Blood Vessel Structure and Function

How does the tunica media in veins differ from that in arteries?

• It is thicker with more smooth muscle

• It is thinner with less smooth muscle

• It has more elastic fibers

• It is absent in veins

Answer explanation

The tunica media in veins is thinner and contains less smooth muscle compared to arteries, which have a thicker tunica media with more smooth muscle to handle higher pressure from blood flow.

Why is the tunica externa thicker in veins compared to arteries?

• To withstand high pressure

• To support the vein and prevent collapse

• To increase blood flow

• To store blood

Answer explanation

The tunica externa is thicker in veins to support the vessel and prevent collapse, as veins operate under lower pressure compared to arteries. This structural support is crucial for maintaining vein integrity.

What is the role of veins in the circulatory system?

• To transport blood away from the heart

• To return blood to the heart

• To filter blood

• To store blood

Answer explanation

Veins play a crucial role in the circulatory system by returning blood to the heart after it has circulated through the body. This is essential for maintaining proper blood flow and ensuring that oxygen-depleted blood is sent back for reoxygenation.

What is the primary function of capillaries in the circulatory system?

• To pump blood throughout the body

• To exchange gases, nutrients, and waste products

• To store oxygen for later use

• To produce red blood cells

Answer explanation

The primary function of capillaries is to exchange gases, nutrients, and waste products between blood and tissues. They are the smallest blood vessels, allowing for efficient transfer of essential substances.

What role do precapillary sphincters play in the circulatory system?

• They produce red blood cells

• They regulate blood flow based on tissue needs

• They store nutrients for later use

• They remove waste products from the blood

Answer explanation

Precapillary sphincters are small muscles that regulate blood flow into capillaries based on the metabolic needs of tissues, ensuring that areas with higher demand receive more blood.

What is the role of capillaries in nutrient delivery?

• They store nutrients for future use

• They diffuse oxygen and nutrients into surrounding tissues

• They convert nutrients into waste

• They prevent nutrients from entering tissues

Answer explanation

Capillaries are tiny blood vessels that facilitate the exchange of oxygen and nutrients with surrounding tissues through diffusion, making them essential for nutrient delivery.

What is the primary function of the tunica intima in blood vessels?

• To provide structural support

• To facilitate smooth blood flow

• To store blood

• To regulate blood pressure

Answer explanation

The primary function of the tunica intima is to facilitate smooth blood flow. This inner layer of blood vessels reduces friction as blood moves through, ensuring efficient circulation.

How do valves in veins assist in blood circulation?

• They increase blood pressure

• They prevent backflow of blood

• They store excess blood

• They produce red blood cells

Answer explanation

Valves in veins prevent backflow of blood, ensuring it flows in one direction towards the heart. This is crucial for effective circulation, especially in the limbs where blood must travel against gravity.

What is the significance of the elasticity of arteries?

• To store nutrients

• To withstand high pressure and maintain blood flow

• To filter blood

• To produce white blood cells

Answer explanation

The elasticity of arteries is crucial as it allows them to withstand high pressure from the heart's pumping action and helps maintain continuous blood flow throughout the circulatory system.