Internal structure of heart

The human heart is a four-chambered muscular organ that is roughly the size and form of a man’s closed fist, with two-thirds of its mass located to the left of the midline.

A pericardial sac surrounds the heart, which is lined with the parietal layers of a serous membrane. The epicardium is formed by the serous membrane’s visceral layer.

Internal structure of heart

Because of the pairs of chambers that pump blood into the circulation, the heart’s contraction cycle follows a twofold pattern of circulation—the pulmonary (lungs) and systemic (body) circuits. To gain a better knowledge of cardiac function, researchers must first investigate the interior anatomical components in greater depth.

A septum (plural = septa) is a wall or barrier that divides the heart into chambers and is derived from the Latin word septum, which means “that that encloses.”

The atrioventricular septum connects the atria and ventricles and is known as the heart’s valves. The presence of four apertures that allow blood to flow from the atria to the ventricles and from the ventricles to the pulmonary trunk and aorta distinguishes it. A valve, a specialised structure that assures one-way blood flow, is located in each of these openings between the atria and ventricles. The tricuspid (right side) and bicuspid (left side) valves are the valves that connect the atria and ventricles. The pulmonary and aortic valves are the valves at the apertures that lead to the pulmonary trunk and aorta, respectively.

The four chambers, major veins, and early branches, as well as the valves, are seen in this anterior view of the heart.

Right Atrium

The right atrium receives blood from the systemic circulation and returns it to the heart. The superior and inferior venae cavae are the two main systemic veins. The superior vena cava drains blood from the head, neck, upper limbs, and thoracic area above the diaphragm. It discharges into the right atrium’s superior and posterior sections.

 The inferior vena cava drains blood from the lower limbs and abdominopelvic region of the body, which are below the diaphragm. It, too, drains into the posterior atria, but below the superior vena cava’s entrance.

Right Ventricle

The tricuspid valve transports blood from the right atrium to the right ventricle. The chordae tendineae, or “tendinous cords,” are strong strands of connective tissue that attach each flap of the valve. They are poetically referred to as “heart strings.”

The pressure within the ventricular chamber rises when the ventricle’s myocardium contracts. Blood, like any other fluid, travels from places of higher pressure to areas of lower pressure, in this case toward the pulmonary trunk and atrium. 

The papillary muscles tighten as well, creating strain on the chordae tendineae to prevent backflow. During ventricular contraction, this prevents the flaps of the valves from being driven into the atria and blood regurgitation back into the atria. The papillary muscles and chordae tendineae linked to the tricuspid valve are shown in this diagram.

Left Atrium

Blood returns to the left atrium via one of the four pulmonary veins after gas exchange in the pulmonary capillaries. Blood flows almost continuously from the pulmonary veins back into the atrium, which serves as the reception chamber, and then into the left ventricle through an aperture. The Left AV or bicuspid valve guards the passage between the left atrium and ventricle. 

The thick-walled left ventricle’s myocardium pumps vigorously, generating enough pressure to push blood flow throughout the body. The blood travels through the aortic valve and enters the aorta when it leaves the left ventricle. Despite the fact that both sides of the heart pump the same amount of blood, the muscular layer is substantially thicker.The muscle layer in the left ventricle is substantially thicker than in the right, despite the fact that both sides of the heart pump the same quantity of blood.

Left Ventricle

The both sides of the heart pump the same volume of blood, the muscle layer in the left ventricle is significantly thicker than in the right. The left ventricle, like the right, bears trabeculae carneae, but no moderator band. The chordae tendineae connect the bicuspid valve to the papillary muscles. There are two papillary muscles in the human body. The left ventricle is the systemic circuit’s main pumping chamber, ejecting blood into the aorta via the aortic semilunar valve.

The left anterior descending artery, also known as the anterior interventricular artery (AIV), is a branch of the left coronary artery that continues to the heart. It’s found subepicardial in the heart’s anterior and inferior interventricular sulci.

Internal structure of the heart is marked by the anterior and posterior interventricular sulci

Conal, anterior ventricular, and interventricular septal branches emerge from the artery. They primarily feed blood to the anterior surface of the left ventricle and the anterior and inferior distal two-thirds of the interventricular septum. An obstruction of the AIV, which supplies huge portions of the heart with blood, can quickly result in a heart attack and death. As a result, it’s also known as the widow maker artery.

The AIV originates at the superior end of the anterior interventricular sulcus, from the left coronary artery. Within the anterior interventricular sulcus, it runs obliquely and anteroinferiorly over the anterior surface of the heart, towards the apex. Within the inferior interventricular sulcus, the AIV coils around the apex of the heart and continues superiorly along the inferior surface of the heart. The artery anastomoses with the right coronary artery’s anterior interventricular branch (also known as the posterior interventricular/posterior descending branch) about halfway down the inferior surface.

Branches and supply

The AIV is divided into various branches:

• The conal branch is a tiny branch that anastomoses with the bigger conus artery of the right coronary artery to supply the left side of the conus arteriosus.
• The right and left anterior ventricular branches are split. The right anterior ventricular branches are tiny, providing only a small portion of the right ventricle’s anterior surface, immediately close to the anterior interventricular sulcus. The branches of the left anterior ventricular chamber are more important. They run diagonally over the left ventricle’s anterior surface, supplying it with oxygenated blood. Up to seven or eight diagonal branches (D1-D7/D8) can emerge from the left anterior ventricular branch.
• There are two types of interventricular septal branches: anterior and inferior. The atrioventricular bundle and the anterior two-thirds of the interventricular septum are supplied by the anterior interventricular septal branches. The inferior interventricular septal branches supply the inferior interventricular septum’s distal part.

Using the articles, videos, quizzes, and graphics in the following study unit, master the branches of the coronary arteries, including the AIV.

Conclusion

Internal structure of heart Because of the pairs of chambers that pump blood into the circulation, the heart’s contraction cycle follows a twofold pattern of circulation in the pulmonary and systemic circuits. The atrioventricular septum connects the atria and ventricles and is known as the heart’s valves. The presence of four apertures that allow blood to flow from the atria to the ventricles and from the ventricles to the pulmonary trunk and aorta distinguishes it. The pulmonary and aortic valves are the valves at the apertures that lead to the pulmonary trunk and aorta, respectively. Right Atrium The right atrium receives blood from the systemic circulation and returns it to the heart. The muscle layer in the left ventricle is substantially thicker than in the right, despite the fact that both sides of the heart pump the same quantity of blood. The left anterior descending artery, also known as the anterior interventricular artery , is a branch of the left coronary artery that continues to the heart.