The heart is undoubtedly the most vital organ in the human body. The heart is an organ, which is responsible for sending blood to organs for them to function correctly. Innerbody (2018) states that the placement of the heart is within the thoracic cavity. The heart is comprised of many different muscle tissues but the main and most abundant one being cardiac muscle Revisionworld.com (2018). Electrical impulses within the walls of the heart ensure that the pumping of the heart is rhythmic by causing the walls to contract according to Nhlbi.nih.gov. (2018). The blood that is pumped by the heart travels around the body providing oxygen and nutrients to cells and removes waste from them (ibid). Innerbody (2018) adds on by explaining the heart does this by receiving deoxygenated blood from the veins and directs it to the lungs to get oxygenated which, is followed by pumping the blood to other organs. Pdhpe.net (2018) writes that the heart belongs to the circulatory system and the pumping action is essential to maintain stable internal temperature and fight infections. However, if the heart were to stop operating then organs of the body would be forced to shut down. Lewis, T. (2016) further adds by stating the size of the heart tends to be around the proportion of a fist and can weigh between 280 to 340 and 230 to 280 grams in men and women respectively.
Innerbody (2018) shows that the heart is within the pericardial cavity, which is full of fluid. The fluid is useful for lubricating the heart to reduce friction with every heartbeat (ibid). New Health Advisor (2018) indicates that the pericardium is a thin membrane that holds the heart in place and also contains the fluid for lubrication. The sac containing the fluid is the parietal layer and holding the heart in place is the parietal layer (ibid). Innerbody (2018) explains the heart wall consists of three different layers. Epicardium being the outer most layer of the heart helps by protecting and lubricating the heart (ibid). New Health Advisor (2018) continues by claiming the second layer is the myocardium layer and contains the majority of the cardiac muscle tissues which handles the pumping action. The endocardium is the final layer of the heart, and the only purpose it serves is to keep the blood flowing smoothly inside the heart Innerbody (2018). Revisionworld.com (2018) illustrates that the heart is broken up into four chambers, left and right ventricles being at the bottom while left and right atria are up top. New Health Advisor (2018) notes that the atria are much smaller compared to the ventricles as they receive the blood and pump it to the ventricles. However, the ventricles are bigger because they need to pump the blood into the circulatory system. The right ventricle and atrium are smaller than the left counterparts as the right side pumps the blood up to the lungs and the left side sends the blood to the rest of the body (ibid). Nhsinform.scot (2017) observes that there are four valves in the heart. On the right side, there is the pulmonary and tricuspid valve, while the left side consists of the aortic and mitral valve (ibid). Innerbody (2018) follows up by writing that tricuspid and mitral valves are the Atrioventricular Valves (AV). Chordae tendinea are fibrous strings which attach the AV valves to the ventricles for them to not release the blood into the ventricles once they have pumped (ibid). New Health Advisor (2018) points out that pulmonary and aortic valve together are the semilunar valves. These valves are halfway of the ventricles and arteries (ibid).
Nhlbi.nih.gov (2018) states every pump of the heart is being controlled by its electrical system primarily known as the cardiac conduction system. The system contains three crucial sections. Present in the right atrium is sinoatrial (SA) node. Followed by the AV node in the septum near the tricuspid valve. Within the walls of the heart is His-Purkinje system (ibid). Ivyroses.com (2018) asserts that SA node contracts in a fashionable order, which creates an impulse that causes the contraction of the left and right atria. This function allows the blood flow from the atria to the ventricles by opening the valves needed (ibid). After this occurs, the AV node receives the impulse, and instead of causing contraction straight away it gives a short period where the blood will fill the ventricles writes Nhlbi.nih.gov (2018). After this occurs, the impulse follows the direction of the bundle of His and reaches a split point by the Purkinje fibres. Purkinje fibres are useful because it connects the signal directly to the cells of the ventricles (ibid). Ivyroses.com (2018) finishes the process by explaining that the action potential causes ventricle contraction causing the blood to be pumped through the arteries. Taking the blood to the lungs would be the pulmonary artery while the aorta allows blood flow through the rest of the body (ibid). Innerbody (2018) explains that certain events occur while the heart is beating. These actions are broken into three important stages. Revisionworld.com (2018) illustrates the first stage which is ventricular diastole and atrial systole. During this stage, the ventricles loosen up together leading to a lower pressure than the atrium. This action leads to the AV valves to open up for blood to rush in and semi-lunar valves to close for the unidirectional flow of blood (ibid). The second stage commences at the closing of the AV valves which is caused by the relaxation of the atria noted by New Health Advisor (2018).