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The blood flow though the heart can be a very difficult concept to master. These easy to understand instructions will guide you through the heart and provide very specific details to help you in your goal of understanding how the heart works.
We will start with blood coming into the heart through two different veins. These veins are called the cranial and caudal vena cava. The cranial vena cava comes from the upper part of the body, while the caudal vena cava comes from the lower part of the body. They both carry the already used, de-oxygenated blood to the heart and empty this blood into the right atrium.
The right atrium has a unique structure of its own. Its wall is composed of web-like muscles called pecinate muscles. Other structures within the atrium include the sinus venarium, interatial septum, and the fossa ovalis. These structures are not significant for blood flow, thus will not be discussed. A structure that is of interest within the atrium is the intervenous tubercle. This is a small ridge of tissue between the point where the vena cava meet at the atrium, thus pushing the blood in a particular direction, this direction being through the right AV Valve (atrioventricular valve).
The right AV valve is the valve that pushes blood from the right atrium and into the right ventricle. The structure of the valve includes chordae tendineae, which anchor the cusps of the valve by papillary muscles within this atrioventricular orifice (opening between the two chambers of the heart). The right ventricle is fairly simple with its main feature being the trabeculae carnae, which are ridges within the interior of the ventricle.
Next the blood will be transported out of the right ventricle, through another valve, the pulmonary valve, and into pulmonary arteries. This is where the blood becomes transported to the lungs for gas exchange. This is the very important part where the respiratory system and the circulatory system function together to sustain a vital life process.
After gas exchange occurs in the lungs, the blood is now oxygenated and ready to be supplied back to the body for use. It re-enters the heart from the lungs through the pulmonary veins. It then drains into the left atrium. The left atrium does not contain the same structures as the right. It still has pectinate muscles, but it does not contain the rest of the structures as mentioned above.
The blood then flows through the left AV valve, which has the same basic structure as the right. Now the blood is contained in the left ventricle. From here, it will be pumped through the aortic valve and into the aorta. The blood has now begun to spread itself thoughout the entire body though the aorta. The aorta gives off many branches to different parts of the body. It begins with branches to the upper part and the aorta itself branches back and runs back down (descending aorta) all the way to its termination at the median sacral artery.
In conclusion, the heart is a very vital part of life as we know it. And understanding how it works and what is involved in the process is extremely important and well worth the time it takes to learn it!