3.3.4.1: Blood vessels and tissue fluid

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

• To carry blood away from the heart

• To carry blood towards the heart

• To exchange gases and nutrients

• To store blood

Answer explanation

The primary function of arteries is to carry blood away from the heart, delivering oxygen-rich blood to various parts of the body. This distinguishes them from veins, which carry blood towards the heart.

Which structural feature of arteries helps them withstand high pressure?

• Thin walls

• Thick muscular walls

• Valves

• Large lumen

Answer explanation

Arteries have thick muscular walls that allow them to withstand high pressure from the blood pumped by the heart. This structural feature provides strength and elasticity, enabling arteries to maintain their shape and function effectively.

What is the main function of arterioles in the circulatory system?

• To act as a reservoir for blood

• To regulate blood flow to capillaries

• To exchange gases and nutrients

• To return blood to the heart

Answer explanation

The main function of arterioles is to regulate blood flow to capillaries. They control the amount of blood that enters the capillary beds, thus influencing nutrient and gas exchange in tissues.

How do veins differ structurally from arteries?

• Veins have thicker walls

• Veins have valves

• Veins have a smaller lumen

• Veins carry oxygenated blood

Answer explanation

Veins differ from arteries primarily by having valves, which prevent backflow of blood. This is crucial as veins carry deoxygenated blood back to the heart, often against gravity, unlike arteries that have thicker walls and carry oxygenated blood.

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

• To transport blood at high pressure

• To exchange gases, nutrients, and waste products

• To store blood

• To regulate blood pressure

Answer explanation

The primary role of capillaries is to facilitate the exchange of gases, nutrients, and waste products between blood and tissues, making this option the correct choice.

Why are capillary walls only one cell thick?

• To provide structural support

• To allow rapid diffusion of substances

• To prevent blood loss

• To increase blood pressure

Answer explanation

Capillary walls are only one cell thick to allow rapid diffusion of substances, such as oxygen and nutrients, between blood and surrounding tissues. This thin structure facilitates efficient exchange, which is crucial for cellular function.

What is the significance of capillary beds in the circulatory system?

• They increase blood pressure

• They provide a large surface area for exchange

• They store oxygen

• They transport hormones

Answer explanation

Capillary beds are crucial as they provide a large surface area for exchange of gases, nutrients, and waste between blood and tissues, facilitating efficient cellular function.

What is tissue fluid, and how is it formed?

• A fluid that carries oxygen, formed by the liver

• A fluid that surrounds cells, formed by filtration from capillaries

• A fluid that transports hormones, formed by the kidneys

• A fluid that stores nutrients, formed by the pancreas

Answer explanation

Tissue fluid is a fluid that surrounds cells, formed by the filtration of blood plasma through capillary walls. This process allows nutrients and oxygen to reach cells while removing waste products.

How does tissue fluid return to the circulatory system?

• Through the lymphatic system

• Directly into veins

• Through the digestive system

• By evaporation

Answer explanation

Tissue fluid returns to the circulatory system primarily through the lymphatic system. The lymphatic vessels collect excess tissue fluid, which is then transported back into the bloodstream, ensuring fluid balance in the body.

What role do valves in veins play in the circulatory system?

• They increase blood pressure

• They prevent backflow of blood

• They regulate heart rate

• They store blood

Answer explanation

Valves in veins play a crucial role by preventing backflow of blood, ensuring that it flows in one direction towards the heart. This is essential for maintaining efficient circulation, especially in the lower extremities.