CIRCULATORY SYSTEM TYPES OF CIRCULATION, THEIR FUNCTIONS, AND DISEASE

. The circulatory system consists of blood, the heart and blood, and lymphatic vessels. Blood Is formed from stem cells in the bone marrow. The heart pumps blood through its four Chambers with the help of valves, which prevent backflow. A conducting system, composed of modified cardiac muscle cells, regulates the nature and frequency of the heartbeat. The Structure of the walls of large arteries provides the resiliency to modify the pressures of Blood leaving the heart so that blood flow is more even. Smooth muscle in the walls of Smaller arteries are also important in regulating blood pressure and the regional distribution of blood. Exchange of gasses and metabolites occurs in capillary beds throughout the body. A network of veins collects blood and returns it to the heart. Most of the blood volume resides in the veins. Lymphatic vessels collect tissue fluids and white blood cells and return them to the circulation through two major ducts. Homeostasis within the circulatory system is regulated by sensors in the carotid body and carotid sinus.