the heart’s contraction cycle follows a dual pattern of circulation—the pulmonary (lungs)and systemic (body) circuits—because of the pairs of chambers that pump blood into the circulation. In order to develop a more precise understanding of cardiac function, it is first necessary to explore the internal anatomical structures in more detail.
The word septum is derived from the Latin for “something that encloses;” in this case, a septum (plural = septa) refers to a wall or partition that divides the heart into chambers.
Valves of the Heart: the septum between the atria and ventricles is known as the atrioventricular septum. It is marked by the presence of four openings that allow blood to move from the atria into the ventricles and from the ventricles into the pulmonary trunk and aorta. Located in each of these openings between the atria and ventricles is a valve, a specialized structure that ensures one-way flow of blood. The valves between the atria and ventricles are known generically as the tricuspid (right side)and the bicuspid (left side) valve. The valves at the openings that lead to the pulmonary trunk and aorta are known generically as the pulmonary and the aortic valve.
The longest day of the year isn't the hottest day of the year because the phenomenon of the hottest weather following the summer solstice by a month or two is called the lag of seasons.
