Muscular so that contraction can occur in various responses. B. Capillaries- see Fig. The middle layer of the vein is less developed the blood in the veins is under significantly less pressure, therefore veins must have valves to prevent backflow and keep the blood moving toward the heart at any one time the blood in the veins, and therefore they act as a reservoir and will constrict if a hemorrhage occurs, to prevent excessive bleeding if the valves weaken, then the individual will have varicose veins that will stick out. Heart - see Fig.
Nodal tissue has the characteristics of both muscle and nerve.
Contraction messages travel along Purkinje fibers to the muscle cells of the ventricles of the heart. Vascular Pathways - see Fig. Circulatory Disorders - see Fig. Ulceration leads to clot formation thromboembolism- clot developing, moving, blocking smaller vessel. Warning signs- numbness, temporary blindness heart attack portion of heart muscle dies due to lack of oxygen angina coronary artery partially blocked, pain in left arm and chest.