Heart valves are flap-like structures that allow blood to flow in one direction.

Systole phase: The ventricles contract and pump blood to the arteries.

Diastole phase: The heart ventricles are relaxed and the heart fills with blood.

Below are the two phases of the cardiac cycle: The Cardiac cycle is the sequence of events that occurs when the heart beats. Sinoatrial Node: A section of nodal tissue that sets the rate of contraction for the heart.Purkinje Fibers: Fiber branches that extend from the atrioventricular bundle.Atrioventricular Node: A section of nodal tissue that delays and relays cardiac impulses.Atrioventricular Bundle: A bundle of fibers that carry cardiac impulses.Heart nodes and nerve fibers play an important role in causing the heart to contract. Endocardium: The inner layer of the heart.Ĭardiac conduction is the rate at which the heart conducts electrical impulses.Myocardium: The muscular middle layer of the wall of the heart.Epicardium: The outer layer of the wall of the heart.Ventricles: Lower two chambers of the heart.Atria: Upper two chambers of the heart.Research on the CCS is an exciting and progressive area, and is likely to yield solutions to a number of problems in future. Animals whose morphology is similar to that of mature human CCS should be used for experimental and developmental research if the results are intended for human application. Recent advances in the understanding of CCS development have been introduced for cardiologists, anatomists, and biomedical researchers. Therefore, experimental data obtained in most mammals and birds are difficult to apply directly to humans. From the comparative anatomical viewpoint, there are marked differences between humans and most mammals and birds not only in the position of atrioventricular CCS in relation to surrounding structures but also in the morphology of the atrioventricular CCS. However, the atrioventricular CCS that is distal to the atrioventricular node (AVN) varies frequently in shape, size, and position with respect to some conventionally used landmarks.

In the elder human CCS, the sinuatrial node (SAN) is almost consistently positioned on the sulcus terminalis and is variable in size and shape with its extent. The main aim of this review is to provide macroscopic anatomical information on the human cardiac conduction system (CCS) with comparative morphological and developmental implications for future human application.

Gross anatomy of the human heart pdf