A. ascending aorta: It is about 5 cm long , lies behind the sternum. Two blood vessels stating from ascending aorta that are, right and left coronary artery.

59. B. Arch of aorta: The arch of aorta is continuation of ascending aorta. It begins behind the manubrium of the sternum and runs up wards, back wards and to the left in front of trachea. And it is continuous with the descending aorta . - brachiocephalic artery -Left common carotid artery -Left subclvian artery

60. The venous blood from head & neck is returned by deep & superficial veins. The superficial veins will drain blood from superficial area of the brain & deep vein drain from deep area of deep of brain. Veins of head and neck: 1. right and left middle temporal vein 2. right and left supra orbital veins 3. right and left maxillary vein 4. right and left facial vein 5. right and left lingual vein 6. right and left occipital veins Venus returns from the head & neck

61. The greater part of the brain is supplied by arrangement of arteries called the circle of willis . It consist of following arteries: Two internal carotid arteries Two vertebral arteries Circulus arteriosos (circle of willi )

62. Circulation of blood to upper limb:

63. The veins of upper limb is divided into two groups: 1. Deep veins: Metacarpal veins Deep palmar venous arch Brachial veins Axillary veins 2. Superficial veins Cephalic vein Basilica veins Median veins Medial cubital veins Both join together & forms subclavian veins. Venus supply:

64. This is the part of aorta which continuous with arch of aorta & begins at the 4 the thoracic vertebra & extends downwards on the anterior surface of the thoracic vertebra. The descending aorta in the thorax gives of many paired branches those are, Bronchial arteries: supply to brachia & lungs Oesophagus arteries: oesophagus Intercostal artery: ribs, intercostal muscles DESCENDING AORTA:

65. There are two veins to drain venous blood in thoracic cavity. Azygos vein & hemizygos vein The brachial vein, oesophageal vein & intercostal vein join together & forms these two main veins. Azygos vein joins with superior venacva & hemizyagose vein join with left brachiocephalic vein. Venous returns:

66. The abdominal aorta is the continuation of thoracic aorta& entering behind diaphragm at the 12 th thoracic vertebrae , at the level of 4ht lumber vertebrae. it will divide into two common iliac artery. Many branches arises from the abdominal aorta. Paired branches: Inferior phrenic artery : diaphragm Renal artery: kidney Superior renal artery: adrenal gland Testicular artery: testes Ovarian artery: ovary ABDOMINAL AORTA:

67. Unpaired branches: 1. The coeliac artery : is short, thick, 1.25cm long & it rises immediate below the diaphragm 7, divides into 3 branches. Left gastric artery : stomach Splenic artery : pancreas & spleen Hepatic artery : liver, gall bladder, duodenum 2. Superior mesenteric artery: It is a branch from aorta between the coeliac artery & renal artery & supply blood supply to small intestine & proximal part of large intestine . 3. Inferior mesenteric artery: It arises from aorta about 4cm above its division into common iliac artery. It supplies distal half of large intestine & part of rectum.

68. Paired testicular, ovarian, renal & adrenal veins join into directly inferior venacava . Blood from remaining organs in the abdominal cavity passes through the liver via PORTAL CIRCULATION & enter into interior venacva . Venus return:

69. In the portal circulation, venous blood passes from the capillary beds of the abdominal part of the digestive system, spleen, pancreas to the liver. In this way blood with a high concentration of nutrients, absorbed from the stomach and intestines goes to the liver first. In liver certain modification take place including the regulation of blood nutrients levels. It passes in second capillary bed , the hepatic sinusoids & from portal vein. PORTAL CIRCULATION:

70. PORTAL VEIN: This is formed by the union of the following veins, each of which drains blood from the area supplied by corresponding artery. Splenic vein : drains blood spleen , pancreas, part of stomach Inferior mesenteric vein : rectum, pelvic, descending colon of large intestine. Superior mesenteric vein : small intestine, proximal part of large intestine Gastric vein : stomach. Distal end of oesophagus Cystic vein : gall bladder

71. HEPATIC VEIN: These are very short veins that leave the posterior surface of the liver & almost immediately enter the inferior vencava .

72. Abdominal aorta will divide into right & left common iliac artery. These are divided into further two branches. Internal iliac artery External iliac artery Internal iliac artery: It will supply organs in the pelvic cavity. In female: uterine artery CIRCULATION OF PELVIS & LOWER LIMB:

73. External iliac artery: It will obliquely downwards & passes into where it divides femoral artery & branches into popliteal artery which supply blood to the knee area and popliteal fossa. It further divides into : The femoral artery: begins at midpoint at the inguinal ligament & extends downwards in front of the thigh. Then it eventually passes through popliteal space where it becomes the popliteal artery. Popliteal artery : it passes through the popliteal fossa behind the knee, where pulse can be felt. At lower border of the popliteal fossa it divides into the anterior and posterior tibial arteries.

74. Anterior tibial artery : which supplies blood supply to the tibia, ankle joint. It will divide over the dorsum of foot & forms dorsalis pedis artery. Posterior tibial artery : it runs medially back of legs & gives a branch peroneal artery which supplies lateral aspect of the leg & forms a new branch- planter artery, which supplies blood to the sole of the foot.

75. Right common iliac artery   Right internal iliac artery right external iliac artery   Scrotal artery - femoral artery Uterine artery -popliteal artery -Anterior & posterior tibial artery - Dorsalis pedis & pl planter arteries

76. 1 . Deep veins: Digital vein Planter venous arch Post tibial vein Anterior tibial vein Popliteal vein Femoral vein External iliac vein Internal iliac vein Common iliac vein Both right & left common iliac veins joins into inferior venacava at the sacro iliac joint. Venus return:

77. 2. Superficial vein : there are two main superficial veins are draining blood from the lower limbs are, Small saphenous vein: the small saphenous vein begins behind the ankle joint& joins into popliteal vein. Great saphenous vein : it is the longest vein of the body , it begins at the medial half of the dorsum of the foot & runs upwards crossing over thigh & joins into political vein.