Question

What is the largest blood vessel in the human body?

Answer 1

Blood is the major circulatory fluid in the body. Lymph is another body fluid which provides an important transport channel to selected materials. Both blood and lymph are in permeable contact with tissue fluid for exchange of materials with the body cells. Blood vessels are part of the cardiovascular system that transport blood throughout the body.

Complete answer:
There are three major types of blood vessels; veins, arteries, and capillaries.
Veins: Veins conveys blood from an organ toward the heart. Veins usually carry deoxygenated blood with the exception of pulmonary veins which carry oxygenated blood from lungs to the heart. Veins are generally superficial. They retain blood after death. Flow of blood is very slow but is smooth. Jerks are absent. Pressure is very low.
Capillaries: The blood vessels are very narrow with a diameter of 5-8 micrometer. It develops from terminal arterioles. A capillary allows passage of red blood corpuscles only in a single file. Capillary is specialized for exchange of materials between blood and tissue fluid.
Arteries: It is a vessel which carries blood from heart towards an organ. Arteries generally carry oxygenated blood with the exception of pulmonary arteries which pass deoxygenated blood to lungs for oxygenation. Internal valves do not occur . Lumen is comparatively narrow while the wall is thick, muscular and elastic.
The largest blood vessel/ largest artery is carotid systemic or dorsal aorta which is connected to the heart and extends down into the abdomen. It is a question mark shaped long vessel that arises from the left ventricle of the heart.

Note:
The aorta has many branches, and the branches subdivide repeatedly, with the subdivisions growing smaller and smaller in diameter. The smallest arteries are called arterioles. Blood flows under pressure inside an artery. The movement is jerky with alternate high pressure and low pressure corresponding to systolic and diastolic movements of the heart.