Problem 87 - Objective Biology for NEET

Question

In mammals, veins differs from arteries in having (a) Thicker walls (b) Deeply present (c) Carry blood away from heart (d) Internal valves

Step-by-Step Solution

Answer

(d) Internal valves

Step 1: Identify the properties of veins and arteries

In order to solve this exercise, an understanding of the basic properties of veins and arteries is required. Arteries are blood vessels that carry blood away from the heart and have thicker walls to withstand the pressure of the blood being pumped directly from the heart. Veins, on the other hand, carry blood toward the heart and are typically closer to the surface of the skin. They have thinner walls, and they contain internal valves to aid the return of blood to the heart.

Step 2: Compare options with known properties

Now evaluate each statement given in the options in relation to the understanding of veins and arteries. \n(a) Thicker walls - This is a characteristic of arteries, not veins. This is incorrect.\n(b) Deeply present - Veins are typically closer to the skin's surface while arteries are deeper within the body. This statement is incorrect.\n(c) Carry blood away from heart - This is a characteristic of arteries, not veins. This is incorrect.\n(d) Internal valves - Veins have internal valves to help the blood flow back to the heart. This statement is correct.

Key Concepts

Veins vs Arteries

When comparing veins and arteries, a key distinction is their direction of blood flow and structural adaptations to their roles in the circulatory system. Arteries carry oxygen-rich blood away from the heart, except for the pulmonary arteries which carry deoxygenated blood to the lungs. They possess thicker walls made up of smooth muscle and elastic tissue, designed to handle high pressure as the heart pumps blood into them.

Veins, in contrast, carry blood towards the heart. Given that the pressure in veins is much lower, their walls are thinner and less muscular. However, they have a crucial feature—internal valves. These valves prevent the backflow of blood, ensuring it moves in one direction, back to the heart. Unlike arteries, most veins are superficial and can often be seen under the skin, particularly in the arms and legs. These differences in structure and function between veins and arteries play a vital role in the systemic and pulmonary circuits of blood flow.

Blood Vessel Structure

Blood vessels are the highways of the circulatory system, with their structure tailored to their specific function. The blood vessel structure typically comprises three layers: the innermost layer called the tunica intima, the middle layer known as the tunica media, and the outer layer called the tunica externa or adventitia.

The tunica intima is lined with endothelial cells that provide a smooth surface for blood to flow over. The tunica media is made up of smooth muscle and elastic fibers, which allows vessels like arteries to expand and contract, regulating blood pressure and flow. The tunica externa, composed mainly of connective tissue, provides structure and protection to the vessel. Veins have a similar three-layered structure but are notable for their thinner tunica media and the presence of valves within the tunica intima, which is a key feature differentiating them from arteries.

Cardiovascular Physiology

Cardiovascular physiology focuses on the functions of the heart and blood vessels within the circulatory system. The heart serves as the pump, moving blood through the body to deliver nutrients and remove waste. The arteries and veins play specialized roles within this system. Arteries respond to the rhythmic pumping of the heart by expanding and contracting, a phenomenon known as pulse.

Meanwhile, veins work to return deoxygenated blood back to the heart under much lower pressure. The low pressure in veins is offset by the skeletal muscle pump—a mechanism where skeletal muscle contractions compress veins, aiding in blood flow back to the heart. Some parts of this physiology can be felt in our daily lives, such as feeling our pulse in an artery or the effects of standing up quickly, which challenges our cardiovascular system to rapidly adapt to maintain blood flow to the brain.