Heart Anatomy and Pericardium Quiz

Pericardium

• Visceral pericardium forms the epicardium, the external layer of the heart wall
• Visceral pericardium becomes continuous with the parietal pericardium, which is fused to the fibrous pericardium
• The pericardial cavity is a potential space between the parietal and visceral layers, containing a thin film of serous fluid (10-20 ml)
• Pericardial effusion is a fluid collection in the pericardial cavity
• Fibrinous inflammation can lead to adhesions that restrict heart motion
• Aortic rupture can cause rapid blood accumulation in the pericardial cavity, leading to pericardial tamponade

Heart Surface Anatomy

• Superior Border: Horizontal line between the junction of the third costal cartilage and sternum
• Right Border: Between the third and fifth right costal cartilages, approximately 3 cm from the midline (or 1-2 cm from the right sternal margin)
• Inferior Border: From the fifth right costal cartilage to the apex, which lies behind the fifth left intercostal space (8-9 cm from midline or 1 cm right from the left midclavicular line)
• Left Border: Slopes upward and medially from the heart apex to the left third costal cartilage junction with the bony part (approximately 3 cm from midline or 1.2 cm from the left sternal margin)

Heart Structure

• The heart has a base, apex, sternocostal (anterior), diaphragmatic surfaces, right, left, and inferior margins
• Composed of four chambers: two atria and two ventricles
• External sulci include the coronary sulcus and anterior and posterior interventricular sulci

Heart Base

• Located between the coronary sulcus and the bifurcation of the pulmonary trunk
• Formed by the right and left atria and proximal parts of the great vessels
• Great vessels on the base include:
  • Superior vena cava
  • Inferior vena cava
  • Pulmonary veins (4)
  • Aorta
  • Pulmonary trunk

Heart Composition

• Stroma: Fibrous skeleton
• Parenchyma: Myocardial fibers

Heart Wall Layers

• Epicardium: External, serous pericardium
• Myocardium: Middle, muscular layer
• Endocardium: Internal, endothelial lining of the heart

Fibrous Skeleton

• Fibrous connective tissue network of collagen and elastic fibers
• Contains fibrous rings encircling the orifices of the aorta, pulmonary trunk, and atrioventricular orifices
• Functions:
  • Keeps orifices patent and prevents over-distention
  • Provides attachment for valves
  • Provides attachment for myocardium layers
  • Separates electrical impulses of atria and ventricles

Myocardium - Cardiomyocytes

• Distinguishing feature: Intercalated discs, which anchor cardiac muscle cells together and allow free passage of ions
• Forms a functional syncytium
• Two types of cardiomyocytes:
  • Contracting myocardium (99%)
  • Specialized cardiomyocytes of the conduction system

Atrial Myocardium

• 2-4 mm thick
• Superficial layer extends over both atria
• Deep layer is particular for each atrium
• Circular and transverse fibers form the inter-atrial septum and attach to atrioventricular fibrous rings
• Pectinate muscles are parallel ridges in the auricle, resembling teeth of a comb
• Produces atrial natriuretic hormone, which lowers blood pressure by increasing water and sodium excretion in the kidneys and regulating vascular tone

Ventricular Myocardium

• Right ventricle is thinner walled than left ventricle (5-8 mm vs. 10-15 mm)
• Right ventricle: low pressure pump
• Left ventricle: high pressure pump
• Three layers of myocardium:
  • Outer layer: Common to both ventricles, originates from anterior part of AV rings
  • Middle layer: Fibers are parallel to AV rings
  • Inner layer: Helical orientation, only in left ventricle
• Trabeculae carneae are irregular muscular elevations on the inner surface of ventricles, except in the conus arteriosus
• Papillary muscles are conical structures to which chordae tendineae attach

Semilunar Valves

• Opened when ventricular pressure is higher than arterial pressure, allowing blood flow
• Close during ventricular relaxation

Pulmonary Valve

• Consists of right, left, and anterior valvules

Aortic Valve

• Larger, thicker, and stronger than the pulmonary valve
• Consists of right, left, and posterior valvules
• Aortic sinuses (Valsalva) are dilated pockets between the valvules and aortic wall, promoting non-turbulent flow into coronary arteries
• Valve closes during ventricular diastole, allowing blood flow into coronary arteries
• Aortic insufficiency leads to regurgitation of blood during ventricular diastole
• Aortic stenosis leads to narrowing of the valve and reduced opening

Right Atrium

• Receives oxygen-poor blood from the body via the inferior vena cava, superior vena cava, and coronary sinus
• Contains the right auricle and pectinate muscles
• Crista terminalis is a muscular ridge between the openings of the caval veins
• Sinus of venae cavae is a part of the atrium posterior to the crista terminalis
• Interatrial septum contains the oval fossa, a remnant structure of the embryonic oval foramen
• Contains the orifice of the coronary sinus above the septal cusp
• Contains the sinoatrial and atrioventricular nodes
• Has the right atrioventricular orifice

Right Ventricle

• Receives oxygen-poor blood from the right atrium through the atrioventricular orifice
• Pumps blood to the pulmonary circulation via the pulmonary orifice and trunk
• Conus arteriosus lacks trabeculae carneae

Cardiac Conduction System

• Atrial musculature rapidly transmits signals to the atrioventricular node (AV node)
• AV node is located in the interatrial septum between the opening of the coronary sinus and the septal cusp of the tricuspid valve
• AV node has slow conduction, briefly delaying signals (0.09-0.1 seconds)
• Ventricles are electrically isolated from atria, preventing simultaneous contraction
• Atrioventricular bundle (bundle of His) penetrates the right fibrous triangle and reaches the superior part of the muscular interventricular septum
• Bundle of His divides into right and left bundles (crus)
• Peripheral fibers of the bundles are Purkinje fibers, which conduct rapidly (4 m/s) and initiate contraction

Coronary Circulation

• The heart has its own blood supply system
• Blood in the chambers doesn't nourish the myocardium
• Supplied by the right and left coronary arteries
• Almost all venous blood from the heart drains into the right atrium via the coronary sinus
• Names of veins don't correspond to those of arteries
• Anastomoses between arteries are not sufficient to maintain perfusion if one side of the coronary circulation is occluded
• Coronary circulation can develop collateral systems in situations of ischemic heart disease

Left Coronary Artery

• Arises from the left aortic sinus
• Lies between the pulmonary trunk and left auricle
• Divides into branches:
  • Circumflex artery: Curves left in the coronary sulcus but does not descend in the posterior interventricular sulcus
  • Anterior interventricular artery (left anterior descending, LAD): Desends in the anterior interventricular sulcus, supplies apex and anterior ventricular walls
• Both arteries anastomose at the posterior aspect of the heart

Test your knowledge on the anatomy of the heart and its surrounding structures, particularly the pericardium. This quiz covers vital concepts such as the layers of the pericardium, the pericardial cavity, and heart surface anatomy. Ideal for students studying cardiology or human anatomy.