a. Identify how the structure of each of the four tissue types contributes to the overall function of the organ/ body system;
The heart consists of 3 main layers, such as the Endocardium as the inner layer of the heart, the Myocardium which consists of the middle layer and the Epicardium as the outer layer of the heart. All of which are made up of four main tissue types such as muscle, epithelial, connective and nervous tissue (Gartner, 2020). Muscle tissue consists of three subtypes, such as smooth, skeletal, and cardiac muscle. The Myocardium layer of the heart is made up of this muscle tissue, primarily the cardiac muscle (McKinley, 2018). The cardiac muscle cells are found in thick bundles within the heart wall and are longitudinally split into a small number of branches, the ends of which are joined to adjacent muscle cells at junctions called intercalated discs (McKinley, 2018). These discs are unique to cardiac muscle and provide anchorage points for the myofibrils, which permit extremely rapid spread of contractile stimuli. The adjacent fibres are therefore triggered to contract simultaneously, acting as a functional syncytium (Young, et. al., 2014). Cardiac muscle cells are stimulated by an autorhythmic pacemaker, which branches throughout the organ and therefore coordinating contraction of the myocardium in each cardiac cycle (Young, et. al., 2014). The Endocardium which covers the internal surface and external surfaces of the heart, is composed of simple squamous epithelium and an underlaying layer of areolar connective tissue. The epithelial layer is continuous with the epithelial layer called the endothelium, which lines blood vessels. The Epicardium, also known as visceral layer of serous pericardium, as the outermost layer of the heart, is also made up of simple squamous epithelium and areolar connective tissue (McKinley, 2018). The areolar (loose) connective tissue is where coronary vessels, nerves and ganglia sit. Fat is also stored on this outer layer of the heart. The two layers of pericardium and loose connective tissue enclose the pericardial cavity, which is an area of small serous fluid for lubricating the serous layer of the visceral pericardium and provides friction-free contractions of the heart (Gartner, 2020). Internally, the heart is supported by a fibrous skeleton, which is composed of dense irregular connective tissue. It provides both structural support and acts as an electric insulator.
b. Discuss how dysfunction of two of these tissue types may alter the homeostatic mechanism/s underpinning the organ’s function/s;