Blood Circulation System - Essay Example

Blood Circulation
These create the top chambers or the atrium (atria in plural) and the bottom chambers or the ventricles (Sherwood, 2012). The atrium is considered as a holding chamber, and the pumping chambers are the ventricles. As the name suggests, each of the halves creates a separate system that has to work in sync for one to continue living healthily. Blood flows to the ventricles from the atria and never across the halves, thanks to the septum (Solomon, Berg and Martin, 2010).

For the effective flow of blood from the top chambers to the bottom chambers, openings called valves are present. They operate like trapdoors as they allow blood flow only in one direction to avoid a situation where blood would flow back to the atrium. These valves are not only present inside the walls separating the chambers, but also on the large arteries that are responsible for the carrying of blood to the organs from the heart. These arteries are the pulmonary arteries and the aorta. While still at it, it is necessary to note that the pulmonary artery is the only artery that carries deoxygenated blood while the other arteries carry oxygenated blood (Solomon, Berg, and Martin, 2010). Once the blood has been pumped from the ventricles, the valves allow it to get out and close to avoid it flowing back into the heart. The arteries are the largest blood vessels in the human body, and since they cannot be used to supply blood everywhere, they are divided into various sizes, which lead to the formation of blood vessels. The smallest are referred to as the capillaries which are used to make an intricate set of connections of little vessels all over different muscles and parts of the body. Several capillaries form veins, which in turn form larger veins that empty blood into the heart, and the cycle continues. This is called blood circulation (Sherwood, 2012).

The main aim of blood circulation is to supply oxygen-rich blood to all the organs and tissues in the body. This happens in two cycles. The first one is a systematic cycle where blood is transported to every section of the body, and carbon dioxide is collected amongst other waste from these areas. The pulmonary cycle circulates blood to the lungs and from it to aid in the release of carbon dioxide and bring in oxygenated blood. The systematic cycle takes place in the left region of the heart while the right side handles the pulmonary cycle. The mitral valve at the upper part of the left-side chamber is pressed open by blood and allows it to trickle down to the left ventricle (Sherwood, 2012). The blood is then pumped directly into the aorta and is rich in oxygen. It is then transported to all other parts of the body and organs. Used blood is then collected back to the heart through two main veins. One is the inferior vena cava, which takes blood to the heart from the lower body sections. The other is the superior vena cava, which collects blood from the upper body. These two drain the blood into the upper right chamber (Solomon, Berg, and Martin, 2010).

Blood, from there, picks up the pulmonary cycle and gets to the right lower chamber from the right upper chamber. The blood is forced into the pulmonary artery which is divided into two: one part to the right and the other to the left lungs. The pulmonary veins carry the rich oxygen blood back to the left atrium, and the cycle continues. These two processes, though seemingly sequential, happen simultaneously, with the two atria being the first to contact as they push blood to the ventricles (Sherwood, 2012). The ventricles, on the other hand, contract and drive the blood into the aorta and pulmonary artery. The muscles inside the heart then relax to let the bloodstream in and fill up the upper chamber again from the veins. This forms the heartbeat and a healthy person is considered to have a heartbeat rate of 72 per minute.

There is a group of cells that has the ability to generate electrical activity on their own. They separate charged particles where certain charged particles are spontaneously leaked into the cells producing electric impulses in what is referred to as pacemaker cells causing the heart to contract. They produce these charges at least more than once in a second to produce the normal heartbeat rate of 72 beats per minute according to Solomon, Berg, and Martin 

2010). The pacemaker cells include the natural pacemaker, or the sinoatrial node, which is located in the right upper chamber, and the atrioventricular node, situated at the right lower chamber. The electrical impulses present from the right are transferred to the Bundle of His, and then to the branches on both sides before being spread rapidly using the Purkinje fibers across the two halves (Sherwood, 2012). This leads to simultaneous contractions; hence the flow of blood. Being a natural pacemaker, the sinoatrial node generates electrical impulses faster than the rest of the nodes and thus controls the whole system. They help in the regulation of the heartbeat rate.