Development of the heart, respiratory, and circulatory systems

Abstract

The development of the circulatory and respiratory systems no longer occupies the time they once used to in dental curricula in the United Kingdom (UK). Apart from the intrinsic curiosity of knowing how two of the major body systems develop, the main reason that they were on the dental curricula was the same as any other aspect of developmental anatomy—the consequences of developmental abnormalities on the planning and execution of dental care. The diagnosis and treatment of developmental heart abnormalities has advanced so rapidly in recent years that people born with such conditions can now be treated so successfully that they can often live symptom-free for the rest of a normal lifespan. The adverse effects of heart defects on the functions of the circulatory and respiratory systems are less likely to be encountered and taken into account during dental treatment; people with problems that do impact on their general health are now most likely to be seen in specialist units. The same does not pertain in developing countries. This brief account is presented to provide an overview of the development of the two systems where knowledge of developmental defects and their consequences on the physiology of the circulatory and respiratory systems is required. The circulatory system must develop to a functional state before any other system in the body. The embryo does not need to grow very much before it reaches such a size that diffusion of nutrients from the surrounding fluids is no longer adequate to fulfil its nutritional requirements. The cardiovascular system must, therefore, be established and begin to function very early on in development. Even while the embryo is in the trilaminar stage, a primitive circulatory system is established that connects the embryo to the maternal circulation through the connecting stalk. The heart begins to develop soon after this as a single tube but an atrium and a ventricle can soon be distinguished. These chambers and the veins and arteries entering and leaving the heart are subsequently divided into two so that the right heart and pulmonary circulation and the left heart and systemic circulation are thus established.