The thorax plays a crucial role in respiration and protecting internal organs.pptx

The thorax is the region of the body between the neck and the abdomen, also known as the chest. It contains vital organs such as the heart and lungs, as well as other structures like the ribs, sternum (breastbone), and thoracic vertebrae.

1. The Thorax 4/10/2024

2. Outline Introduction Thoracic wall Skeleton of thorax Muscles of the thoracic wall Nerves of the thoracic wall Vasculature of the thoracic wall Thoracic cavity Pleurae Lungs Mediastinum pericardium Heart Great vessels 4/10/2024

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4. Introduction Thorax is the superior part of trunk between neck and abdomen Contains heart and great vessels, lungs , thymus , trachea and esophagus Clinical examination of chest requires a good knowledge of its structure and vital organs it contains Function Provides a protective cage around the vital organs (heart, lungs, great blood vessels) Provides support for the shoulder girdles Bony attachment points for muscles of the back, chest and shoulders Helps for breathing to happen 4/10/2024

5. Thoracic wall The thoracic wall consists of skin, fascia, nerves, vessels, muscles, and bones The superior thoracic aperture bordered by vertebra TI, 1 st rib, and the manubrium of sternum The inferior thoracic aperture bordered by vertebra T12, 12 th rib, the end of rib 11, the costal margin, and the xiphoid process of sternum 4/10/2024

6. Skeleton of thorax Forms : osteocartilaginous thoracic cage Includes: 12 pairs of ribs and costal cartilages :- Form lateral boundaries 12 thoracic vertebrae and intervertebral discs Sternum:- form anterior boundary with costal cartilages 4/10/2024

7. Skeleton of thorax: The Sternum Flat bone lies in the anterior midline of the thorax It consists of three fused bones Manubrium Body Xiphoid process 4/10/2024

8. The Sternum Manubrium Located at level of T3-T4 Has Jugular (sternal) notch Articulate with clavicle at Clavicular facets Sternal Angle –articulate 2 nd rib which is a major surface landmark used by clinicians Lies opposite 2 nd costal cartilage: guide to numbering of ribs Body Articulates with ribs 2-7 Located at level of T5-T9 Xiphoid process Sword-shaped Cartilaginous at birth Landmark: inferior limit of thoracic cavity 4/10/2024

9. The Ribs 12 pairs 1-7 th ( True ribs ) - have direct attachment to sternum Ribs 8-10 th - ( F alse ribs ) – have indirect attachment to sternum Ribs 11-12 th- have no anterior attachments - floating ribs Structurally: Typical Ribs Ribs # 3-9 Atypical Ribs Ribs #1, 2, 10 , 11, 12 Intercostal spaces lie between adjacent ribs and are filled by intercostal muscles 4/10/2024

10. Rib Anatomy Typical Ribs have Head (2 facets) Neck Tubercle Angle Shaft Costal Groove:- on inferior border Costal cartilages 4/10/2024

11. Atypical Ribs #1-short, wider, posses subclavian groove , no angle 2 nd rib- has tuberosity for serratus anterior 1 st ,10 th &12 th ribs have only one facet on their heads and articulate with a single vertebra rib 11 , 12- are short and have no neck or tubercle 4/10/2024

12. Thoracic Vertebrae The thoracic vertebrae have the following features Body = heart shaped Vertebral arch ( neural arch )= around vertebral foramen : composed of 1- pedicle ( joining body to transverse process ) 2 -transverse process (lateral projection of arch) 3- lamina ( joining transverse and spinous process ) 4- the spinous process ( posterior projection , point inferiorly ) 5. Articular process Transverse Costal Facets : on the transverse process. vertebral foramen : circular passage enclosed in Vertebral arch and contains spinal cord Intervertebral disc:- are cushion like pads interposed between vertebrae 4/10/2024

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14. Muscles of the thoracic wall Intercostal spaces contain 3 layers of muscles: External intercostal muscles Internal intercostal muscles Innermost intercostal muscles All are innervated by intercostal nerve All arise from i nferior border of the rib above and inserted in to s uperior border of the rib below 4/10/2024

15. Thoracic Muscles External Intercostals Not complete anteriorly (anterior intercostal membrane replaces at Costochondral joints) Fibers run OBLIQUE (downward and forward) Aid in Inspiration (lift ribcage, increase dimensions) 4/10/2024

16. Internal intercostals Occupy intercostal spaces from sternum to angles of ribs posteriorly replaced by internal intercostal membranes Action - draws ribs together aids in respiration Muscle fibers project superiorly in a posterior to anterior direction (perpendicular to fibers of external intercostals) 4/10/2024

17. Innermost intercostal Similar to internal intercostal; deep portions of them Separated from internal intercostals by intercostal nerves and vessels 4/10/2024

18. Subcostal muscles Variable in size and shape Extend from internal surface of angle of ribs to internal surface of the rib below crossing one or two intercostal spaces Act as internal intercostal mm 4/10/2024

19. Transversus thoracis Origin - from the back of the sternum and the xiphoid process Insertion – on to costochondral junctions of ribs 3-6 Weakly depress ribs 4/10/2024

20. Thoracic Muscles cont’ed Serratus posterior :- innervated by intercostal nerve Serratus posterior superior O-Spinous process of C6 ---T2 I- Rib 2—5 (lateral to angle of rib) A- elevate ribs Serratus posterior inferior O-spinous process of T11---L 2 I- Rib 9—12 (lateral to angle of rib) A- depress ribs Levator costarum (innervated by posterior rami) O-tip of transverse process of C7---T11 I-lateral to tubercle of rib below elevate ribs 4/10/2024

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22. Nerves of thoracic wall 12 pairs of thoracic spinal nerves Leave spinal cord through corresponding intervertebral foramina and divide into 2 branches Posterior (dorsal) rami : innervate muscles, bones, joints and skin of the back Anterior (ventral) rami : innervate intercostal musculature, periosteum of the ribs and skin of the thorax Ventral rami of T1-T11=intercostal nerves Ventral ramus of T12 = subcostal nerve 4/10/2024

23. Branches Muscular branch Collateral supply intercostal muscles Cutaneous anterior + lateral Communicating connect each nerve to sympathetic trunk 4/10/2024

24. Vasculature of thoracic wall Intercostal arteries Intercostal vessels run in the costal groove Posterior intercostal arteries 1st & 2nd - arise from superior/supreme intercostal artery (a branch of costocervical trunk of subclavian artery) 3rd -11th - branches of the thoracic aorta Accompanies intercostal nerve Accompany dorsal ramus to supply spinal cord, vertebrae, muscles and skin Anterior intercostal arteries 1st – 6th – from internal thoracic 7th- 9th – from musculophrenic 10th & 11th – have no anterior intercostal Anastomose with the posterior vessels in the intercostal spaces around the midclavicular line 4/10/2024

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27. Intercostal veins Anterior intercostal veins are tributaries of internal thoracic veins The posterior intercostal veins drain into azygos and hemiazygos system The superior veins drain into the brachiocephalic veins Right 1 st – right brachiocephalic vein 2 nd , 3 rd & 4 th - join to form superior intercostal which drain into azygos vein 5 th - 11 th & subcostal – drain to azygos vein Left 1st – left brachiocephalic vein 2 nd , 3 rd & 4 th – join to form superior intercostal which drain into left brachiocephalic 5 th - 8 th – drain into accessory hemiazygos vein 9 th - 11 th & subcostal – drain into hemiazygos vein 4/10/2024

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30. Lymph drainage Follows arteries of intercostal space Anterior vessels drain to parasternal lymph node (anterior IC node) Posterior vessels drain to paravertebral lymph node (posterior IC node) 4/10/2024

31. The Thoracic Cavity 4/10/2024

32. Thoracic cavity Cone shaped space enclosed by the thoracic walls Has narrow superior aperture (thoracic inlet) and wide inferior aperture (thoracic outlet) Thoracic cavity is divided into 3 divisions Two pleural cavities : occupy lateral part and contain the lungs The mediastinum : the space between lungs and pleurae The mediastinum contains the pericardium & the heart and associated great vessels trachea, esophagus, vagus nerves, phrenic nerves, thoracic duct, azygos veins, thymus, sympathetic trunk, etc 4/10/2024

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35. Pleurae and Lungs Pleurae Each lung is invested by a pleura The pleural has two parts The visceral pleura :- it is adherent to all surfaces of the lung. Insensitive to pain The parietal pleura :- lines the pulmonary cavities, adhering to the thoracic wall, the mediastinum, and the diaphragm The two layers are continuous around hilum A potential space between the two layers is called pleural cavity 4/10/2024

36. 1-Pleural Cavities Inferior margin = adjacent to T12 in Posterior Midline At Rib 10 at Midaxillary line At Rib 8 at Midclavicular line To Xiphosternal joint anteriorly Superior margin = transverse process of T1 posteriorly i.e. do not extend above rib 1 due to obliquity of thoracic inlet. Anterolateraly in cervix about 2.5 cm above clavicle 4/10/2024

37. Innervation and blood supply of the pleura Parietal pleura Cervical, costal and peripheral diaphragmatic portion - intercostal nerves and vessels Central portion of diaphragmatic and mediastinal – phrenic nerve and internal thoracic & musculophrenic vessels Sensitive to pain Venous drainage - intercostal veins, internal thoracic and azygos Lymphatics – intercostal, internal mammary, diaphragmatic & posterior mediastinal lymph nodes Visceral pleura Sympathetic nerves derived from T4 & T5 insensitive to pain vasculature and lymphatics are similar to lung 4/10/2024

38. Clinical correlates Pneumothorax – presence of air in the pleural cavity Haemothorax - when blood accumulates Hydrothorax - when fluid accumulates Pleurisy – inflammation of the pleura  rough surface  rubbing  sound 4/10/2024

39. Pleuricentesis (pleural tap) Aspiration of fluid from the pleural cavity Mostly done in the 6 th intercostal space at mid axillary line The needle should be inserted through middle part of intercostal space to avoid injury to neurovascular bundle 4/10/2024

40. LUNG The lungs are the vital organs of respiration Located in Pleural Compartments Lateral to Mediastinum Spongy in texture and pink in color in young but mottled black by carbon particles in adults 4/10/2024

41. LUNG Has : Apex = posterior to clavicle Three surface Diaphragmatic Costal Surface Mediastinal surface Three border Anterior, posterior & inferior border 4/10/2024

42. The base (diaphragmatic surface) Semilunar and concave Rests on diaphragm which separates the right lung from right lobe of liver and left lung from fundus of stomach It is found at the level of the 6 th costal cartilage in the mid-clavicular line the 8 th costal cartilage in the mid-axillary line rib 10 dorsally Due to the position of the liver, the base of the right lung is broader than that of the left lung 4/10/2024

43. Lungs: anterior view 4/10/2024

44. The root of the lung The root of the lung is formed by the structures entering and emerging from the lung at its hilum Lie at level of T5-T7 Pulmonary vessel Bronchopulmonary lymph nodes Bronchus Pulmonary plexus The hilum of the lung is the area on the medial surface of each lung. 4/10/2024

45. LUNG LOBES The righ t lung has three lobes , the left lung has two For right lung horizontal fissure divide superior and middle lobe and oblique fissure between middle and inferior lobes Left lung has a superior and inferior lobe divided by an oblique fissure The right lung is larger and heavier than the left, but it is shorter and wider because the right dome of the diaphragm is higher and the heart and pericardium bulge more to the left. 4/10/2024

46. LUNG The anterior margin of the right lung is relatively straight, whereas this margin of the left lung has a cardiac notch Examination of the superior lobe is done on the anterior chest wall, whereas examination of the inferior lobe is done posteriorly below the scapula 4/10/2024

47. Right lung Left lung Size Larger and heavier (700gm) Small and lighter (600gm) Length and width Shorter & broader Longer and narrower Anterior border Straight Cardiac notch & lingula Lobes and fissures Three lobes & two fissures Two lobes & one fissure Arterial supply One bronchial artery Two bronchial arteries Differences between right and left lung 4/10/2024

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51. Trachea and Bronchi The trachea bifurcate in to two main bronchi (primary bronchi), at the level of the sternal angle The right main bronchus is wider , shorter , and runs more vertically than the left main bronchus Inhaled particles tend to pass more frequently to the right lung 4/10/2024

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53. Bronchial Tree Primary (main) Bronchi Bifurcation of trachea at the level of T4 Cartilage plates replace rings Posterior to pulmonary vessels Right is wider, vertical, shorter Secondary (lobar) Bronchi Divisions of each primary bronchi Right lung has 3, Left has 2 Tertiary (segmental) Bronchi Up to 10 in each lung supply bronchopulmonary segments of the lung 4/10/2024

54. Bronchial Tree cont’ed Bronchioles Terminal Bronchioles Respiratory Bronchioles Alveolar Ducts Alveolar Sacs is Alveoli 4/10/2024

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56. Bronchopulmonary segments pyramidal section of a lung served with one tertiary bronchus base toward visceral pleura & apex toward hilum The right lung has 10 bronchopulmonary segments and the left lung has 9 Each segment is surrounded by connective tissue; independent respiratory units Limit the spread of some diseases within the lung, because infections do not easily cross the connective tissue partitions between them 4/10/2024

57. Bronchopulmonary segments 4/10/2024

58. Bronchopulmonary segments Right lung Upper Apical Anterior Posterior Middle Medial Lateral Lower Apical Anterior basal Posterior basal Medial basal Lateral basal Left lung Upper Apicoposterior Anterior Superior lingular Inferior lingular Lower Apical Anterior basal Posterior basal Medial basal Lateral basal 4/10/2024

59. Vasculature and Nerves of Lungs and Pleurae Each lung has a large pulmonary artery supplying blood to it and two pulmonary veins draining blood from it. 4/10/2024

60. Pulmonary artery Two in number; one for each lung derived from the bifurcated pulmonary trunk Carry poorly oxygenated blood to lungs for oxygenation divide into lobar branches and then tertiary branches 4/10/2024

61. Pulmonary veins Four in number; two for each lung Carry well-oxygenated blood Begin from pulmonary capillaries 4/10/2024

62. Bronchial Vasculature The bronchial arteries a single right bronchial artery normally arises from the third posterior intercostal artery two left bronchial arteries arise from thoracic aorta supply blood to the structures making up the root of the lungs, the supporting tissues of the lung, and the visceral pleura The bronchial veins drain into: either the pulmonary veins Or into the azygos vein on the right or into hemiazygos vein on the left Lymphatic are extensive and follow the vascular tree At the hilus of the lung, they are filtered by the pulmonary lymph nodes and then enter the right lymphatic duct , on the right side On the left side, lymph vessels enter the thoracic duct 4/10/2024

63. Nerves of the Lungs Supplied by bronchopulmonary plexus Parasympathetic fibers – from vagus motor to the smooth muscle of the bronchial tree ( bronchoconstrictor ) inhibitory to the pulmonary vessels ( vasodilator ) secretory to the glands of the bronchial tree ( secretomotor ). Sympathetic fibers - from T2-T5 vasomotor to arterial system ( vasoconstriction ) Bronchodilator Inhibitory to bronchial glands 4/10/2024

64. surface marking of the lung Lungs inferior margin is 2 ribs superior to pleural cavity (T10-posteriorly, rib 8 –mid axillary and rib 6- mid clavicle) Apex superior and posterior to the clavicles 4/10/2024

65. The Mediastinum between the two pleural sacs- Division Superior:- from superior thoracic aperture to sternal angle Thymus , great vessels , thoracic duct, trachea, esophagus, vagus nerves, left recurrent laryngeal nerve and phrenic nerves. Inferior :- from sternal angle to diaphragm Divided into anterior, middle and posterior 4/10/2024

66. Contents of superior mediastinum 4/10/2024

67. Mediastinum continued Inferior mediastinum Anterior mediastinum – b/n pericardial sac and sternum contains thymus, lymph nodes, fat, and connective tissue Middle mediastinum – occupied by pericardial sac, heart and roots of great vessels Posterior mediastinum –b/n lower eight thoracic vertebral bodies and pericardial sac , posterior portion of diaphragm inferiorly esophagus, thoracic aorta, azygos and hemiazygos veins, thoracic duct, vagus nerves & sympathetic trunks, 4/10/2024

68. Thymus The most anterior structure of the superior mediastinum Prominent in children, steadily grows until puberty (reach maximum size), after puberty involutes (fat and fibrous tissues) From lower part of the thyroid gland to the 4 th costal cartilage Has two lobes Site of proliferation of T-lymphocytes Arterial supply – inferior thyroid, internal thoracic, anterior intercostal Venous drainage – to left brachiocephalic, internal thoracic & anterior intercostal Lymphatics – parasternal, brachiocephalic & trachiobronchial Nerves – sympathetic – vasomotor 4/10/2024

69. Great blood vessels Brachiocephalic vein Formed by union of internal jugular vein and subclavian vein behind sternoclavicular joint Left brachiocephalic vein is t wo times longer than the right because it passes from the left to the right side Tributaries of BCV both right & left – internal thoracic vein, inferior thyroid vein Left only – left superior intercostal vein, thoracic duct Right only – right lymphatic duct 4/10/2024

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71. Superior vena cava (SVC) Formed by union of right and left brachiocephalic veins behind the right first costal cartilage near to the sternum Returns blood from all structures superior to the diaphragm, except the lungs and heart Ends at the level of the 3rd costal cartilag e, where it enters the right atrium 4/10/2024

72. Aorta Three parts – ascending aorta, arch of aorta & descending aorta Ascending aorta covered in the pericardium Begin behind left half of sternum at the level of 3 rd costal cartilage Ends at the level of right 2 nd costal cartilage The right and left coronary arteries arise 4/10/2024

73. Arch of aorta Begin in the right 2 nd costal cartilage , directs upward, back ward and to the left Ends at the lower border of T4 to be continuous with the descending aorta Branches Brachiocephalic trunk Left common carotid left subclavian 4/10/2024

74. Thoracic aorta Continuation of arch of aorta Branches Posterior intercostal Subcostal Phrenic arteries Esophageal Bronchial Pericardial 4/10/2024

75. Trachea Begins below the larynx (cricoid cartilage) at the level of C6 About 10 cm long and 2.5 cm wide Partly in the neck and partly in the superior mediastinum bifurcates at the level of T4/5 (sternal angle) lies in the median plane and inferiorly it is displaced to the right by the aortic arch 4/10/2024

76. Neurovasculature Blood supply - branches from inferior thyroid artery & bronchial artery Venous drainage – left brachiocephalic through inferior thyroid vein Lymphatic – pretracheal and paratracheal lymph nodes Nerve supply Parasympathetic - vagus through recurrent laryngeal nerve; secretomotor to glands and bronchoconstrictors Sympathetic trunk – bronchodilator and vasoconstrictors 4/10/2024

77. Phrenic nerve Got branch from cervical plexus Root - ventral rami of C3, C4 & C5 Mixed nerve Motor - to diaphragm Sensory – to fibrous and parietal layer of serous pericardium, mediastinal & diaphragmatic pleura, diaphragmatic peritoneum & abdominal viscera (liver, gall bladder & suprarenal gland) 4/10/2024

78. Vagus nerve The tenth cranial nerve originating from medulla oblongata Enters superior mediastinum posterior to sternoclavicular joint and brachiocephalic vein gives rise to recurrent laryngeal nerve and continues into abdomen Give branch to pulmonary plexus, esophageal plexus , and cardiac plexus Recurrent laryngeal nerve innervate trachea , esophagus and larynx 4/10/2024

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80. Middle mediastinum Boundary superior - imaginary line Inferior- diaphragm Right and left lateral – corresponding Mediastinal surfaces of pleura Anterior – anterior mediastinum and part of pleura Posterior – posterior mediastinum Contents The heart and the pericardium Great vessels – SVC, IVC, Pulmonary trunk & veins, part of aorta, parts of the phrenic nerve 4/10/2024

81. Pericardium A double-walled fibroserous sac that encloses the heart and roots of great vessels Parts: two fibrous pericardium The loose fitting outer layer of the sac This tough, dense connective tissue layer protects the heart; anchors the heart; and prevents sudden overfilling Serous pericardium Internal double-layered serous membrane a closed sac sandwiched between the fibrous pericardium and the heart Has two layers are Parietal layer Visceral layer The pericardial cavity is the potential space between parietal and visceral layers . It contains a thin film of serous fluid that enables the heart to move and beat in a frictionless environment 4/10/2024

82. Blood supply and innervation Fibrous and Parietal pericardium Arteries – pericardiophrenic (main), musculophrenic art. Veins – to pericardiophrenic & azygos vein Nerve – phrenic; sensitive to pain Visceral pericardium Artery – coronary Vein – coronary Nerve – autonomic nerves of heart; not sensitive to pain 4/10/2024

83. Clinical correlates Pericarditis - i nflammation of the pericardium hinders production of serous fluid causing the heart to rub Cardiac tamponade - inflammatory fluid seep into the pericardial cavity since fibrous pericardium is tough and inelastic it compress the heart and limit its ability to pump blood Pericardial effusion – collection of fluid in pericardial cavity Pericardiocentesis - removal of fluid puncture is at left 5 th /6 th intercostal space or between xiphoid process and left side of infrasternal angle, needle inserted superoposteriorly 4/10/2024

84. The Heart The heart is a muscular pumping organ with two functions:- Its right side receives oxygen poor blood from the body tissues and then pumps it to the lungs Its left side receives oxygenated blood from the lungs and then pumps it to the body 4/10/2024

85. Size, location and position of heart The heart is about the size of a fist It weighs between 250 - 350 grams Located in the middle mediastinum, anterior to the vertebral column & posterior to the sternum It extends from the 2 nd rib to 5 th intercostal space Two thirds of the heart lies to the left of the mid- sternal line 4/10/2024

86. Heart Chambers The heart has four chambers Two atria Two ventricles The atria lie above and behind ventricles Upper part of each atrium has an appendage called auricle The chambers are separated by Interatrial septum Interventricular septum Atria Ventricles Septum 4/10/2024

87. Heart cont’ed Shape 3 sided pyramid with apex, base and 4 borders and 4 surfaces The apex lies in left 5th intercostal space just medial to midclavicular line formed by left ventricle The base At vertebral levels of T6 –T9 Forms the posterior surface Formed mainly by left atrium and small part of right atrium 4/10/2024

88. Heart cont’ed Borders Right – formed by right atrium Left –formed mainly by left ventricle and partly by left auricle Inferior – formed mainly by right ventricle Superior – formed by two atria 4/10/2024

89. Surfaces Diaphragmatic (inferior) surface Rests on central tendon of diaphragm formed by left ventricle (left 2/3) and right ventricle (right 1/3) Sternocostal (anterior) surface Formed mainly by right atrium and right ventricle; and partly by left ventricle and left auricle Pulmonary surface Formed by left and right ventricle 4/10/2024

90. Right atrium Receives venous blood from the body through SVC, IVC and coronary sinus and pumps it to right ventricle Upper end is prolonged to left to form right auricles Sulcus terminalis - a shallow groove along right border run from SVC to IVC vertically Produced by internal muscular elevation ( cristae terminalis ) Upper end is land mark of SA node IVC 4/10/2024

91. Right atrium: internal features The interior of the right atrium is divided into two continuous spaces. The smooth posterior part (sinus venarum ) SVC & IVC opens into it Coronary sinus opens between IVC orifice and right AV orifice The rough anterior part ( pectinate part) A series pectinate muscles Arise from crista terminalis and run towards AV orifice 4/10/2024

92. Right atrium: internal features The Interatrial septum Separate the atria Presents, fossa ovalis Remnant of foramen ovale of the fetal heart limbus fossa ovalis a prominent margin of fossa ovalis 4/10/2024

93. Right ventricle Receive blood from right atrium and pump into pulmonary trunk Superiorly tapers into a cone, conus arteriosus (infundibulum) Internal structure Outflow part – smooth, pulmonary trunk arise, separated from inflow part by supraventricular crest Inflow part – rough due to muscular ridges called trabeculae carneae 4/10/2024

94. Right ventricle Papillary muscles Conical projections arise from ventricular wall whose free ends are for chordae tendineae Three: anterior, posterior & septal Contract before contraction of ventricle, tightening tendinous cords and drawing cusps together 4/10/2024

95. Interventricular septum Partition between ventricles Composed of membranous and muscular parts Membranous – superoposterior , thin, continuous with fibrous skeleton Muscular part – thick, bulges to the right 4/10/2024

96. Septo marginal band (moderator band) Muscular bundle runs from interventricular septum to base of anterior papillary muscle Carries part of the right bundle of the AV bundle of conducting system Facilitate conduction time allowing contraction of the papillary muscle before contraction of ventricle wall 4/10/2024

97. Left atrium Blood enters the left atrium via four veins 2 Right and 2 left pulmonary veins Thicker than right Interior large smooth part and small muscular part pectinate muscles are found in the auricle Left pulmonary veins 4/10/2024

98. Posterior aspect of heart 4/10/2024

99. Left Ventricle Receive blood from left atrium & pumps into the aorta The walls of the left ventricle are 2-3 times thicker than that of the right ventricle Due to the work load 4/10/2024

100. Internal structure The cavity is circular and longer than the right smooth upper part and rough lower part trabeculae carneae are finer and more numerous than the right Papillary muscles: two; anterior and posterior Smooth walled posterosuperior part – aortic vestibule, leads to aortic orifice Left Ventricle: Internal structure 4/10/2024

101. Heart Valves Heart valves maintain a one-way flow of blood Type:- two main type Atrioventricular Semilunar Valves open and close in response to differences in blood pressure Bicuspid (mitral) valve Tricuspid valve Aortic valve Pulmonary valve 4/10/2024

102. Heart Valves 4/10/2024

103. Atrioventricular (AV) Valves located at each atrio -ventricular junction The right AV valve (tricuspid ) has three flexible cusps - anterior, posterior & septal The left AV valve (bicuspid) has two flexible cusps - anterior and posterior The cusps are flaps of endocardium reinforced by connective tissue Attached to each of the AV valve flaps are tiny cords called chordae tendinae The cords anchor the cusps to the papillary muscles 4/10/2024

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105. Components of the AV valve Fibrous ring – part of the fibrous skeleton of the heart surrounding AV orifice; resist dilation Cusps – projection of the endocardium has attached (to fibrous ring) and free border two surfaces atrial – smooth ventricular – rough Chordae tendineae - connect the free ventricular ends of cusps with the apex of papillary muscles Prevents separation and inversion of the cusps during systole Papillary muscles – projection of the myocardium of the ventricle 4/10/2024

106. The AV valve Blood flows into the atria & then through the open AV valves into the ventricles When the atria contract, force additional blood into the ventricles through open AV valve When the ventricles begin to contract, intra- ventricular pressure rises forcing blood superiorly against the valve flaps The chordae tendonae and the papillary muscles anchor the flaps in their closed position 4/10/2024

107. Semilunar (SL) Valves Found at the bases of the large arteries exiting the ventricles The aortic and pulmonary semilunar valves pulmonary valve is B/n pulmonary trunk into the right ventricle . aortic valve - B/n aorta and the left ventricle Each semilunar valve is made up of three pocket like cusps Anterior/posterior, right & left Concave superiorly Spaces between dilated wall of the vessel and each cusp – sinuses (pulmonary & aortic) Blood in sinuses prevents cusps from sticking to wall of the vessel 4/10/2024

108. Semilunar (SL) Valves 4/10/2024

109. Heart Sounds The closing of the heart valves causes vibrations in the adjacent blood and heart walls that account for the familiar “ lub -dub” sounds of the heartbeat The “ lub ” is produced by the closing of the AV valves at ventricle contract The “dup” is produced by the closing of the semilunar valves at ventricle relax Sounds are heard away from the valves in the direction of the blood flow 4/10/2024

110. Surface markings of the valves and auscultation areas Valve (diameter) Surface marking auscultation area Pulmonary (2.5 cm) Upper border of 3 rd left costal cart. near sternum sternal end of 2 nd right intercostal space Aortic (2.5 cm) Behind left half of sternum at the level of medial end of 3 rd intercostal space Sternal end of 2 nd right intercostal space Mitral (3 cm) Behind the left half of sternum opposite to 4 th costal cartilage 5 th left intercostal space (cardiac apex) at midclavicular line Tricuspid (4 cm) Behind the right half of sternum opposite to 4 th and 5 th intercostal space 5 th right intercostal space near sternal body 4/10/2024

111. Surface markings of the valves and auscultation areas 4/10/2024

112. Fibrous Skeleton of the heart Is a complex framework of dense collagen forming four fibrous rings that surround the orifices of the valves Lies in the plane between the atria and the ventricles surrounding the four valves Composed of dense connective tissue Function Anchors the valve cusps Prevents over dilation of the valve openings Insertion for the bundles of cardiac muscle in the atria and ventricles Blocks the direct spread of electrical impulses from the atria to the ventricles 4/10/2024

113. Layers of the Heart Wall The heart wall is composed of three layers (superficial to deep) Epicardium Myocardium Endocardium All three layers are richly supplied with blood vessels Epicardium – outer layer is the visceral layer of the serous pericardium often infiltrated with fat, especially in older people Myocardium – middle layer Layer of cardiac muscle forming the bulk of the heart Elongated, circularly and spirally arranged muscle cells squeeze the blood though the heart 4/10/2024

114. The endocardium – inner layer Is a glistening white sheet of endothelium (squamous epithelium) resting on a thin layer of connective tissue Located on the inner myocardial surface, it lines the heart chambers and covers the connective tissue skeleton of the valves The endocardium is continuous with the endothelial linings of the blood vessels leaving and entering the heart 4/10/2024

115. Conducting System of the Heart Contains specialized cardiac muscle cells and highly specialized conducting fibers coordinates the cardiac cycle 4/10/2024

116. The components of the conducting system Sinoatrial (SA) node Location:-below the entrance of the SVC Initiates and regulates the impulses for contraction The heart’s own pacemaker generate 70-80 impulses per minute Atrioventricular (AV) node Located in the interatrial septum near the opening of the coronary sinus Transmit action potential to the atrioventricular AV) bundle 4/10/2024

117. Atrioventricular bundle (AV bundle):- The only pathway for impulses from the atria to the ventricles, Also called the bundle of His . Located in upper interventricular septum It transmits impulses to the right and left bundle branches Purkinje fibers:- Transmit impulses to the papillary muscles and walls of the ventricles 4/10/2024

118. Blood supply of the heart Arterial supply Coronary aa Supply myocardium and epicardium of the heart, The endocardium receives oxygen and nutrients directly from the chambers of the heart. Arise from ascending aorta Right coronary artery:- branches posterior IV branch SA & AV nodal branch right marginal branch Left coronary artery:- branches anterior IV branch SA nodal branch circumflex branch Left marginal branch 4/10/2024

119. Right coronary artery supplies The whole of right atrium Most of the right ventricle Part of left ventricle (diaphragmatic surface) Part of interventricular septum (posterior third) SA node (in 60% of people) AV node (in 80% of people) 4/10/2024

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121. Left coronary artery supplies The left atrium Most of the left ventricle Part of right ventricle Most of interventricular septum (anterior two third) SA node (in 40% of people) 4/10/2024

122. Veins of the heart the heart is drained mainly by veins that drain into coronary sinus which empties into the right atrium Coronary sinus It receives Great cardiac vein Middle cardiac vein Small cardiac vein Oblique vein Left posterior ventricular vein Left marginal vein Anterior cardiac vein from the anterior aspect of right atrium empty directly to right atrium Smallest cardiac veins ( venae cordis minimae ) begin in myocardium and open directly into all chambers 4/10/2024

123. Coronary veins 4/10/2024

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125. Innervation of the heart Although the heart’s inherent rate of contraction is set by the SA node , this rate can be altered by extrinsic neural controls Parasympathetic nerve supply From Vagus nerve Parasympathetic stimulation slows the heart rate, reduces force of contraction and constricts coronary arteries Sympathetic nerves from the cervical and upper thoracic sympathetic trunks Sympathetic stimulation increases the rate and force of heart contractions and produce dilation of coronary arteries 4/10/2024

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127. Posterior mediastinum A space behind the pericardium and diaphragm Boundaries Posteriorly – thoracic vertebrae ( T5- T12) Anteriorly pericardium and diaphragm 4/10/2024

128. Contents Esophagus Descending thoracic aorta and its branches Thoracic duct Azygos system of veins Thoracic sympathetic trunk and splanchnic nerves Vagus nerve 4/10/2024

129. Contents 4/10/2024

130. The azygos & Hemiazygos venous systems Azygos vein Drain the posterior thoracic wall and upper lumbar region Connects superior and inferior venae cavae Formation Originate in the abdomen by union of lumbar azygos, right ascending lumbar and right subcostal veins Course Enter thoracic cavity through aortic opening or pierce right crus of diaphragm Ascends on the right side of the vertebral column and arches over the right bronchus to enter the posterior aspect of the SVC at the level of T 4 4/10/2024

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132. Tributaries Right superior intercostal vein Right 4 – 11 intercostal veins Right subcostal vein and right ascending lumbar Right bronchial vein Esophageal, Mediastinal & pericardial veins Hemiazygos vein Accessory hemiazygos vein 4/10/2024

133. Hemiazygos vein Origin In the abdomen by union of left ascending lumbar and left subcostal or from left renal vein Course Enter thoracic cavity piercing the left crus of diaphragm  at T 9 crosses to the right behind thoracic aorta, esophagus & thoracic duct  end in azygos vein Tributaries 9th – 11th left intercostal Left subcostal Left ascending lumbar 4/10/2024

134. The azygos and hemiazygos venous systems 4/10/2024

135. Accessory Hemiazygos vein Originate at medial end of 4 th and 5 th intercostal space on the left of the vertebral column Crosses to the right at T8 behind aorta, esophagus and join azygos vein Tributaries Left 5 th - 8 th intercostal veins Left bronchial vein 4/10/2024

136. The azygos and hemiazygos venous systems 4/10/2024

137. Esophagus Muscular tube, food passage between pharynx and stomach extends from the level of C6 to the stomach (T11), below the left dome of the diaphragm (25cm) Three parts – cervical, thoracic & abdominal Pierces the diaphragm at the level of the rib 7 costal cartilage (T 10 ) 4/10/2024

138. Esophagus Constrictions - in 4 regions C6 (at beginning) T2/3 (crossing of aortic arch) T4/5 (crossing of left primary bronchus) T10 (diaphragm) Obstructions may occur at these levels. These levels are respectively 15, 22, 27 and 40 cm from the incisor teeth 4/10/2024

139. Sphincters superior esophageal sphincter - at junction with pharynx ;voluntary inferior esophageal sphincter – at junction with stomach; under the control of vagal (opener) and sympathetic fibers (closer) 4/10/2024

140. Blood supply of Esophagus Arterial supply Cervical part up to arch of aorta – inferior thyroid arteries Thoracic part – esophageal branches of thoracic aorta Abdominal part – esophageal branches of left gastric artery Venous drainage Upper part – brachiocephalic veins Middle part – azygos veins( systemic vein) Lower end – left gastric vein (portal drainage) Lower end of esophagus is one of the sites of anastomosis between systemic and portal veins  porto -systemic anastomosis In portal hypertension, dilation of lower esophageal veins called esophageal varicose  rapture of these veins result in vomiting of blood 4/10/2024

141. Nerve supply -autonomic Parasympathetic Upper ½ - recurrent laryngeal nerve Lower ½- esophageal plexus (formed by the two vagi ) Function – sensory, motor to muscles and mucus secreting glands Sympathetic upper ½ - middle cervical ganglion Lower ½- upper 4 thoracic ganglia (esophageal plexus) Function – vasomotor Lymphatic drainage Cervical – deep cervical lymph nodes Thoracic- posterior mediastinal lymph nodes Abdominal – left gastric lymph nodes 4/10/2024

142. The thoracic duct Largest lymphatic vessel Begins at the cisterna chyli (L 1 ), posterior to the abdominal aorta, inferior to the diaphragm Enters the thorax through aortic opening posterior to the aorta Ascends on the right of the vertebral column At T5 cross to left side 4/10/2024

143. The thoracic duct In the root of the neck it arches laterally (C7) terminate at the junction between the left subclavian and left internal jugular veins 4/10/2024

144. Tributaries of thoracic duct Posterior mediastinal nodes Intercostal nodes Left jugular trunk Left subclavian trunk Left mediastinal trunk It drains all the lymph of the body except for the right thorax, right upper limb and right side of the head and neck These remaining areas drain into the right lymphatic duct which joins the junction of the right internal jugular and right subclavian veins 4/10/2024

145. Thoracic duct draining into brachiocephalic V Thoracic duct Cistrena chyli Accessory Azygos Hemiazygos Azygos Intercostal lymph nodes Right lymphatic duct 4/10/2024

146. The thoracic duct 4/10/2024

147. Sympathetic trunk Is gaglionated chain on each side of the thoracic vertebral column Continues superiorly with cervical sympathetic chain inferiorly with lumbar chain Contain 12 ganglia, but often 10 or 11 due to fusion of adjacent ganglia The ganglia are connected to adjacent thoracic spinal nerves by white and gray rami communicantes and are numbered according to the thoracic spinal nerve with which they are associated. The first is commonly fused with inferior cervical ganglion to form cervicothoracic or stellate ganglion Lie at levels of corresponding intervertebral discs and intercostal nerves 4/10/2024

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150. Branches - two groups Lateral branches – for limbs & body wall Communicate with spinal nerve by two rami White ramus – from spinal nerve to the ganglia ( preganglionic fiber) Grey ramus - from ganglia to spinal nerves (postganglionic fibers) Function Piloerection – arrector pili muscle of skin Vasomotor – blood vessels Secretomotor – sweat glands 4/10/2024

151. Medial branches – to thoracic and abdominal viscera Upper five ganglia – supply Heart – cardiac plexus Great vessels – aortic plexus Lung – pulmonary plexus Esophagus – esophageal plexus Lower seven ganglia – from three splachnic nerves which supply abdominal viscera Greater splanchnic – 5 th – 9 th ; ends in coeliac , aorticorenal or suprarenal Lesser splanchnic – 10 th & 11 th ; ends in coeliac ganglion Lowest (least ) splanchnic – 12 th ; ends in renal plexus 4/10/2024

152. Diaphragm Dome-shaped musculotendinous partition between thoracic and abdominal cavities Principal muscle of respiration Composed of two portions: muscular (peripheral part) and aponeurotic ( central part) Muscular part Fibers converge radially to central tendon 3 parts based on origin Sternal – back of xiphoid process Costal – inner surface of lower six costal cartilage Vertebral –lumbar vertebrae by two crura Right – superior 3 Left – superior 2 Crura are united superiorly at T12 by narrow arch called median arcuate ligament 4/10/2024

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154. Diaphragm Central tendon Aponeurotic tendon formed by fibers of different direction Has three lobes (right, left & median) 4/10/2024

155. Major openings Aortic – T 12 median plane, transmits descending aorta, thoracic duct, azygos vein Esophageal – T 10 left of the median plane, transmits esophagus, vagi (anterior & posterior), esophageal branch of left gastric artery Vena caval - – T 8 right of the median plane with in the central tendon, transmits IVC, branch of right phrenic, lymph vessels from liver 4/10/2024

156. Other structures passing through diaphragm Superior epigastric vessels – b/n sternal & costal origins Musculophrenic nerve– pierce at 7 or 8 costal cartilage Lower five intercostal nerves - b/n two slips of costal origin Subcostal nerves and vessels - behind lateral arcuate ligament Quadratus lumborum - behind lateral arcuate ligament Sympathetic trunk - behind medial arcuate ligament Psoas major – behind medial arcuate ligament Splanchnic nerves – pierce the corresponding crus of diaphragm Hemiazygos vein - pierce the left crus of diaphragm 4/10/2024

157. Nerve supply : Phrenic (motor and sensory) lower six intercostal and sub costal for peripheral part (sensory) Blood supply: Arteries Superior surface Superior phrenic (thoracic aorta) Musculophrenic and pericardiophrenic (internal thoracic artery) Inferior surface: inferior phrenic( abd aorta) Veins : same Lymphatic drainage Thoracic surface to phrenic nodes Abdominal surface to lateral aortic nodes The two surfaces communicate freely 4/10/2024

158. Thank You 4/10/2024