B2 - Blood Vessels

What is the function of arteries?

To carry blood at high pressure from the heart to the organs

Why do arteries have thick muscular walls?

To withstand the high pressure of the blood and control blood flow

What role do elastic fibers in arteries play?

They stretch when blood surges through and recoil between surges to keep blood moving smoothly

What causes the pulse you feel in arteries?

The surge of blood with each heartbeat stretching the artery walls

What two main types of tissue make arteries strong and elastic?

Thick muscle tissue and thick elastic tissue

What is the lumen of a blood vessel?

The hollow central space inside a blood vessel through which blood flows

How does the size of the lumen in arteries compare to veins?

Arteries have a narrow lumen to maintain pressure; veins have a wider lumen to allow easier blood flow at low pressure

How does the thickness of artery walls compare to the size of their lumen?

Arteries have thick walls compared to their narrow lumen

What happens to blood once it reaches the organs?

It flows through capillaries where substances are exchanged between blood and body cells

What substances diffuse from the blood to body cells in capillaries?

Glucose and oxygen diffuse into cells

What substances diffuse from body cells to the blood in capillaries?

Carbon dioxide diffuses into blood

Why do capillaries have very thin walls?

To create a short diffusion pathway for fast exchange of substances

How are capillaries adapted for efficient exchange?

They have walls only one cell thick and are permeable to allow easy diffusion

Why do capillaries have a tiny lumen?

Because they are very small to increase surface area for exchange

What is meant by the total cross-sectional area of capillaries?

The combined surface area of all capillaries added together, which is very large

How does the large total cross-sectional area of capillaries affect blood pressure and flow?

It lowers blood pressure and slows blood flow, allowing time for exchange with tissues

Why is blood flow slower in capillaries compared to arteries?

Because capillaries have a much larger total cross-sectional area, reducing pressure and speed

What is the main function of veins?

To carry blood back to the heart at low pressure

How do vein walls compare to artery walls?

Vein walls are thinner with less muscle and elastic tissue than arteries

Why do veins have thin walls?

Because the blood pressure in veins is low and walls don't need to be thick

Why do veins have larger lumens than arteries?

To allow easier blood flow at low pressure

What special structures do veins contain to prevent blood flowing backwards?

Valves

What is the function of valves in veins?

To prevent backflow of blood and ensure it moves towards the heart

How do valves in veins work when blood flows in the correct direction?

Valves open to allow blood through

How do valves in veins work when blood tries to flow backwards?

Valves close to stop the backflow

What happens to blood pressure as blood moves from arteries to capillaries to veins?

Blood pressure decreases progressively from arteries to veins

Why is blood pressure low in veins compared to arteries?

Because blood loses pressure after passing through organs and capillaries

What problem might occur if veins did not have valves?

Blood could pool or flow backwards, reducing circulation efficiency

How does the structure of arteries help handle blood surges?

Thick muscular walls and elastic fibers allow arteries to stretch and recoil, maintaining steady blood flow

How do capillaries' structure maximize diffusion efficiency?

Thin walls and a large surface area allow rapid exchange of gases and nutrients between blood and cells

How does the structure of arteries relate to their function?

Thick, strong, elastic walls help arteries handle high pressure and pulse from the heart

How does the structure of capillaries relate to their function?

Thin, permeable walls and small size allow efficient exchange of substances with tissues

How does the structure of veins relate to their function?

Thin walls and valves accommodate low pressure and prevent backflow of blood

How do you calculate the rate of blood flow?

Divide the volume of blood by the time taken (Rate = volume/time)

Calculate the rate of blood flow if 2500 ml passes through the aorta in 8 minutes.

2500 ml ÷ 8 min = 312.5 ml/min (rounded to 320 ml/min)