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THORACIC CAVITY

THORACIC CAVITY. HEART. Pericardial Cavity. Heart is located in the middle inferior mediastinum within the pericardial cavity. Visceral Pericardium. Serous membrane Fig 1.37, p 139) Referred to as epicardium. Arterial mesocardium. Venous mesocardium. Visceral Pericardium.

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THORACIC CAVITY

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  1. THORACIC CAVITY HEART

  2. Pericardial Cavity • Heart is located in the middle inferior mediastinum within the pericardial cavity.

  3. Visceral Pericardium • Serous membrane • Fig 1.37, p 139) • Referred to as epicardium. • Arterial mesocardium. • Venous mesocardium.

  4. Visceral Pericardium • Transverse sinus: Space between arterial and venous mesocardium. • Oblique sinus: Space between right and left pulmonary veins.

  5. Pericardium • Pericardial cavity. • Parietal (serous): Fused to fibrous pericardium. • Fibrous: Fused with central tendon of diaphragm: Pericardiacophrenic ligament. Fused with sternum: Superior and inferior sternopericardial ligaments.

  6. Pericardium • Blood supply (Fig. 1.38, p 139): Pericardial arteries. Pericardiacophrenic arteries. Musculophrenic arteries. • Nerve supply: CN X. Phrenic nerve. Sympathetic trunk.

  7. Cardiac Projections • Apex is down and to left. • Base of heart is superior to apex: Upside down triangle. • Base projection: Horizontal plane across sternum. Level of costal cartilage 3. Ends 2 cm to left of left parasternal line.

  8. Cardiac Projections • Apex projection: 5th intercostal space. 8 cm (interclavicular line) to left of median line of sternum. • Pericardium extends up to sternal angle.

  9. Layers of the Heart • External: Epicardium Visceral layer of serous pericardium + subserous layer of connective tissue. • Middle: Myocardium: Thickest Cardiac muscle tissue.

  10. Layers of the Heart • Inner: Endocardium: Endothelial layer

  11. Cardiac Skeleton • 4 interlocking fibrous rings: Annuli fibrosi. Interconnected with membranous portion of interventricular septum. • Fig. 1.40B, p 143)

  12. Cardiac Skeleton • Functions of annuli fibrosi: Rigid attachment for cardiac muscle fibers. Support for valves.

  13. External Heart • Base: Posterior aspect of heart. Mostly left atrium + small part of right atrium. • Apex: Located at intercostal space 5 medial to nipple. Formed from left ventricle • Fig. 1.42A, p 146.

  14. External Heart • Diaphragmatic surface: Rests on diaphragm. Mostly left ventricle and a small part of right. • Sternocostal surface: Faces anteriorly. Mostly right ventricle.

  15. External Heart • Left margin (border): Left side of heart formed mostly of left ventricle and left auricle. • Inferior margin (border): Intersection of diaphragmatic and sternocostal surfaces. Formed mostly from right ventricle. • Superior border: Left and right atria and auricles.

  16. Anterior Surface of Heart CC: common carotid A. AA: aortic arch SC: subclavian V. SVC: sup. VC RPA: right pulmonary artery. RPV: right pulmonary veins. RCA: right coronary A. IVC: inferior vena cava. LA: ligamentum arteriosum

  17. Anterior Surface of Heart LPA: left pulmonary A. LPV: left pulmonary V. CB: circumflex branch of left coronary A. LM: left marginal A. LAD: left anterior descending A.

  18. Blood Supply to Heart • Blood supply to heart is via two coronary arteries (Fig. 1.49A&B, 157): Coronary arteries are the direct and only branches off the ascending aorta.

  19. Right Coronary Artery • Passes between pulmonary trunk and right auricle. • To coronary sulcus. • Follows coronary sulcus to diaphragmatic surface. • Anastomoses with left coronary artery.

  20. Right Coronary Artery Supplies: • Right atrium. • Right ventricle. • Posterior half of interventricular septum.

  21. Right Coronary Artery Branches • Artery to SA node. • Artery to AV node. • Right marginal artery. • Posterior interventricular artery = posterior descending artery (PDA)

  22. Left Coronary Artery • Passes between pulmonary trunk and left atrium. • Supplies: Left atrium. Left ventricle. Anterior half of interventricular septum.

  23. Left Coronary Artery • Major branches: Anterior interventricular artery (= left anterior descending LAD). Circumflex artery. Left marginal artery.

  24. Venous Drainage from Heart • Fig. 1.51, page 159 • Coronary sinus: Located in posterior coronary sulcus. Opens into right atrium. Direct continuation of great cardiac vein. Tributaries: Great cardiac vein. Middle cardiac vein. Small cardiac vein.

  25. Right Atrium • Fig. 1.43, p 148: • Receives blood from: Superior vena cava. Inferior vena cava. Coronary sinus. Anterior cardiac veins. • Large, thin-walled chamber.

  26. Right Atrium • Sub-chambers: Main posterior cavity: Sinus venarum. Anterior cavity: Auricle. Lined with pectinate muscles.

  27. Right Ventricle • Fig. 1.44, p 149 • Receives blood from right atrium. • Thicker walled than right atrium. • Trabeculae carnae. • Moderator band: (septomarginal trabecula) Conveys right branch of atrioventricular bundle.

  28. Right Atrioventricular Valve • Also called the tricuspid valve. • Chordae tendinae. • Papillary muscles. • Fig. 1.45 B&C, p 150

  29. Right Ventricle • Pulmonary valve: Formed from three semilunar cusps. • Pulmonary trunk: Divides into left and right pulmonary arteries.

  30. Left Atrium • Left atrium (Fig. 1.46, p 152): Receives blood from four pulmonary veins. Smaller and thicker-walled than right atrium. Posterior smooth portion receives pulmonary veins. Anterior portion = auricle: with pectinate muscles.

  31. Left Ventricle • Fig. 1.47, p 153 • Wall = 2-3 x as thick as wall of right ventricle. • Trabeculae carnae are less coarse than those of right ventricle. • No moderator band. • Two large papillary muscles: Anterior and posterior.

  32. Left Atrioventricular/Aortic Valves • Left atrioventricular valve: = bicuspid or mitral valve. • Aortic valve: Composed of three semilunar cusps.

  33. Conduction System of the Heart • Composed of modified specialized cardiac muscle cells. • No nervous tissue in heart. • Fig. 1.52, p 163)

  34. Sinoatrial Node • Referred to as pacemaker of heart. • Located in right atrium near opening of SVC: Superior end of sulcus terminalis. • Receives direct stimulation from: Sympathetic cardiac nerves. Parasympathetic vagus nerves.

  35. Conduction System of the Heart • Atrioventricular node: Located in interatrial septum near tricuspid valve. • Interventricular bundle: Descends through channel in fibrous skeleton. Reaches membranous interventricular septum. Only connection between myocardium of atria and that of ventricles.

  36. Conduction System of the Heart • Interventricular bundle: Divides into two bundles in membranous portion: Right crus (bundle branches) passes through moderator band. Left crus (bundle branches)

  37. Conduction System of the Heart • Purkinje fibers: Terminal endings of bundle fibers. Embedded in myocardium of ventricle.

  38. Great Vessels • Ascending aorta: Runs behind sternum to sternal angle. Only branches are the two coronary arteries. • Fig. 1.58, p 172

  39. Arch of the Aorta • Lies within superior mediastinum. Arches to the left over the left pulmonary artery. • Apex of the arch reaches the middle of the manubrium. • Three main branches: Brachiocephalic. Left common carotid. Left subclavian.

  40. Arch of the Aorta • Anterior relationships: Left phrenic nerve. Left vagus nerve. Superficial cardiac plexus.

  41. Arch of the Aorta • Inferior relationships: Left recurrent laryngeal nerve. Ligamentum arteriosum. Pulmonary trunk. Left primary bronchus.

  42. Arch of the Aorta • Posterior relationships: Trachea Left recurrent laryngeal nerve.

  43. Descending Aorta • Lies within posterior mediastinum. • Begins at level of sternal angle. • Ends in front of thoracic vertebra 12. • Continuous with abdominal aorta.

  44. Descending Aorta Branches • Paired intercostal arteries. • Paired subcostal arteries. • Two or more bronchial arteries. • Two to five esophageal arteries.

  45. Other Thoracic Vessels • Supreme intercostal: From costocervical trunk of subclavian artery. Supplies IC spaces one and two. • Internal thoracics: Arise within root of neck. Descend lateral to sternum.

  46. Internal Thoracic Arteries • Branches: Musculophrenic (terminal): To diaphragm To intercostal spaces 7-9 Superior epigastric (terminal)

  47. Internal Thoracic Arteries • Branches: Pericardioacophrenic arteries: Accompanies phrenic nerve. Supplies pericardium, mediastinal pleura, diaphragm. Perforating branches: Accompany anterior cutaneous branches of intercostal nerves. Largest in intercostal spaces 2-4 in females.

  48. Right Brachiocephalic Vein • From: Right internal jugular. Right subclavian. • Tributary: Right internal intercostal vein. • Fig. 1.64, p 182

  49. Left Brachiocephalic Vein • Formed from: Left internal jugular vein. Left subclavian vein. • Tributaries: Left internal thoracic vein. Left superior intercostal. Inferior thyroid veins.

  50. Superior Vena Cava • Formed from: Right brachiocephalic vein. Left brachiocephalic vein. • Receives: Azygos vein.

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