Describe the structure of the heart, including the chambers and valves. (pages \(94-96\) )

The heart is a muscular organ that pumps blood throughout the body. It consists of four main chambers: two atria and two ventricles. The atria receive blood, while the ventricles pump it out of the heart. In addition, there are four valves that ensure the proper flow of blood in one direction.

The heart is made up of the following four chambers: 1. Right Atrium: The right atrium collects deoxygenated blood returning from the body and sends it to the right ventricle. 2. Right Ventricle: The right ventricle pumps deoxygenated blood into the lungs for oxygenation through the pulmonary arteries. 3. Left Atrium: The left atrium collects oxygenated blood from the lungs and sends it to the left ventricle. 4. Left Ventricle: The left ventricle pumps oxygenated blood to the rest of the body through the aorta. These chambers contract and relax in a coordinated manner to efficiently move blood throughout the body.

There are four valves in the heart that ensure the proper flow of blood and prevent its backflow: 1. Tricuspid Valve: Located between the right atrium and right ventricle, it allows blood to flow from the right atrium to the right ventricle and prevents backflow. 2. Pulmonary Valve: Located between the right ventricle and the pulmonary artery, it allows blood to flow from the right ventricle to the lungs for oxygenation and prevents backflow to the right ventricle. 3. Mitral Valve: Also known as the bicuspid valve, it is located between the left atrium and left ventricle, allowing blood to flow from the left atrium to the left ventricle and preventing backflow. 4. Aortic Valve: Located between the left ventricle and the aorta, it allows blood to flow from the left ventricle to the rest of the body via the aorta. It also prevents backflow to the left ventricle.

The heart features a built-in electrical conduction system to coordinate the contractions of the four chambers and maintain a consistent heartbeat. The sinoatrial (SA) node, located in the right atrium, acts as the natural pacemaker, initiating the electrical impulses. These impulses travel to the atrioventricular (AV) node, which sends the signals along the Bundle of His, dividing into right and left bundle branches and finally ending in the Purkinje fibers. This complex system ensures the chambers of the heart contract and relax in a coordinated and efficient manner. Now we have provided a brief overview of the structure of the heart, including its chambers and valves, as well as the conduction system that coordinates its functioning.