The Pericardium and Heart Anatomy PDF

**The pericardium** The pericardium comprises fibrous and serous components. **[The fibrous pericardium]** a strong layer which covers the heart. Continuous superiorly with the tunica adventitia (perivascular connective tissue) of the great vessels entering and leaving the heart and with the p...

**The pericardium** The pericardium comprises fibrous and serous components. **[The fibrous pericardium]** a strong layer which covers the heart. Continuous superiorly with the tunica adventitia (perivascular connective tissue) of the great vessels entering and leaving the heart and with the pretracheal layer of deep cervical fascia. Attached anteriorly to the posterior surface of the sternum by the sternopericardial ligaments Bound posteriorly by loose connective tissue to structures in the posterior mediastinum. Continuous inferiorly with the central tendon of the diaphragm protects the heart against sudden overfilling **[The serous pericardium]** lines the fibrous pericardium (parietal layer) and is reflected at the vessel roots to cover the heart surface (visceral layer). The serous pericardium provides smooth surfaces for the heart to move against **[Pericardial cavity ]** the potential space between opposing layers of the parietal and visceral layers of serous pericardium. It normally contains a thin film of fluid that enables the heart to move and beat in a frictionless environment **[Two important sinuses are located between the parietal and visceral layers]**: **Transverse sinus** bounded posteriorly by the superior vena cava and left atrium and anteriorly by the pulmonary trunk and aorta **Oblique sinus** The sinus is a blind sac (cul-de-sac) A wide pocket-like recess in the pericardial cavity posterior to the base (posterior aspect) of the heart, formed by the left atrium Bounded laterally by the pericardial reflections surrounding the pulmonary veins and IVC and posteriorly by the pericardium overlying the anterior aspect of the esophagus **[The arterial supply of the pericardium ]** mainly the **pericardiacophrenic artery, a branch of the internal thoracic artery**, that often *[accompanies the phrenic nerve to the diaphragm.]* **Smaller contributions of blood come from the:** [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.] **[the venous drainage ]** **Pericardiacophrenic veins, tributaries of the brachiocephalic** (or internal thoracic) veins. Variable **tributaries of the azygos venous system** **[The nerve supply ]** **Phrenic nerves (**C3--C5), primary source of sensory fibers; pain sensations conveyed by these nerves are commonly referred to the skin (C3--C5 dermatomes) of the ipsilateral supraclavicular region (top of the shoulder of the same side). **Vagus nerves**, function uncertain. **Sympathetic trunks**, vasomotor. **Heart** Slightly larger than one's loosely clenched fist The heart appears trapezoidal from an anterior or posterior view **[APEX (directed anteriorly and to the left]**) Is formed by the inferolateral part of the left ventricle. Lies posterior to the left 5th intercostal space in adults Remains motionless throughout the cardiac cycle. Is where the sounds of mitral valve closure are maximal (apex beat **[BASE ]** Is the heart's posterior aspect (opposite the apex). Is formed mainly by the left atrium, with a lesser contribution by the right atrium. Faces posteriorly toward the bodies of vertebrae T6--T9 and is separated from them by the pericardium, oblique pericardial sinus, esophagus, and aorta. Extends superiorly to the bifurcation of the pulmonary trunk and inferiorly to the coronary sulcus. Receives the pulmonary veins on the right and left sides of its left atrial portion, and the superior and inferior venae cavae at the superior and inferior ends of its right atrial portion. **[The four borders of the heart are the]**: 1\. **Right border (slightly convex)**, formed by the right atrium and extending between the SVC and the IVC. 2**. Inferior border (nearly horizontal)**, formed mainly by the right ventricle and slightly by the left ventricle. 3\. **Left border (oblique, nearly vertical)**, formed mainly by the left ventricle and slightly by the left auricle. 4\. **Superior border**, formed by the right and left atria and auricles **[The heart surfaces]** **The anterior (sternocostal) surface** comprises the: *[right atrium, atrioventricular groove, right ventricle, a small strip of left ventricle and the auricle of the left atrium]*.  **The inferior (diaphragmatic) surface** comprises the: *[right atrium, atrioventricular groove and both ventricles separated by the interventricular groove. ]*  **The posterior surface (base**) comprises the *[left atrium receiving the four pulmonary veins.]* **[The wall of each heart chamber consists of three layers, from superficial to deep ]** 1\. Endocardium, a thin internal layer (endothelium and subendothelial connective tissue) or lining membrane of the heart that also covers its valves. 2\. Myocardium, a thick, helical middle layer composed of cardiac muscle. 3\. Epicardium, a thin external layer (mesothelium) formed by the visceral layer of serous pericardium **[The heart has four chambers]**: 1. Right and left atria; are the receiving chambers that pump blood into the ventricles (the discharging chambers). 2. Right and left ventricles. **[Coronary sulcus (atrioventricular groove]**) Demarcates atria from the ventricles **[Anterior and posterior interventricular (iv) sulci (grooves]**) Demarcates right and left ventricles from each other **[cardiac cycle]** The synchronous pumping actions of the heart's two atrioventricular (AV) pumps (right and left chambers) constitute the cardiac cycle The cycle begins with a period of ventricular elongation and filling (diastole) and ends with a period of ventricular shortening and emptying (systole) **[Heart sounds]** A lub (1st) sound as the blood is transferred from the atria into the ventricles, heard with a stethoscope. A dub (2nd) sound as the ventricles expel blood from the heart, heard with a stethoscope. The heart sounds are produced by the snapping shut of the one way valves **[The fibrous skeleton of the heart ]** **Four fibrous rings** (l. Anuli fibrosi) a complex framework of dense collagen that surround the orifices of the valves **A right and left fibrous trigone** (formed by connections between rings) **The membranous parts of the interatrial and interventricular septa.**  **The fibrous skeleton of the heart:** Keeps the orifices of the AV and semilunar valves patent and prevents them from being overly distended by an increased volume of blood pumping through them. Provides attachments for the leaflets and cusps of the valves. The cardiac muscle fibers are anchored to the fibrous skeleton of the heart Forms an electrical "insulator," by separating the myenterically conducted impulses of the atria and ventricles so that they contract independently and by surrounding and providing passage for the initial part of the AV bundle of the conducting system of the heart **[RIGHT ATRIUM]** **The right atrium forms the right border of the heart** **Receives deoxygenated blood from** ; the **inferior vena cava below**(The IVC opens into the inferior part of the right atrium almost in line with the SVC at approximately the level of the 5th costal cartilage) and From the **superior vena cava above**.( the svc opens into the superior part of the right atrium at the level of the right 3rd costal cartilage) **Receives the coronary sinus in its lower** part (The opening of the coronary sinus, a short venous trunk receiving most of the cardiac veins, is between the right AV orifice and the IVC orifice) The ear-like **right auricle** is a conical muscular pouch that projects from this chamber like an add-on room, increasing the capacity of the atrium as it overlaps the ascending aorta. **The interior of the right atrium has a**: Smooth, thin-walled, posterior part (**the sinus venarum**) on which the venae cavae (SVC and IVC) and coronary sinus open, bringing poorly oxygenated blood into the heart. Rough, muscular anterior wall composed of pectinate muscles (L. musculi pectinati). Right AV orifice through which the right atrium discharges the poorly oxygenated blood it has received into the right ventricle. **sulcus terminalis or terminal groove** The smooth and rough parts of the atrial wall are separated externally by a shallow vertical groove, the sulcus terminalis or terminal groove **crista terminalis or terminal crest** The smooth and rough parts of the atrial wall are separated internally by a vertical ridge, the crista terminalis or terminal crest **the oval fossa (L. fossa ovalis)** an oval, thumbprint-size depression on the interatrial septum separating the atria. which is a remnant of the oval foramen (L. foramen ovale) and its valve in the fetus Its floor is the **fetal septum primum**. The *[upper ridge of the fossa ovalis is termed]* the **limbus**, which **represents the septum secundum**. *[Failure of fusion of the septum primum with the septum secundum gives rise to a patent foramen ovale (atrial septal defect)]* **[THE RIGHT VENTRICLE]** Forms the largest part of the anterior surface of the heart, a small part of the diaphragmatic surface, and almost the entire inferior border of the heart Receives blood from the right atrium through the tricuspid valve Superiorly it tapers into an arterial cone, the **conus arteriosus (infundibulum)**, which leads into the pulmonary trunk. The **infundibulum is the smooth walled outflow tract** of the right ventricle. The **pulmonary valve is situated at the top of the infundibulum**. It is composed of three semilunar cusps. the pulmonary valve at the apex of the conus arteriosus is at the level of the left 3rd costal cartilage. The **edges of the valve cusps are attached to chordae tendineae which are, in turn, attached to papillary muscles**(projections of muscle bundles on the ventricular wall) A thick muscular ridge, **the supraventricular crest, separates the ridged muscular wall of the inflow part of the chamber from the smooth wall of the conus arteriosus**, or outflow part The wall of the right ventricle is thicker than that of the atria but not as thick as that of the left ventricle. The **interior of the right ventricle has irregular muscular elevations (trabeculae carneae**) **interventricular septum** composed of muscular and membranous parts, a partition between the right and left ventricles **moderator band (or septomarginal trabecula**) a prominent bundle that projects forwards from the interventricular septum to the anterior wall. it is of importance in the conduction of impulses as it **contains the right branch of the atrioventricular bundl**e.  **[LEFT ATRIUM ]** T**he left atrium forms most of the base of the hea**rt A **slightly thicker wall than that of the right atrium** **Receives oxygenated blood from four pulmonary veins (two** superior and two inferior) which drain posteriorly into its smooth posterior wall **The cavity is smooth walled except for the atrial appendage** The tubular, muscular left auricle, its wall trabeculated with pectinate muscles, forms the superior part of the left border of the heart and overlaps the root of the pulmonary trunk. It represents the remains of the left part of the primordial atrium. **A semilunar depression in the interatrial septum indicates the floor of the oval fossa**; the surrounding ridge is the valve of the oval fossa (L. valvulae foramen ovale). **The mitral (bicuspid) valve guards the passage of blood from the left atrium to the left ventricle.** **[LEFT VENTRICLE]** **The left ventricle forms the apex of the heart**, nearly all its left (pulmonary) surface and border, and most of the diaphragmatic surface **The wall of the left ventricle is considerably two to three times thicker than that of the right ventricle** but the structure is similar. **The thick wall is necessary to pump oxygenated blood at high pressure through the systemic circulation**. Because arterial pressure is much higher in the systemic than in the pulmonary circulation, the left ventricle performs more work than the right ventricle **Walls that are mostly covered with a mesh of trabeculae carneae t**hat are finer and more numerous than those of the right ventricle. **Trabeculae carneae project from the wall with papillary muscles attached to the mitral valve cusp edges by way of chordae tendineae**. Anterior and posterior papillary muscles that are larger than those in the right ventricle A conical cavity that is longer than that of the right ventricle. **The aortic vestibule is a smooth walled part of the left ventricle which is located below the aortic valve and constitutes the outflow tract** An aortic orifice that lies in its right posterosuperior part and is surrounded by a fibrous ring to which the right posterior, and left cusps of the aortic valve are attached; **the ascending aorta begins at the aortic orifice** **A double-leaflet mitral valve that guards the left AV orifice**  **[The heart valves]** The purpose of valves within the heart is to maintain unidirectional flow. **The tricuspid valve** Guards the right AV orifice. The bases of the valve cusps are attached to the fibrous ring around the orifice. the fibrous ring maintains the caliber of the orifice Tendinous cords (L. chordae tendineae) attach to the free edges and ventricular surfaces of the anterior, posterior, and septal cusps, much like the cords attaching to a parachute The tendinous cords arise from the apices of papillary muscles, which are conical muscular projections with bases attached to the ventricular wall. The papillary muscles begin to contract before contraction of the right ventricle, tightening the tendinous cords and drawing the cusps together. regurgitation of blood (backward flow of blood) from the right ventricle back into the right atrium is blocked during ventricular systole by the valve cusps Three papillary muscles in the right ventricle correspond to the cusps of the tricuspid valve 1\. **The anterior papillary muscle, the largest and most prominent of the three,** arises from the anterior wall of the right ventricle; its **tendinous cords attach to the anterior and posterior cusps of the tricuspid valve.** 2\. The **posterior papillary muscle**, smaller than the anterior muscle, may consist of several parts; it **arises from the inferior wall of the right ventricle**, and its **tendinous cords attach to the posterior and septal cusps of the tricuspid valve.** 3\. **The septal papillary muscle arises from the interventricular septum**, and **its tendinous cords attach to the anterior and septal cusps of the tricuspid valve** **the mitral valve** Has two cusps, anterior and posterior. The mitral valve is located posterior to the sternum at the level of the 4th costal cartilage. Each of its cusps receives tendinous cords from more than one papillary muscle. These muscles and their cords support the mitral valve, allowing the cusps to resist the pressure developed during contractions (pumping) of the left ventricle **SEMILUNAR VALVES** Semilunar cusps of the pulmonary valve (anterior, right, and left) are concave when viewed superiorly Semilunar cusps of the aortic valve (posterior, right, and left) are concave when viewed superiorly Semilunar cusps do not have tendinous cords to support them. They are smaller in area than the cusps of the AV valves, and the force exerted on them is less than half that exerted on the cusps of the tricuspid and mitral valves. The cusps project into the artery but are pressed toward (and not against) its walls as blood leaves the ventricle. After relaxation of the ventricle (diastole), the elastic recoil of the wall of the pulmonary trunk or aorta forces the blood back toward the heart. However, the cusps snap closed like an umbrella caught in the wind as they catch the reversed blood flow. They come together to completely close the orifice, supporting each other as their edges abut (meet), and preventing any significant amount of blood from returning to the ventricle The edge of each cusp is thickened in the region of contact, forming the lunule; the apex of the angulated free edge is thickened further as the nodule. **The aortic sinuses and sinuses of the pulmonary trunk (pulmonary sinuses) are the spaces at the origin of the pulmonary trunk and ascending aorta between the dilated wall of the vessel and each cusp of the semilunar valves** **The mouth of the right coronary artery is in the right aortic sinus, the mouth of the left coronary artery is in the left aortic sinus, and no artery arises from the posterior aortic (non-coronary) sinus**