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 Transverse sinus: Oblique sinus: Space between arterial and venous mesocardium. Oblique sinus: Space between right and left pulmonary veins.

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

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

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.

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

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

Layers of the Heart Inner: Endocardium: Endothelial layer

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

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

External Heart Base: Apex: Fig. 1.42A, p 146. 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.

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

External Heart Left margin (border): Inferior 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.

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

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.

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.

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

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

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

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

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

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.

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.

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

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.

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

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

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.

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.

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

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

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.

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.

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)

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

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

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.

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

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

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

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

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

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.

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

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.

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

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

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

Azygos System Drains most of blood from thoracic wall. Consists of longitudinal veins lying on either side of thoracic vertebral bodies. Variable.

Azygos Vein Forms in abdomen: From right subcostal and ascending lumbar veins. Drains all right posterior intercostal veins except first. Also receives blood from the bronchial and esophageal veins.

Hemiazygos Vein From left subcostal and left ascending lumbar veins. Forms in abdomen: From left subcostal and left ascending lumbar veins. Receives four posterior intercostal veins. Crosses over thoracic vertebrae at T8 level. Empties into azygos vein.

Other Thoracic Vessels Accessory hemiazygos vein: Drains intercostal spaces 4-7(8) on left side. Crosses over thoracic vertebrae at level T7. Empties into azygos vein. Note: Intercostal space 1 is drained by the supreme intercostal vein emptying into the brachiocephalic vein.