Ventricles of the Heart
The definition of heart ventricles can be summed up as the large, lower chambers of the fibromuscular organ that work to keep blood moving through the body. Although all parts of the heart work together to carry out its daily function, the ventricles have an enormous role in maintaining adequate cardiac output to keep blood flowing. The heart works continuously from the 4th gestational week until the end of life. Throughout this time, the muscular ventricles have the tremendous responsibility of pumping blood out of the heart and into the systemic and pulmonary circuits.
|Interventricular septum||Separates the left and right ventricles
Upper, thin membranous part
Lower, thick muscular part
Carries the atrioventricular bundles of His
|Ventricular function||Right - pumps blood to pulmonary circulation
Left - pumps blood to systemic circulation
|Embryology||Left ventricle arises from the primitive ventricle
Right ventricle arises from the bulbus cordis
|Ventricular pathology||Congenital ventricular disorders - ventricular septal defects, double outlet right ventricle, hypoplastic ventricles
Acquired - hypertrophy, pseudoaneurysm, arrhythmia, bundle-branch block
This article aims to discuss the development, anatomy, and function of the ventricles of the heart with an accompanying heart diagram to aid in understanding. Additional discussion regarding disorders of the ventricle (both congenital and acquired) will also be included.
Review of Cardiac Anatomy
The heart is a mediastinal structure that has the most important role in the circulatory system. In the anatomical position, the heart is obliquely positioned, with its anatomical base (formed by the left atrium) pointing posterolaterally to the right and the apex of heart directed anteroinferiorly to the left. The right cardiac chambers account for most of the anterior or sternocostal surface of the heart. However, the walls of both ventricles constitute the inferior or diaphragmatic surface.
Overviews about the heart and its surfaces are explained in the following videos:
The outer surface of the heart is marked by depressions known as grooves. They act as landmarks for the interatrial and interventricular septa inside the heart. The left and right pulmonary surfaces are made up by the left ventricle and right atrium, respectively. Of note, the left pulmonary surface rests in the cardiac notch of the left lung. The heart is made up of four muscular chambers that work synergistically to propel blood throughout the body. The heart is divided into two sides by the interatrial and interventricular septa. Each half of the heart has two chambers: an atrium, and a lower chamber called the ventricle. The function of the atria is to collect and pump blood into the ventricles. The function of the ventricles is to pump blood into systemic and pulmonary circulations. Details regarding the direction of the flow of blood can be found in the cardiac cycle article.
The atria are separated from the ventricles by the atrioventricular septa. This is a fibroelastic structure that not only prevents inappropriate blood flow from the atrium to the ventricle, but it also prevents unwanted electrical conduction from the atrial myocardium to the ventricles. In the absence of this structure, there would be backflow of blood and electrical activity across the myocardium.
However, blood is able to flow from each atrium into the ipsilateral ventricle via the respective atrioventricular valves, the tricuspid valve on the right and mitral valve on the left. Blood also leaves each ventricle via their respective ventricular outflow tracts that are guarded by the semilunar valves. On the left-hand side, this outflow tract is the aorta, which is guarded by the aortic valve. From here, blood flows into systemic circulation. On the right-hand side, the outflow tract is the pulmonary artery, which is guarded by the pulmonary valve. From here, blood flows into pulmonary circulation.
The right ventricle collects deoxygenated blood from the right atrium as the tricuspid valve relaxes and pumps it via rhythmic contractions through the pulmonary valve in its roof and into the pulmonary trunk which passes the blood onto the pulmonary artery and into the lungs.
It is bordered anterosuperiorly by the sternum and this circular convex area majorly contributes to the sternocostal surface of the heart. The inferior surface is situated upon the diaphragm and this small flat area makes up part of the diaphragmatic portion of the heart. The ventricular septum borders the right ventricle posteriorly and bulges somewhat into it, creating a transverse semilunar cross section.
The conus arteriosus, conical arterial pouch or infundibulum can be found in the upper left corner of the ventricle and gives rise to the pulmonary artery. The tendon of the conus arteriosus is a fibrous band that extends superiorly from the right atrioventricular fibrous ring and stretches between the posterior surface of the conus arteriosus and the aorta.
The right ventricular wall is three to six times thinner than the left because it starts off thicker and reduces in mass towards the apex. Despite this difference in muscle mass, the inner chambers of the ventricles are the same size and can accumulate approximately 85 millilitres in the adult.
The left ventricle receives blood from the left atrium of the heart via the relaxation of the mitral valve. When it contracts, it pushes the blood volume through the aortic valve and into the aorta. In comparison with the right ventricle, the left is both shorter in length and is transversely circular in a concave manner.
It forms the lesser part of the sternocostal surface of the heart anterosuperiorly, the larger part of the diaphragmatic surface inferiorly as well as the apex of the heart. The reason for the increased thickness of the left ventricular wall is that is has to be able to withstand the five times stronger contraction forces and blood pressure needed to propel the blood around the entire body without having it stall or collect anywhere.
It collects oxygenated blood returning from the lungs at approximately 80 mmHg and expels it into the aorta at around 120 mmHg during every heartbeat. The typical blood volume that can be pumped out of the heart per minute at rest, which is also known as the cardiac output, is about 5 liters/min and this numerical evaluation can increase to between 25 and even 45 liters/min in athletes during exercise.
Congenital Heart Defects
The ventricles can be deficient in several ways. Single ventricle defects fall into the category known as congenital heart defects, which are present at the time of birth. They are rare and affect only one side of the heart, either the left or the right ventricle at a time. The chamber may be smaller in comparison to its opposite cardiac quarter, underdeveloped or in some cases, the cardiac valve separating the ventricle from its atrium may be missing.
Several examples of well known ventricular defects have been mentioned below:
- Hypoplastic left heart syndrome occurs when one side of the heart is underdeveloped. In this case the left ventricle and the left atrium are too small a patent ductus arteriosus is present postpartum.
- Pulmonary atresia with an intact ventricular septum ensues when the pulmonary valve is completely aplastic. This means that the only blood that is being oxygenated by the lungs is that which shunts through the embryonic openings which remain patent.
- Finally, tricuspid atresia involves the aplasia of the tricuspid valve which sits between the right atrium and ventricle. blood cannot properly flow from the heart to the body and isn’t being oxygenated to an optimum level.