Summary of The Cardiovascular System: An Overview

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The cardiovascular system is responsible for circulating blood throughout the body and is composed of the heart, blood vessels, and valves. The heart is a muscular pump that contracts and relaxes to push blood through the vessels and valves. The vessels are subdivided into arteries, veins, capillaries, and lymphatics. Pathologic conditions of the cardiovascular system can usually be mapped to one of its components.

• 00:00:00 The cardiovascular system is responsible for pumping blood around the body and is composed of four chambers, four valves, a handful of great vessels, and a number of minor vessels. Blood enters the heart through the right atrium, passes through a series of valves into the right and left ventricles, and exits the heart. The movement of oxygen is just one function of the cardiovascular system; blood also transports metabolic waste products, hormones, and essential components of the immune system.
• 00:05:00 The cardiovascular system consists of the heart, valves, and vessels. The heart consists of two left and two right ventricles, an atrial septum, and valves. The valves include leaflets and cusps, and each valve belongs to one side of the heart. The conduction system sends electrical signals between the atria and ventricles. Eight great vessels bring blood from the body to the heart.
• 00:10:00 The cardiovascular system is a mechanical pump that depends on the conduction system to deliver electrical signals to different chambers at different times. The system normally operates at a balance between the sympathetic and parasympathetic divisions of the autonomic nervous system, resulting in a resting heart rate between 50 and 90 beats per minute. The conduction system delivers electrical signals to the atria and av nodes, which in turn trigger their contraction and the ejection of blood through the valves into the ventricles. After holding up the signal by a hundred or so milliseconds, the a b node allows the impulse to continue through a band of conducting fibers called the hiss bundle, which divides into right and left bundle branches which travel to the right and left ventricles, respectively. The right and left bundles terminate in a network called the purkinje fibers, which rapidly deliver the signal to the ventricles. The overall consequence of this system is the rapid and nearly simultaneous contraction of the right and left ventricles in a wavefront that begins inferiorly at the cardiac apex and travels upwards towards the valves. This helps to increase the efficiency with which the heart ejects blood. In three dimensions, the heart is difficult to accurately represent anatomically,
• 00:15:00 The cardiovascular system includes the heart, blood vessels, and valves. The heart beats in a cycle, triggered by the sa node firing an electrical signal. Atrial contraction squeezes blood through the open valves into the right and left ventricles, and this period of atrial contraction is formally referred to as atrial systole. After the electrical signal undergoes the av delay, ventricular contraction occurs. The pressure gradient within the ventricles causes the av valves to quickly snap shut, triggering the first heart sound - known as s1. Ventricular diastole follows, during which the ventricles relax and the pressure in the atria is now higher than in the ventricles. The av valves open once again and blood is passively filled into the ventricles. The timing of ventricular diastole includes atrial systole, which is why atrial systole is usually referred to as the atrial kick or sometimes just atrial contraction.
• 00:20:00 The cardiovascular system consists of the heart and blood vessels. The heart is composed of three layers: the inner endocardium, the sub endocardium, and the myocardium. The myocardium is composed of cardiomyocytes and is responsible for the contraction of the heart muscle. The blood vessels are the conduits through which blood circulates throughout the body. The lymphatics are responsible for returning extravascular fluid to the bloodstream. The histology of the heart reveals that it is composed of three layers: the inner endocardium, the sub endocardium, and the myocardium. The pericardium is a fibrous structure that surrounds the heart.
• 00:25:00 The cardiovascular system consists of a tough outer fibrous pericardium, a inner smooth serous pericardium, and a pericardial space between the two. Pathologic conditions of the system can usually be mapped to one of these components, such as heart failure, myocarditis, or pericardial effusions. The blood vessels can be subdivided into arteries, veins, capillaries, and lymphatics.