Question

Veins allow blood to flow only______
A. Towards heart
B. Towards lungs
C. Towards kidney
D. Towards liver

Answer 1

Blood vessels are elastic tubes that carry blood, associated with oxygen and carbon dioxide, nutrients, water, and hormones throughout the body. Vessel networks carry blood to all tissues in a directed and regulated manner. Capillaries consist of a single layer of endothelium and associated connective tissue. These are made up of tiny arteries and veins.

Complete answer:
(A) Towards heart- Veins transport blood that has been depleted of oxygen back to the heart.
(B) Towards lungs- Pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.
(C) Towards kidneys- There are two renal veins, a left renal vein and a right renal vein. They branch off into the inferior vena cava and drain oxygen-less blood from the kidneys. As they enter into the kidneys, each vein divides into two parts.
(D) Towards liver- The liver has the supply of two large blood vessels, the hepatic artery and the portal vein. The hepatic artery transports blood from the aorta to the liver, whereas the portal vein transports blood containing the digested nutrients from the complete gastrointestinal tract, and also from the spleen and pancreas to the liver.

So, the correct answer is option (A) Towards heart.

Veins contain valves that ensure blood flows in the right and in one direction. They have thin walls and can frequently be injured, leading to varicose veins or other vein disease. Veins are generally close to the surface of the skin but do not give off a pulse. There are four types of veins, i.e., deep veins, superficial veins, pulmonary veins and systemic veins.
Some characteristics of arteries that differentiate it from veins are:
Arteries carry blood rich in oxygen away from the heart and to other parts of the body. Pulmonary arteries carry deoxygenated blood from the heart’s right ventricle to the lungs. Arteries do not have valves and depend on blood pressure to keep blood flowing in the right direction. Arteries have thicker muscular walls than the veins to withstand the high pressure of blood rushing through them. Arteries are usually present deeper in the body, but provide a detectable pulse. There are three types of arteries, including elastic arteries, muscular arteries and arterioles.

Note:
Arteries and veins are made up of three tissue layers. The thick outermost layer of a blood vessel is known as tunica adventitia or tunica externa and is made up of connective tissue. The middle layer of tunica media is thicker. It consists of circularly arranged elastic fibers, connective tissue, and smooth muscle cells. The inner layer also known as tunica intima is the thinnest layer, and it comprises a single layer of endothelium supported by a subendothelial layer.