There are four main types of tissue: muscular, epithelial, connective and nervous. Each is made up of specialized cells grouped according to their structure and function. Muscle tissue varies depending on its function and location in the body. In mammals, the three types are: skeletal or striated muscles; smooth or non-striated muscle; and the heart muscle, sometimes called semi-striated. Smooth and cardiac muscles contract involuntarily, without conscious intervention. Epithelial tissue can have columnar, cuboidal, or squamous cell shapes. Epithelial tissue has bricks, or cells, of different shapes. There are columnar cells, which means “column-shaped cells”; cuboid cells, which are cube-shaped cells; and squamous cells, which are flattened, scale-like cells. Connective tissues include several types of fibrous tissue that vary only in their density and cellularity, as well as more specialized and recognizable variants: bones, ligaments, tendons, cartilage, and adipose tissue (fat). Nervous tissue or nervous tissue is the main tissue component of both parts of the nervous system; the brain and spinal cord of the central nervous system (CNS) and the branched peripheral nerves of the peripheral nervous system (PNS), which regulate and control bodily functions and activity. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay To me, the “wave” of depolarization is called the contractions of the heart that come and go regularly like a wave would. The pulmonary circulation is the circulation system that carries deoxygenated blood to the lungs and returns oxygenated blood from the lungs to the heart. The two blood vessels involved in pulmonary circulation are the pulmonary artery and the pulmonary vein. Deoxygenated blood flows into the right ventricle from the right atrium. This blood is transported to the alveoli of the lungs to be oxygenated by the pulmonary artery. The pulmonary artery, which branches immediately from the right ventricle, is called the pulmonary trunk. The pulmonary trunk divides in two; the left pulmonary artery and the right pulmonary artery. The left pulmonary artery carries blood to the left lung while the right pulmonary artery carries blood to the right lung. Carbon dioxide is removed from the blood while oxygen is absorbed into the blood at the alveolar capillaries. Oxygenated blood is carried to the left atrium of the heart by four pulmonary veins. A small amount of oxygenated blood is carried to the heart through the bronchial veins. Keep in mind: this is just a sample. Get a personalized article from our expert writers now. Get a Custom Essay Systemic circulation is the circulation system that carries oxygenated blood throughout the body and returns deoxygenated blood to the heart from body tissues. Oxygenated blood from the lungs returns to the left atrium of the heart through the pulmonary veins. This blood circulates in the left ventricle and exits the heart through the aorta. The aorta branches into small arteries that carry blood to different organs in the body. Within an organ or tissue, these arteries branch into arterioles, which constitute blood capillaries. The exchange of oxygen and nutrients with metabolizing cells occurs via blood capillaries. Carbon dioxide and other metabolic wastes are returned to the bloodstream. Deoxygenated blood returns to the Venules and returns to the right atrium of the heart through the vena cava. The deoxygenated blood of..