Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 251 19.12 Chapter Nineteen Review An introduction to the cardiovascular system: • The blood vessels can be categorized into the pulmonary circuit (which carries blood to and from the lungs) and the systemic circuit (which transports blood to and from the rest of the body). • Arteries carry blood away from the heart; veins return blood to the heart. Capillaries, or exchange vessels, are thin-walled, narrow-diameter vessels that connect the smallest arteries and veins. • The heart contains four chambers: the right atrium and right ventricle, and the left atrium and left ventricle. The heart is a four-chambered biological structure, supplied by the coronary circulation, which pumps oxygen-poor blood to the lungs and oxygen-rich blood to the rest of the body: • The pericardial cavity surrounds the heart, which lies within the anterior portion of the mediastinum, which separates the two pleural cavities. • The pericardium lines the pericardial cavity. The visceral pericardium (epicardium) covers the heart’s outer surface, and the parietal pericardium lines the inner surface of the pericardial sac, which surrounds the heart. • The coronary sulcus, a deep groove, marks the boundary between the atria and the ventricles. Other surface markings also provide useful reference points in describing the heart and associated structures. • Most of the heart consists of the muscular myocardium. The endocardium lines the inner surfaces of the heart, and the epicardium covers the outer surface. • Cardiac muscle cells are interconnected by intercalated discs, which convey the force of contraction from cell to cell and conduct action potentials. • The atria are separated by the interatrial septum, and the ventricles are divided by the interventricular septum. The right atrium gets blood from the systemic circuit via two large veins, the superior vena cava, and the inferior vena cava. (The atrial walls contain the pectinate muscles and prominent muscular ridges.) • Blood flows from the right atrium into the right ventricle via the right atrioventricular (AV) valve (tricuspid valve). This opening is bounded by three cusps of fibrous tissue braced by the chordae tendineae, which are connected to papillary muscles. • Blood leaving the right ventricle enters the pulmonary trunk after passing through the pulmonary valve. The pulmonary trunk divides to form the left and right pulmonary arteries. • The left and right pulmonary veins return blood from the lungs to the left atrium. Blood leaving the left atrium flows into the left ventricle via the left atrioventricular (AV) valve (bicuspid, or mitral, valve). Blood leaving the left ventricle passes through the aortic valve and into the systemic circuit via the ascending aorta. • Anatomical differences between the ventricles reflect the functional demands placed on them. The wall of the right ventricle is thin, whereas the left ventricle has a massive muscular wall. of 368