Question

Match the descriptions to the blood vessel in the key. Answers may be used more than once. Key: a. venules b. veins c. capillaries d. arteries e. arterioles Take blood away from the heart

Short answer

The blood vessel that takes blood away from the heart is d. arteries.

Step-by-step solution

Identify the blood vessel taking blood away from the heart.

Among the blood vessels listed in the key, arteries are the ones responsible for carrying blood away from the heart. Blood in the arteries is usually oxygenated, except for the pulmonary artery, which carries deoxygenated blood from the heart to the lungs for oxygenation. So, the answer is: d. arteries

Key concepts

Blood Vessels

Blood vessels are the network of tubes that transport blood throughout the body's tissues. They are essential components of the circulatory system, which also includes the heart and blood. Blood vessels ensure that every cell receives the necessary nutrients and oxygen, while also helping to remove waste products. This complex system contains three primary types of blood vessels, each serving a distinct function:

• Arteries - Carry oxygen-rich blood away from the heart, except for the pulmonary artery.
• Veins - Return deoxygenated blood back to the heart.
• Capillaries - Connect arteries and veins, facilitating the exchange of oxygen, carbon dioxide, and other substances between blood and tissues.

Understanding these different types of blood vessels is key to grasping how oxygen and nutrients circulate through the body.

Arteries

Arteries are large, robust blood vessels that play a critical role in the circulatory system by transporting blood away from the heart. They are characterized by thick, muscular walls that help manage the high pressure exerted by the beating heart. This strength is essential for maintaining a constant flow of blood throughout the body's various regions. Besides their strength, arteries have a unique elasticity. This allows them to expand when blood is pumped into them and then recoil, helping to push the blood onward. Elastic arteries, such as the aorta, are closest to the heart and can handle the pulsatile pressure easily. Further away, arteries become muscular and are more involved in directing blood flow. In summary, arteries are vital for:

• Carrying oxygenated blood away from the heart, except in pulmonary circulation.
• Handling high pressure from the heart's pumping action.
• Regulating blood flow through contraction and relaxation of their muscular walls.

Veins

Veins are the blood vessels that carry blood back to the heart from the rest of the body, typically transporting deoxygenated blood. Unlike arteries, veins operate under lower pressure and have thinner walls. However, they have larger lumens (the hollow inside where blood flows) to accommodate and assist the return of blood to the heart. A unique feature of veins is their one-way valves. These valves prevent the backward flow of blood, ensuring it travels in only one direction towards the heart. This is particularly important in the limbs, where blood needs to move against gravity. Key characteristics of veins include:

• Transporting deoxygenated blood to the heart, except for pulmonary veins which carry oxygenated blood from the lungs.
• Having valves to prevent backflow of blood.
• Operating under low pressure with wider lumens to facilitate blood return.

Capillaries

Capillaries are the smallest and most numerous blood vessels, acting as the main sites for the exchange of oxygen, carbon dioxide, nutrients, and waste between blood and tissues. Their walls are extremely thin - only one cell thick - which allows for efficient diffusion of substances in and out of surrounding tissues. Because they connect the arterial and venous systems, capillaries form an extensive network that reaches almost every cell in the body. This widespread network ensures cells can receive oxygen and nutrients and dispose of carbon dioxide and other metabolic wastes rapidly. The role of capillaries can be summarized as:

• Facilitating the exchange of gases, nutrients, and waste products.
• Connecting the arterial and venous circuits.
• Providing a vast surface area for effective diffusion due to their extensive number and very thin walls.

Understanding capillaries is crucial for appreciating how substances circulate and nourish our body at the cellular level.