Heart as a Chosen Organ
The heart is the muscle representing the center of the human body’s circulation system, as it pumps the blood around the entire organism as it beats. The organ is the size of a fist and comprises four chambers made of muscle and powered by electrical impulses (Goodenough & McGuire, 2016). It is crucial to understand the main functions, composition, role in homeostasis, the types of tissues and cells involved, and other relevant information about the heart, as its role cannot be replaced in maintaining the body’s vitality.
Organ Description
The heart is located under the sternum within the thoracic section of the body, referred to as the mediastinum, which covers the space between the lungs. The organ is the approximate size of an adult’s fist and should weigh between two hundred and thirty and three hundred and fifty grams. The heart has an inverted cone shape, narrower at the bottom and wider at the top. Around 70% of the heart is located to the left of the body’s midline (Sheffield, 2023). It is part of the circulatory or cardiovascular system, which pumps blood from the heart to deliver oxygen to the lungs.
Within the circulatory system, the right ventricle of the heart (right pumping chamber) sends blood with lower oxygen content, which is why it is referred to as oxygen-poor blood, to the lungs. It goes through the pulmonary trunk and picks up the needed oxygen in the lungs. The role of the pulmonary veins is to transport the blood that receives oxygen into the left ventricle, or left chamber, the function of which is to pump blood out to transfer it to the arteries and the whole body. Blood collects and releases nutrients, hormones, and waste products when it moves through the body. Thus, the heart contributes to homeostasis by regulating the delivery of oxygen and nutrients to the tissues.
Tissue and Cell Types
The histological evaluation of the heart shows that the organ is predominantly made of cardiomyocytes and connective tissue. A cardiomyocyte is a contractible and excitable heart cell containing a central nucleus. Notably, the cell has unique sarcomeric isoforms of protein that set it apart from the rest of the muscle cells; besides, it contracts rhythmically without stopping (Keepers, Liu, & Quain, 2020).
Other cell types present in the heart include mesothelial, endothelial cells, and fibroblasts. Mesothelial cells form a membrane of simple squamous epithelial cells that have a mesodermal origin and form a lining of the pericardium, which is located around the heart. Endothelial cells create a single layer of cells that line all vessels and help regulate the exchange between the bloodstream and the surrounding tissues.
The heart’s connective tissue, the pericardium, has two layers that form a sac enclosing the heart (Goodenough & McGuire, 2016). While the fibrous pericardium forms the outer layer, the serous pericardium forms the inner layer of the organ (Goodenough & McGuire, 2016). The space between the two layers is called the pericardial cavity, which includes serous fluid and allows for the heart’s pumping action.
The heart’s cardiac muscle tissue is crucial to the organ’s functioning. It allows for unified contractions, allowing the heart to pump and transport blood through the body’s circulatory system. Importantly, the cardiac tissue can only be found in the heart, which contracts in a coordinated manner to allow blood pumping (Goodenough & McGuire, 2016).
The heart’s cardiac muscle performs the pumping action through unique cells called pacemaker cells. They are specific myocardial cells that allow for the heart’s contraction. The nervous system is responsible for sending signals to pacemaker cells and makes them either increase or decrease the heart rate (Keepers et al., 2020). Moreover, pacemaker cells are linked to the cardiac muscle cells, which allows them to transfer signals, resulting in a contraction wave sent to the cardiac muscle, thus creating the heartbeat.
Organ Failure
The tissue from which the heart is made plays a crucial role in the organ’s function. Significantly, in case of a heart attack, the heart cannot regenerate its muscle, which is when cardiac muscle is replaced by scar tissue (Keepers et al., 2020). The scar tissue cannot contribute to the contracting force of the organ, which is why the rest of the cardiac muscle tissue is subject to higher levels of hemodynamic burden (Goodenough & McGuire, 2016).
Consequently, if more scar tissue is created, the heart’s ability to contract reduces, which leads to compromised homeostasis and even death. Because of this, it is crucial to maintain the heart in good health, thus ensuring no loss of contractile myocardium and the subsequent formation of scar tissue. For example, if the heart were only made of connective tissue, it would have no capacity to contract and thus would not pump the blood to get oxygenated and transfer nutrients throughout the body.
References
Goodenough, J., & McGuire, B. (2016). Biology of humans: Concepts, applications, and issues (6th ed.). Pearson.
Keepers, B., Liu, J., & Qian, L. (2020). What’s in a cardiomyocyte – And how do we make one through reprogramming?. Biochimica et Biophysica Acta. Molecular Cell Research, 1867(3), 118464. Web.
Sheffield, S. A. (2023). The location, size, and shape of the heart. Web.