Tham khảo tài liệu 'medical physiology rhoades tanner - part 4', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 12 An Overview of the Circulation and Hemodynamics 211 SVC IVC spleen Lungs Endocrine glands Coronary circulation Liver Portal vein Stomach Intestines pancreas Bronchial circulation Pulmonary artery. Pulmonary vein ----Arms and trunk skin muscle and bone Head brain skin and bone Endocrine glands ---------------- Kidneys __ Kidneys tubules glomeruli A model of the cardiovascular system. The right and left hearts are aligned in series as are the systemic circulation and the pulmonary circulation. In contrast the circulations of the organs other than the lungs are in parallel that is each organ receives blood from the aorta and returns it to the vena cava. Exceptions are the various portal circulations which include the liver kidney tubules and hypothalamus. SVC superior vena cava IVC inferior vena cava RA right atrium RV right ventricle LA left atrium LV left ventricle. Trunk and legs skin muscle and bone consistent pressure and driving blood to the small arteries and arterioles. Smooth muscle in the relatively thick walls of small arteries and arterioles can contract or relax causing large changes in flow to a particular organ or tissue. Because of their ability to adjust their caliber small arteries and arterioles are called resistance vessels. The prominent pressure pulsations in the aorta and large arteries are damped by the small arteries and arterioles. Pressure and flow are steady in the smallest arterioles. Blood flows from arterioles into the capillaries. Capillaries are small enough that red blood cells flow through them in single file. They are numerous enough so that every cell in the body is close enough to a capillary to receive the nutrients it needs. The thin capillary walls allow rapid exchanges of oxygen carbon dioxide substrates hormones and other molecules and for this reason are called exchange vessels. Blood flows from capillaries into venules and small veins. These vessels have larger diameters and thinner walls than the .
