Over the course of class this week, we covered four different systems. Of those, I found great interest in the cardiovascular system. This system consists of the heart and blood vessels and is responsible for delivering oxygen and nutrients to all the organ systems in our bodies. It also circulates waste products to the appropriate organ systems so that they can be removed.
Contrary to popular belief of how the heart looks, it is actually a cone-shaped organ about the size of a fist. The hearts wall is composed of three different layers: the epicardium which is the outermost layer, the myocardium which is the middle layer, and the endocardium which is the innermost layer. It also has four chambers and four valves. The upper chambers are called the right and left atria and the lower chambers are the right and left ventricles. The four valves it contains are the tricuspid valve, bicuspid valve, pulmonary semilunar valve, and the aortic semilunar valve. All these make up the basic parts which work together to make one "lubb-dubb" also know as one heartbeat, or cardiac cycle.
The heart also has its own natural pacemaker called a sinoatrial node (SA node) which creates rhythmic contractions. It sends the impulse to the atrioventricular node (AV node) causing the atria to contract and send the impulse to the bundle of His followed by the purkinje fibers. This cycle is known as the cardiac conduction system. Physicians use tests called electrocardiograms (EKG) to determine if this system is functioning properly.
There are two routes the blood takes. The first one is from the heart to the lungs and back to the heart. This is called pulmonary circulation and its purpose is to oxygenate the blood. The second route is from the heart through the body and back to the heart. Its purpose is to deliver oxygen and nutrients to the body cells and to pick up carbon dioxide and waste products. This circuit is known as the systemic circuit.
Fun fact: It only takes blood about 20 seconds to make and entire trip around your body!
The blood circulation takes place in blood vessels and include arteries, arteriols, veins, venules, and capillaries. These parts help to determine our blood pressure. When the ventricles contract the pressure is at its highest in the arteries, this is called your systolic pressure, and at its lowest when the ventricles relax called diastolic pressure. If blood pressure becomes to low, vasoconstriction happens. This is when the blood vessel walls tighten to help raise it back up. If blood pressure becomes to high the blood vessels widen, called vasodilation, allowing the pressure to decrease.
Fun fact: An adult's body only contains about 4 to 6 liters of blood.
The cardiovascular system is truly a remarkable one. Without it, the rest of our body systems and organs wouldn't be able to function and we would cease to live so please be good to your heart and take care of your body so it can take care of you!
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