The pulmonary circulation takes deoxygenated blood from the right ventricle to the lungs, where it is reoxygenated and returned to the left atrium (Applegate, 2000, 247-248). From here it passes into the left ventricle. The systemic circulation pumps blood from the left ventricle out to the rest of the body, where it delivers oxygen to the tissues and picks up carbon dioxide for discharge from the body by the lungs. It returns the deoxygenated blood to the right atrium. From here the blood passes into the right ventricle and into the pulmonary circulation.
30.12 A thrombus in the anterior descending branch of the left ventricle coronary artery might cause sudden death because this artery supplies blood to most of the left myocardium in the left ventricle (Applegate, 2000, 248). If the blood supply to this muscle is obstructed by a thrombus, the heart could not pump blood to the body and so death would ensue quickly. The thrombus would cause a lethal heart attack.
30.13 Cardiac muscle cells are elongated and branching, with one or two nuclei per cell (Applegate, 2000, 244-245). They appear striated because of the arrangement of their myofibrils. The cells are connected to each other by intercalated discs and gap junctions, and are arranged around the heart in a spiral fashion to form the myocardium. Skeletal muscle are made up of hundreds of muscle fibers bundled together and wrapped in connective tissue (123-124). Each muscle is covered with a connective tissue sheath. Each skeletal muscle fiber is a single cylindrical cell; its membrane is called the sarcolemma, and its cytoplasm is the sarcoplasm. It contains specialized smooth endoplasmic reticulum. There are multiple nuclei at the periphery of the cell, and the cells contain many mitochondria. Microscopically, the cells have alternating light (I) and dark (A) bands which are seen as striations. The sarcoplasm contains thick myofilaments of myosin and thi...