Pericardial Cavity & Sinuses

Home , Ascending aorta, Moderator band (heart), Pericardium

1 OUTLINE

• MIDDLE MEDIASTINAL SURFACE ANATOMY • PERICARDIUM • THE HEART • GREAT VESSELS

2 Learning objective

• By the end of this lecture, students should be able to: • Know the cardiac surface anatomy and their anatomical relations. • Know the pericardium anatomy and their relations . • Know the anatomy of the heart, anatomical relations and their differences. • Have the knowledge of heart skeleton and their anatomical relations. • Have deep understanding of the great vessels and their clinical importance

INTRODUCTION

• Middle mediastinum includes: -pericardium -Heart -roots of its great vessels: ascending aorta, pulmonary trunk, and SVC—passing to and from the heart

5 SURFACE ANATOMY OF FOUR CARDIAC ORIFICES

6 PERICARDIUM

• Pericardium consists of an outer fibrous sac lined with an inner serous sac. • The heart and the roots of the great vessels lie inside the fibrous sac and invaginate the serous sac from behind. • Fibrous pericardium is strong, dense and blend with the central the central tendon of the diaphragm • The ascending aorta carries the pericardium upward beyond the heart to the level of the sternal angle. • Serous pericardium consists of the parietal layer, which lines the inner surface of the fibrous pericardium, and the visceral layer, which forms the outer layer (epicardium) of the heart wall and the roots of the great vessels. 7 PERICARDIUM

8 PERICARDIAL CAVITY & SINUSES

Pericardial Cavity • Is a potential space between the visceral layer of the serous pericardium (epicardium) and the parietal layer of the serous pericardium lining the inner surfaces of the fibrous pericardium.

Pericardial Sinuses Transverse Sinus • Is a subdivision of the pericardial sac, lying posterior to the ascending aorta and pulmonary trunk, anterior to the SVC, and superior to the left atrium and the pulmonary veins. • Is of great importance to the cardiac surgeon because while performing surgery on the aorta or pulmonary artery, making a ligature through the sinus between the arteries and veins, thus stopping the blood circulation with the ligature. Oblique Sinus • Is a subdivision of the pericardial sac behind the heart, surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferior vena cava (IVC).

9 10 PERICARDIUM- ARTERIAL SUPPLY

• Main arterial supply of the pericardium is from pericardiacophrenic artery, a slender branch of the internal thoracic artery, • Smaller contributions from : -Musculophrenic artery, a terminal branch of the internal thoracic artery. -Bronchial, esophageal, and superior phrenic arteries, branches of the thoracic aorta. -Coronary arteries (visceral layer of serous pericardium only), the first branches of the aorta.

11 PERICARDIUM- VENOUS & NERVE SUPPLY Venous drainage of the pericardium: • Pericardiacophrenic veins, tributaries of the brachiocephalic (or internal thoracic) veins. • Variable tributaries of the azygos venous system Nerve supply of the pericardium: • Phrenic nerves (C3–C5) • Vagus nerves • Sympathetic trunks

12 HEART

• It is a muscular pump somewhat larger than a closed fist. • It has four chambers: right and left atria and right and left ventricles • Atria are separated from the ventricles by a constriction that completely the heart called coronary(atrioventricular) sulcus. • Ventricles are separated from each other by the anterior & posterior interventricular(longitudinal) sulci • Heart has 3 surfaces Stenocostal (anterior) Diaphragmatic (inferior) Base (posterior) • It also has an apex- lowest & leftmost point • The wall consists of three layers: inner endocardium, middle myocardium, and outer epicardium. • The sulcus terminalis, a groove on the external surface of the right atrium, marks the junction of the primitive sinus venosus with the atrium in the embryo and corresponds to a ridge on the internal heart surface, the crista terminalis

13 SURFACE ANATOMY OF FOUR CARDIAC ORIFICES

14 ANTERIOR & POSTERIOR VIEWS

15 HEART

16 17 THE HEART: THE GREAT VESSELS

Anterior view Posterior view 18 HEART

19 HEART

20 21 RIGHT ATRIUM • Developed from the right half of the sinus venarum and right half of the primitive atrium that emerged to form a single chamber • The heart rotation took other chambers away from their original orientation leaving the right atrium forming the right margin of the heart • Interiorly, a cubical atrium with cristal terminalis seen corresponding in position to a faint sulcus terminalis exteriorly, indicating where the 2 primitive chambers merge • Posteriorly to the crista terminalis is a smooth-walled area that developed from the embryonic sinus venosus and receives the SVC, IVC, coronary sinus, and anterior cardiac veins • Portion in front is tabeculated, it developed from primitive atrium

22 RIGHT ATRIUM contd

• Parallel ridges running forward from the cristal terminalis towards the auricle are the pectinate muscles • From the lower end of the crista terminalis is a prominent fold of endocardium, IVC valve, passes in front of IVC to become continuous with the crescentric margin of depression, the fossa ovale • It is an oval-shaped depression in the interatrial septum and represents the site of the foramen ovale, through which blood runs from the right atrium to the left atrium before birth. It forms the medial wall of the right atrium. • Orifice of the coronary sinus opens between the orifice of the IVC and orifice of the triscuspid orifice at the anterior wall. This is guarded by the fold, often perforated like a lace, the valve of the coronary sinus, detached from the valve of the IVC

23 24 LEFT ATRIUM

• Forms 2/3 of the back of the heart and its auricle peeps around the left border • Demacated from the left ventricle below by the coronary sinus • Right and left pulmonary veins open into it near its right and left margins • Auricle is trabeculated , the rest of the cubical cavity is smooth • The 4 pulmonary veins open at the posterior wall, the left AV or Mitral orifice replaces the anterior wall • Interatrial septum set obliquely because the left atrium was rotated to lie posterior to the right atrium

25 VENTRICLES

• Left & Right ventricles lie in front of their atria. • Form the apex of the heart -inferior surface -left margin diaphragmatic surface -most of the left margin -sternocostal surface -trivial part of the base(back)

26 VENTRICLES (contd) • Walls of the ventricles is proportional to amount of work each does • Rotation of the heart causes 1/3 of the left ventricle to face anteriorly & 2/3 of the left and 1/3 of the right ventricle to face inferiorly. • Internally, the right ventricle is triangle, the left is conical and narrow to the aorta • AV orifices are posterior • Exit or orifice of aorta and pulmonary trunk are superior • Ventricular walls lined with muscular bundle, trabeculae carneae which project into the cavity of the ventricle • Some of the bundles are merely elevated ridges, others attached at both ends like bridge- the septomarginal band ,

others form fingerlike projections- papillary muscles 27 VENTRICLES (cont)

• Anterior and posterior papillary muscles rises from the corresponding wall of each ventricle. Those on the left larger than those on the right. • In the right ventricle, small septal papillary muscle rise from the septum also. • From the apices of the papillary musles, fibrous cords, chordae tendineae pass to the cusp of the AV valves • Portion of the right ventricular cavity preceeding the pulmonary trunk is smooth and is called the conus arterious or infidibulum • On the left ventricle it is smooth, largely fibrous and nondistensible, it is called Aortic vestibule. It cannot contract nor dilate. • Interventricular septum is fleshy, except at its uppermost area that is membranous. • The fleshy part is an upgrowth of the apex; the membranous part is a downgrowth from the interatrial septum and right side of of the root of aorta. • Failure of the 2 to fuse result in an interventricular defect. 28 29 A-V VALVES

• Right is tricuspid and left is bicuspid • Chordae tendineae are attached to the edges and ventricular surfaces of the cusp, thus avoiding any obstruction to the incoming blood. • Chordae of each papillary muscle control the contiguous margin of 2 cusps: 2 papillary muscles on left & 3 on the right

30 31

32 SKELETON OF THE HEART

33 IMPULSE CONDUCTION SYSTEM

• Comprises sinoatrial node A-V node and A-V bundle and its 2 crura, right and left. • The sinoatrial node initiates the heart beat. Composed of peculiar, longitidudinally striated cells, it is 2cm long by 2mm wide and is situated along the upper end of the sulcus terminals. It is supplied by the right or left coronary artery (anastomoses are free) and by the right vagus nerve. • The atrioventricular node has the same structure and is situated in the interatrial spetum beside the mouth of the coronary sinus. It is also usually supplied by the right coronary artery (and anastomoses are free and ample) but by the left vagus nerve

34 35 36 • The atrioventricular bundle (of His) is a pale bundle of peculiar muscle fibers about 2 mm thick, enveloped in a loose sheath. This slender bundle is the sole muscular connection between the musculature of the atria and the musculature of the ventricles, it extends from the A-V node, through the fibrous skeleton, to the interventricular spetum. It skirts the hinder part of the membranous spetum and, at the upper part of the muscular spectrum, it divides into a right and a left crus. • The crura descend in their sheath, subndocardically, to the bases of the papillary muscles, that of the right side passing through the septomarginal (or moderator) band. When the anterior paplillary muscle arises near the septum, the band need not free itself from the septal wall in order to reach the papillary muscle. • Purkinje fibers, in connection with the fibers of the A-V bundle, ramify both subendocardically and throughout the myocardium of the ventricles.

37 BLOOD SUPPLY OF THE HEART

• Coronary arteries – Right coronary artery – Left coronary artery • Cardiac veins – Coronary sinus – Great cardiac vein – Middle cardiac vein small cardiac vein – Oblique vein of the Left atrium – Anterior cardiac vein – Smallest Cardiac Veins (Venae Cordis Minimae) • Collateral circulation – Cardiac – extracardiac

38 ARTERIAL & VENOUS SUPPLY

39 Nerve supply to the Heart

• Sympathetic • Cardiac plexus. • Distribution. • Branches of the cardiac plexus supply path in front of and behind the right pulmonary artery to the back of the atria, that supply, the right nerves controlling the sinoatrial (S-A) node. Other branches descend in front of the pulmonary trunk to join the right coronary plexus. They also pass forward, mainly on the sides of the pulmonary trunk, and as cardiac plexuses are distributed with the coronary arteries to the ventricles. • The vagal fibers are cardioinhibitory; the sympathetic fibers are cardioaccelerator, vasodilator, and sensory.

40 Text & Image Sources: Acknowledgement

• Drake, Vagi & Mitchell. 2015. Gray’s Anatomy for Students 3rd Ed; Churchill Livingstone Elsevier Inc. Philadelphia • Agur & Dalley II. 2013. Grant’s Atlas of Anatomy, 13th Ed; Lippincott Williams & Wilkins. Philadelphia. • Sinnatamby C.S. 2011. Last’s Anatomy Regional & Applied Anatomy, 12th Ed; Churchill Livingstone Elsevier Inc. Philadelphia • Moore, Dally II & Agur. 2014. Moore Clinically Oriented Anatomy. Lippincott Williams & Wilkins. Philadelphia. • Chung & Chung. 2012. BRS Gross Anatomy, 7th Ed; Lippincott Williams & Wilkins. Philadelphia. • Harold Ellis; 2006. Clinical Aantomy 11th Ed; Black Publishing • Basmajian J.V. Grant’s Method of Anatomy. 10th Ed. Williams & Wilkins

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