Component 3.2 - Mammalian Circulation Flashcards Preview

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Flashcards in Component 3.2 - Mammalian Circulation Deck (14)
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1
Q

Why is double circulation in a mammal more efficient than single circulation in a fish?

A

Because oxygenated blood can be pumped around the body at higher pressure

2
Q

What is the innermost layer of a blood vessel and what is its function?

A

Endothelium - it is one cell thick and is surrounded by the tunica intima.

It is a smooth lining, reducing friction with a minimum resistance to blood flow

3
Q

What is the middle layer of the blood vessel and what is it made up of?

A

The tunica media - contains elastic fibres and smooth muscle

4
Q

Why is the tunica media thicker in arteries than in veins?

A

Elastic fibres stretch and recoil, pushing blood through the artery. This maintains blood pressure as the blood is transported further from the heart.

5
Q

What is the outer layer of the blood vessel called? What is it made of?

A

Tunica externa - it contains collagen fibres, which resist overstretching

6
Q

What is the function of arteries?

A

Carry blood away from the heart. Their thick muscular walls withstand the pressure of the blood derived from the heart.

Arteries -> Arterioles -> Capillaries

7
Q

How do capillaries help return blood to the heart?

A

Blood from the capillaries collects into venules, which take blood into veins.

8
Q

How are veins different to arteries?

A

1) They have valves
2) They have a larger diameter lumen
3) Thinner walls with less muscle than arteries - blood pressure and flow rate are lower

9
Q

How does blood return to the heart from veins?

A

For veins above the heart, blood returns to the heart by gravity and for other veins it moves by the pressure from surrounding muscles.

10
Q

Describe the structure of capillaries

A

They have thin walls, which are only one layer of endothelium on a basement membrane.

There are pores between the cells making the walls permeable. So exchange of substances such as glucose and water can take place between blood and tissues.

11
Q

How do capillaries function?

A

Capillaries reduce the rate of blood flow due to friction against their wall and this means that there is plenty of time for the exchange of materials.

12
Q

Why can the heart be thought of as two separate pumps?

A

One deals with oxygenated blood - pumping blood to the rest of the body.

One deals with deoxygenated blood - pumping blood to the lungs.

13
Q

What is the heart made of and why is this suitable?

A

It consists largely of cardiac muscle, a specialised tissue which can relax and contract rhythmically of its own accord.

It is involuntary muscle and unlike voluntary muscles it never tires.

14
Q

How can heart rate be modified?

A

By nervous and hormonal stimulation

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