Anatomy of the Heart

Anatomy of the Heart

• Orientation: The heart is obliquely oriented, with its apex pointing downwards and to the left, located in the 5th intercostal space. The base is superior and near the origins of great vessels, approximately at the 2nd intercostal space. The heart is positioned roughly two-thirds to the left of the midline.
• Anterior/Inferior Aspect: The anterior and inferior aspect of the heart is primarily composed of the right atrium and ventricle.
• Posterior/Superior Aspect: The posterior and superior aspect of the heart is primarily composed of the left atrium and ventricle.
• Mediastinum: The mediastinum is divided into superior and inferior sections by a horizontal imaginary plane through the sternal angle. The inferior mediastinum further divides into anterior, middle, and posterior parts. The heart and pericardium reside within the middle mediastinum.

Heart Coverings

• Fibrous Pericardium: The fibrous pericardium is the tough, outermost layer of the sac surrounding the heart. It is attached to the diaphragm inferiorly and fuses with the great vessels superiorly.
• Serous Pericardium: This double-layered membrane is part of the pericardium. A parietal layer lines the fibrous pericardium and a visceral layer fully encases the heart. Between these layers is the pericardial cavity, containing a small amount of fluid which reduces friction during heart movement (pericardial fluid).

Sulci of the Heart

• Coronary Sulcus (Atrioventricular Sulcus): This groove encircles the heart, separating the atria and ventricles.
• Interventricular Sulcus: This groove divides the ventricles. It has anterior and posterior components.

Great Vessels

• Aorta: Arises from the left ventricle. The aorta has an ascending portion, an arch, and a descending portion. Ascending aorta has right and left aortic sinuses. Arch of the aorta begins and ends at T4/T5 or sternal angle.
• Pulmonary Trunk: Originates anterior to the aorta from the right ventricle.
• Superior Vena Cava (SVC): Empties into the right atrium.
• Inferior Vena Cava (IVC): Empties into the right atrium.

Aorta

• Ascending Aorta: Possesses right and left aortic sinuses.
• Arch of Aorta: Begins and ends at the sternal angle (T4/T5). Main branches: brachiocephalic, left common carotid, and left subclavian arteries.
• Thoracic Aorta: Lies anterior to the trachea.

Ligamentum Arteriosum

• A remnant of the embryonic ductus arteriosus.
• Connects the aortic arch to the pulmonary trunk/left pulmonary artery.
• Landmark for identifying the left recurrent laryngeal nerve.

Heart Chambers and Valves

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.
• Valves:
  • Leaflet Valves: Tricuspid (RA-RV), Bicuspid (Mitral valve, LA-LV)
  • Cusped (Semilunar) Valves: Aortic (LV-aorta), Pulmonic (RV-pulmonary trunk)

Right Atrium

• Auricle: (ear-like appendages)
• Pectinate Muscles: Rough ridges of myocardium in the auricle regions.
• Sinus Venarum: Smooth area between the superior/inferior vena cava and coronary sinus.
• Crista Terminalis: Divides the rough and smooth regions.
• Openings (ostia): For the SVC, IVC and Coronary Sinus
• Fossa Ovalis: Remnant of the foramen ovale in the fetus
• Limbus: Border of the fossa ovalis

Right Atrium "Valves"

• Superior Vena Cava: No valve
• Inferior Vena Cava: Eustachian valve (incompetent in adults, directs blood from IVC through the foramen ovale in the fetus).
• Coronary Sinus: Thebesian valve (Prevents backflow during atrial systole)

Left Atrium

• Ostia of 4 Pulmonary Veins (2 superior, 2 inferior): Openings for venous return that connect with the left atrium
• Auricle (ear-like appendage)

Right Ventricle

• Most anterior aspect: Of the heart
• Tricuspid Valve (RA-RV): Composed of anterior, posterior, and septal cusps.
• Papillary Muscles: Connected to the valve cusps by chordae tendineae.
• Chordae Tendineae: Prevent valve regurgitation upon ventricular contraction.
• Trabeculae Carnae: Irregular muscular ridges with in the chamber.
• Moderator Band: Transmit signal for contraction of the papillary muscle.

Left Ventricle

• Trabeculae Carnae: Irregular muscular ridges within the chamber.
• Bicuspid (Mitral) Valve (LA-LV): Composed of anterior and posterior cusps.
• Papillary Muscles: Much larger than in the right ventricle.
• Chordae Tendinae: Prevent valve regurgitation upon ventricular contraction.
• Usually a greater number of papillary muscles and chordae tendineae than in the right ventricle, due to the higher pressure required.

Pulmonic Valve

• Function: Valves control blood flow from the right ventricle to the pulmonary trunk.
• Location: Lies just anterior to the aortic valve.
• Cusps: 3 semilunar cusps (Anterior, Right, Left).

Aortic Valve

• Function: Valves control blood flow from the left ventricle to the aorta.
• Location: Posterior to the pulmonic valve.
• Cusps: 3 semilunar cusps (Posterior, Right, and Left). Openings for the coronary arteries located superior to the cusps.

Heart Valves

• Tricuspid valve: RA-RV (Three cusps)
• Bicuspid (Mitral) valve: LA-LV (Two cusps)
• Aortic valve: LV-Aorta (Three cusps)
• Pulmonic valve: RV-Pulmonary Trunk (Three cusps)

Conducting System

• Components necessary for the heart's rhythmic beat.
• Consists of the sinoatrial (SA) node, internodal pathways, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.

Right Coronary Blood Supply

• Right Coronary Artery: Originates from the right aortic sinus. Travels in the right coronary groove (AV sulcus). Branches include: Right Marginal Arteries, branches to the SA and AV nodes, and Posterior Interventricular Artery.

Left Coronary Blood Supply

• Left Coronary Artery: Originates from the left aortic sinus. Superior to the left aortic cusp, and has branches: the Left Anterior Descending (LAD) artery and its sepatl and diagonal branches, Left circumflex artery (and left marginal branches)

Dominance

• Dominance: Determined by which artery (right or left) gives rise to the posterior interventricular artery.
  • Predominantly right coronary dominance (80%)
  • Left coronary or codominance are less common (<20%).

Venous Drainage of the Heart

• Coronary Sinus: Main venous drainage at the posterior portion of the coronary groove collecting blood from other major coronary veins (i.e. great cardiac, middle cardiac and small cardiac veins) into the right atrium.
• Great Cardiac Vein: Drains blood from the anterior interventricular portion.
• Middle Cardiac Vein: Drianage from the posterior interventricular sulcus.
• Small Cardiac Vein: Drains blood from the right coronary sulcus,
• Oblique Vein (of the Left Atrium): Drains blood from the left atrium,
• Posterior Vein of the Left Ventricle: Drains the posterior left ventricle.