Species range in size from the hefty Common Raven (Corvus corax), at 1.5 kg (3 lb 5 oz) and 70 cm (2 ft 3 in), to the diminutive Short-tailed Pygmy Tyrant (Myiornis ecaudatus), at just 4.2 g (0.14 oz) and 6.5 cm (2 Â½ in).
The heart receives its own supply of blood from the coronary arteries. Two major coronary arteries branch off from the aorta near the point where the aorta and the left ventricle meet. These arteries and their branches supply all parts of the heart muscle with blood.hen the coronary arteries narrow to the point that blood flow to the heart muscle is limited (coronary artery disease), collateral vessels may enlarge and become active.
The circulatory system is made up of the heart and blood vessels. The heart pumps oxygen-rich blood through vessels called arteries. Veins carry blood from various parts of the body back to the heart. Arteries and veins are connected by tiny capillaries (KAP'ih-laireez). The heart's right side receives dark bluish blood from the superior and inferior vena cava. (The superior vena cava is the large vein that brings blood back from the upper part of the body. The inferior vena cava is the vein that brings blood from the lower body.) The heart's right side pumps this blood to the lungs. There, waste gas (carbon dioxide) is removed and oxygen is picked up. The bright red oxygenated blood returns to the heart's left side.